1 // SPDX-License-Identifier: GPL-2.0-only
5 * Runtime locking correctness validator
7 * Started by Ingo Molnar:
9 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
12 * this code maps all the lock dependencies as they occur in a live kernel
13 * and will warn about the following classes of locking bugs:
15 * - lock inversion scenarios
16 * - circular lock dependencies
17 * - hardirq/softirq safe/unsafe locking bugs
19 * Bugs are reported even if the current locking scenario does not cause
20 * any deadlock at this point.
22 * I.e. if anytime in the past two locks were taken in a different order,
23 * even if it happened for another task, even if those were different
24 * locks (but of the same class as this lock), this code will detect it.
26 * Thanks to Arjan van de Ven for coming up with the initial idea of
27 * mapping lock dependencies runtime.
29 #define DISABLE_BRANCH_PROFILING
30 #include <linux/mutex.h>
31 #include <linux/sched.h>
32 #include <linux/sched/clock.h>
33 #include <linux/sched/task.h>
34 #include <linux/sched/mm.h>
35 #include <linux/delay.h>
36 #include <linux/module.h>
37 #include <linux/proc_fs.h>
38 #include <linux/seq_file.h>
39 #include <linux/spinlock.h>
40 #include <linux/kallsyms.h>
41 #include <linux/interrupt.h>
42 #include <linux/stacktrace.h>
43 #include <linux/debug_locks.h>
44 #include <linux/irqflags.h>
45 #include <linux/utsname.h>
46 #include <linux/hash.h>
47 #include <linux/ftrace.h>
48 #include <linux/stringify.h>
49 #include <linux/bitmap.h>
50 #include <linux/bitops.h>
51 #include <linux/gfp.h>
52 #include <linux/random.h>
53 #include <linux/jhash.h>
54 #include <linux/nmi.h>
55 #include <linux/rcupdate.h>
56 #include <linux/kprobes.h>
57 #include <linux/lockdep.h>
59 #include <asm/sections.h>
61 #include "lockdep_internals.h"
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/lock.h>
66 #ifdef CONFIG_PROVE_LOCKING
67 int prove_locking = 1;
68 module_param(prove_locking, int, 0644);
70 #define prove_locking 0
73 #ifdef CONFIG_LOCK_STAT
75 module_param(lock_stat, int, 0644);
80 DEFINE_PER_CPU(unsigned int, lockdep_recursion);
81 EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
83 static __always_inline bool lockdep_enabled(void)
88 if (this_cpu_read(lockdep_recursion))
91 if (current->lockdep_recursion)
98 * lockdep_lock: protects the lockdep graph, the hashes and the
99 * class/list/hash allocators.
101 * This is one of the rare exceptions where it's justified
102 * to use a raw spinlock - we really dont want the spinlock
103 * code to recurse back into the lockdep code...
105 static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
106 static struct task_struct *__owner;
108 static inline void lockdep_lock(void)
110 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
112 __this_cpu_inc(lockdep_recursion);
113 arch_spin_lock(&__lock);
117 static inline void lockdep_unlock(void)
119 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
121 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
125 arch_spin_unlock(&__lock);
126 __this_cpu_dec(lockdep_recursion);
129 static inline bool lockdep_assert_locked(void)
131 return DEBUG_LOCKS_WARN_ON(__owner != current);
134 static struct task_struct *lockdep_selftest_task_struct;
137 static int graph_lock(void)
141 * Make sure that if another CPU detected a bug while
142 * walking the graph we dont change it (while the other
143 * CPU is busy printing out stuff with the graph lock
153 static inline void graph_unlock(void)
159 * Turn lock debugging off and return with 0 if it was off already,
160 * and also release the graph lock:
162 static inline int debug_locks_off_graph_unlock(void)
164 int ret = debug_locks_off();
171 unsigned long nr_list_entries;
172 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
173 static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
176 * All data structures here are protected by the global debug_lock.
178 * nr_lock_classes is the number of elements of lock_classes[] that is
181 #define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
182 #define KEYHASH_SIZE (1UL << KEYHASH_BITS)
183 static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
184 unsigned long nr_lock_classes;
185 unsigned long nr_zapped_classes;
186 unsigned long max_lock_class_idx;
187 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
188 DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
190 static inline struct lock_class *hlock_class(struct held_lock *hlock)
192 unsigned int class_idx = hlock->class_idx;
194 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
197 if (!test_bit(class_idx, lock_classes_in_use)) {
199 * Someone passed in garbage, we give up.
201 DEBUG_LOCKS_WARN_ON(1);
206 * At this point, if the passed hlock->class_idx is still garbage,
207 * we just have to live with it
209 return lock_classes + class_idx;
212 #ifdef CONFIG_LOCK_STAT
213 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
215 static inline u64 lockstat_clock(void)
217 return local_clock();
220 static int lock_point(unsigned long points[], unsigned long ip)
224 for (i = 0; i < LOCKSTAT_POINTS; i++) {
225 if (points[i] == 0) {
236 static void lock_time_inc(struct lock_time *lt, u64 time)
241 if (time < lt->min || !lt->nr)
248 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
253 if (src->max > dst->max)
256 if (src->min < dst->min || !dst->nr)
259 dst->total += src->total;
263 struct lock_class_stats lock_stats(struct lock_class *class)
265 struct lock_class_stats stats;
268 memset(&stats, 0, sizeof(struct lock_class_stats));
269 for_each_possible_cpu(cpu) {
270 struct lock_class_stats *pcs =
271 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
273 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
274 stats.contention_point[i] += pcs->contention_point[i];
276 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
277 stats.contending_point[i] += pcs->contending_point[i];
279 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
280 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
282 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
283 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
285 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
286 stats.bounces[i] += pcs->bounces[i];
292 void clear_lock_stats(struct lock_class *class)
296 for_each_possible_cpu(cpu) {
297 struct lock_class_stats *cpu_stats =
298 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
300 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
302 memset(class->contention_point, 0, sizeof(class->contention_point));
303 memset(class->contending_point, 0, sizeof(class->contending_point));
306 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
308 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
311 static void lock_release_holdtime(struct held_lock *hlock)
313 struct lock_class_stats *stats;
319 holdtime = lockstat_clock() - hlock->holdtime_stamp;
321 stats = get_lock_stats(hlock_class(hlock));
323 lock_time_inc(&stats->read_holdtime, holdtime);
325 lock_time_inc(&stats->write_holdtime, holdtime);
328 static inline void lock_release_holdtime(struct held_lock *hlock)
334 * We keep a global list of all lock classes. The list is only accessed with
335 * the lockdep spinlock lock held. free_lock_classes is a list with free
336 * elements. These elements are linked together by the lock_entry member in
339 static LIST_HEAD(all_lock_classes);
340 static LIST_HEAD(free_lock_classes);
343 * struct pending_free - information about data structures about to be freed
344 * @zapped: Head of a list with struct lock_class elements.
345 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
346 * are about to be freed.
348 struct pending_free {
349 struct list_head zapped;
350 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
354 * struct delayed_free - data structures used for delayed freeing
356 * A data structure for delayed freeing of data structures that may be
357 * accessed by RCU readers at the time these were freed.
359 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
360 * @index: Index of @pf to which freed data structures are added.
361 * @scheduled: Whether or not an RCU callback has been scheduled.
362 * @pf: Array with information about data structures about to be freed.
364 static struct delayed_free {
365 struct rcu_head rcu_head;
368 struct pending_free pf[2];
372 * The lockdep classes are in a hash-table as well, for fast lookup:
374 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
375 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
376 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
377 #define classhashentry(key) (classhash_table + __classhashfn((key)))
379 static struct hlist_head classhash_table[CLASSHASH_SIZE];
382 * We put the lock dependency chains into a hash-table as well, to cache
385 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
386 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
387 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
388 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
390 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
393 * the id of held_lock
395 static inline u16 hlock_id(struct held_lock *hlock)
397 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
399 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
402 static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
404 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
408 * The hash key of the lock dependency chains is a hash itself too:
409 * it's a hash of all locks taken up to that lock, including that lock.
410 * It's a 64-bit hash, because it's important for the keys to be
413 static inline u64 iterate_chain_key(u64 key, u32 idx)
415 u32 k0 = key, k1 = key >> 32;
417 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
419 return k0 | (u64)k1 << 32;
422 void lockdep_init_task(struct task_struct *task)
424 task->lockdep_depth = 0; /* no locks held yet */
425 task->curr_chain_key = INITIAL_CHAIN_KEY;
426 task->lockdep_recursion = 0;
429 static __always_inline void lockdep_recursion_inc(void)
431 __this_cpu_inc(lockdep_recursion);
434 static __always_inline void lockdep_recursion_finish(void)
436 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
437 __this_cpu_write(lockdep_recursion, 0);
440 void lockdep_set_selftest_task(struct task_struct *task)
442 lockdep_selftest_task_struct = task;
446 * Debugging switches:
450 #define VERY_VERBOSE 0
453 # define HARDIRQ_VERBOSE 1
454 # define SOFTIRQ_VERBOSE 1
456 # define HARDIRQ_VERBOSE 0
457 # define SOFTIRQ_VERBOSE 0
460 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
462 * Quick filtering for interesting events:
464 static int class_filter(struct lock_class *class)
468 if (class->name_version == 1 &&
469 !strcmp(class->name, "lockname"))
471 if (class->name_version == 1 &&
472 !strcmp(class->name, "&struct->lockfield"))
475 /* Filter everything else. 1 would be to allow everything else */
480 static int verbose(struct lock_class *class)
483 return class_filter(class);
488 static void print_lockdep_off(const char *bug_msg)
490 printk(KERN_DEBUG "%s\n", bug_msg);
491 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
492 #ifdef CONFIG_LOCK_STAT
493 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
497 unsigned long nr_stack_trace_entries;
499 #ifdef CONFIG_PROVE_LOCKING
501 * struct lock_trace - single stack backtrace
502 * @hash_entry: Entry in a stack_trace_hash[] list.
503 * @hash: jhash() of @entries.
504 * @nr_entries: Number of entries in @entries.
505 * @entries: Actual stack backtrace.
508 struct hlist_node hash_entry;
511 unsigned long entries[] __aligned(sizeof(unsigned long));
513 #define LOCK_TRACE_SIZE_IN_LONGS \
514 (sizeof(struct lock_trace) / sizeof(unsigned long))
516 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
518 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
519 static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
521 static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
523 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
524 memcmp(t1->entries, t2->entries,
525 t1->nr_entries * sizeof(t1->entries[0])) == 0;
528 static struct lock_trace *save_trace(void)
530 struct lock_trace *trace, *t2;
531 struct hlist_head *hash_head;
535 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
536 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
538 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
539 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
540 LOCK_TRACE_SIZE_IN_LONGS;
542 if (max_entries <= 0) {
543 if (!debug_locks_off_graph_unlock())
546 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
551 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
553 hash = jhash(trace->entries, trace->nr_entries *
554 sizeof(trace->entries[0]), 0);
556 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
557 hlist_for_each_entry(t2, hash_head, hash_entry) {
558 if (traces_identical(trace, t2))
561 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
562 hlist_add_head(&trace->hash_entry, hash_head);
567 /* Return the number of stack traces in the stack_trace[] array. */
568 u64 lockdep_stack_trace_count(void)
570 struct lock_trace *trace;
574 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
575 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
583 /* Return the number of stack hash chains that have at least one stack trace. */
584 u64 lockdep_stack_hash_count(void)
589 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
590 if (!hlist_empty(&stack_trace_hash[i]))
597 unsigned int nr_hardirq_chains;
598 unsigned int nr_softirq_chains;
599 unsigned int nr_process_chains;
600 unsigned int max_lockdep_depth;
602 #ifdef CONFIG_DEBUG_LOCKDEP
604 * Various lockdep statistics:
606 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
609 #ifdef CONFIG_PROVE_LOCKING
614 #define __USAGE(__STATE) \
615 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
616 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
617 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
618 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
620 static const char *usage_str[] =
622 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
623 #include "lockdep_states.h"
625 [LOCK_USED] = "INITIAL USE",
626 [LOCK_USED_READ] = "INITIAL READ USE",
627 /* abused as string storage for verify_lock_unused() */
628 [LOCK_USAGE_STATES] = "IN-NMI",
632 const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
634 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
637 static inline unsigned long lock_flag(enum lock_usage_bit bit)
642 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
645 * The usage character defaults to '.' (i.e., irqs disabled and not in
646 * irq context), which is the safest usage category.
651 * The order of the following usage checks matters, which will
652 * result in the outcome character as follows:
654 * - '+': irq is enabled and not in irq context
655 * - '-': in irq context and irq is disabled
656 * - '?': in irq context and irq is enabled
658 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
660 if (class->usage_mask & lock_flag(bit))
662 } else if (class->usage_mask & lock_flag(bit))
668 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
672 #define LOCKDEP_STATE(__STATE) \
673 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
674 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
675 #include "lockdep_states.h"
681 static void __print_lock_name(struct lock_class *class)
683 char str[KSYM_NAME_LEN];
688 name = __get_key_name(class->key, str);
689 printk(KERN_CONT "%s", name);
691 printk(KERN_CONT "%s", name);
692 if (class->name_version > 1)
693 printk(KERN_CONT "#%d", class->name_version);
695 printk(KERN_CONT "/%d", class->subclass);
699 static void print_lock_name(struct lock_class *class)
701 char usage[LOCK_USAGE_CHARS];
703 get_usage_chars(class, usage);
705 printk(KERN_CONT " (");
706 __print_lock_name(class);
707 printk(KERN_CONT "){%s}-{%d:%d}", usage,
708 class->wait_type_outer ?: class->wait_type_inner,
709 class->wait_type_inner);
712 static void print_lockdep_cache(struct lockdep_map *lock)
715 char str[KSYM_NAME_LEN];
719 name = __get_key_name(lock->key->subkeys, str);
721 printk(KERN_CONT "%s", name);
724 static void print_lock(struct held_lock *hlock)
727 * We can be called locklessly through debug_show_all_locks() so be
728 * extra careful, the hlock might have been released and cleared.
730 * If this indeed happens, lets pretend it does not hurt to continue
731 * to print the lock unless the hlock class_idx does not point to a
732 * registered class. The rationale here is: since we don't attempt
733 * to distinguish whether we are in this situation, if it just
734 * happened we can't count on class_idx to tell either.
736 struct lock_class *lock = hlock_class(hlock);
739 printk(KERN_CONT "<RELEASED>\n");
743 printk(KERN_CONT "%px", hlock->instance);
744 print_lock_name(lock);
745 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
748 static void lockdep_print_held_locks(struct task_struct *p)
750 int i, depth = READ_ONCE(p->lockdep_depth);
753 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
755 printk("%d lock%s held by %s/%d:\n", depth,
756 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
758 * It's not reliable to print a task's held locks if it's not sleeping
759 * and it's not the current task.
761 if (p != current && task_is_running(p))
763 for (i = 0; i < depth; i++) {
765 print_lock(p->held_locks + i);
769 static void print_kernel_ident(void)
771 printk("%s %.*s %s\n", init_utsname()->release,
772 (int)strcspn(init_utsname()->version, " "),
773 init_utsname()->version,
777 static int very_verbose(struct lock_class *class)
780 return class_filter(class);
786 * Is this the address of a static object:
789 static int static_obj(const void *obj)
791 unsigned long start = (unsigned long) &_stext,
792 end = (unsigned long) &_end,
793 addr = (unsigned long) obj;
795 if (arch_is_kernel_initmem_freed(addr))
801 if ((addr >= start) && (addr < end))
804 if (arch_is_kernel_data(addr))
808 * in-kernel percpu var?
810 if (is_kernel_percpu_address(addr))
814 * module static or percpu var?
816 return is_module_address(addr) || is_module_percpu_address(addr);
821 * To make lock name printouts unique, we calculate a unique
822 * class->name_version generation counter. The caller must hold the graph
825 static int count_matching_names(struct lock_class *new_class)
827 struct lock_class *class;
830 if (!new_class->name)
833 list_for_each_entry(class, &all_lock_classes, lock_entry) {
834 if (new_class->key - new_class->subclass == class->key)
835 return class->name_version;
836 if (class->name && !strcmp(class->name, new_class->name))
837 count = max(count, class->name_version);
843 /* used from NMI context -- must be lockless */
844 static noinstr struct lock_class *
845 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
847 struct lockdep_subclass_key *key;
848 struct hlist_head *hash_head;
849 struct lock_class *class;
851 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
852 instrumentation_begin();
855 "BUG: looking up invalid subclass: %u\n", subclass);
857 "turning off the locking correctness validator.\n");
859 instrumentation_end();
864 * If it is not initialised then it has never been locked,
865 * so it won't be present in the hash table.
867 if (unlikely(!lock->key))
871 * NOTE: the class-key must be unique. For dynamic locks, a static
872 * lock_class_key variable is passed in through the mutex_init()
873 * (or spin_lock_init()) call - which acts as the key. For static
874 * locks we use the lock object itself as the key.
876 BUILD_BUG_ON(sizeof(struct lock_class_key) >
877 sizeof(struct lockdep_map));
879 key = lock->key->subkeys + subclass;
881 hash_head = classhashentry(key);
884 * We do an RCU walk of the hash, see lockdep_free_key_range().
886 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
889 hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
890 if (class->key == key) {
892 * Huh! same key, different name? Did someone trample
893 * on some memory? We're most confused.
895 WARN_ON_ONCE(class->name != lock->name &&
896 lock->key != &__lockdep_no_validate__);
905 * Static locks do not have their class-keys yet - for them the key is
906 * the lock object itself. If the lock is in the per cpu area, the
907 * canonical address of the lock (per cpu offset removed) is used.
909 static bool assign_lock_key(struct lockdep_map *lock)
911 unsigned long can_addr, addr = (unsigned long)lock;
915 * lockdep_free_key_range() assumes that struct lock_class_key
916 * objects do not overlap. Since we use the address of lock
917 * objects as class key for static objects, check whether the
918 * size of lock_class_key objects does not exceed the size of
919 * the smallest lock object.
921 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
924 if (__is_kernel_percpu_address(addr, &can_addr))
925 lock->key = (void *)can_addr;
926 else if (__is_module_percpu_address(addr, &can_addr))
927 lock->key = (void *)can_addr;
928 else if (static_obj(lock))
929 lock->key = (void *)lock;
931 /* Debug-check: all keys must be persistent! */
933 pr_err("INFO: trying to register non-static key.\n");
934 pr_err("The code is fine but needs lockdep annotation, or maybe\n");
935 pr_err("you didn't initialize this object before use?\n");
936 pr_err("turning off the locking correctness validator.\n");
944 #ifdef CONFIG_DEBUG_LOCKDEP
946 /* Check whether element @e occurs in list @h */
947 static bool in_list(struct list_head *e, struct list_head *h)
951 list_for_each(f, h) {
960 * Check whether entry @e occurs in any of the locks_after or locks_before
963 static bool in_any_class_list(struct list_head *e)
965 struct lock_class *class;
968 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
969 class = &lock_classes[i];
970 if (in_list(e, &class->locks_after) ||
971 in_list(e, &class->locks_before))
977 static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
981 list_for_each_entry(e, h, entry) {
982 if (e->links_to != c) {
983 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
985 (unsigned long)(e - list_entries),
986 e->links_to && e->links_to->name ?
987 e->links_to->name : "(?)",
988 e->class && e->class->name ? e->class->name :
996 #ifdef CONFIG_PROVE_LOCKING
997 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1000 static bool check_lock_chain_key(struct lock_chain *chain)
1002 #ifdef CONFIG_PROVE_LOCKING
1003 u64 chain_key = INITIAL_CHAIN_KEY;
1006 for (i = chain->base; i < chain->base + chain->depth; i++)
1007 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1009 * The 'unsigned long long' casts avoid that a compiler warning
1010 * is reported when building tools/lib/lockdep.
1012 if (chain->chain_key != chain_key) {
1013 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1014 (unsigned long long)(chain - lock_chains),
1015 (unsigned long long)chain->chain_key,
1016 (unsigned long long)chain_key);
1023 static bool in_any_zapped_class_list(struct lock_class *class)
1025 struct pending_free *pf;
1028 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1029 if (in_list(&class->lock_entry, &pf->zapped))
1036 static bool __check_data_structures(void)
1038 struct lock_class *class;
1039 struct lock_chain *chain;
1040 struct hlist_head *head;
1041 struct lock_list *e;
1044 /* Check whether all classes occur in a lock list. */
1045 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1046 class = &lock_classes[i];
1047 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1048 !in_list(&class->lock_entry, &free_lock_classes) &&
1049 !in_any_zapped_class_list(class)) {
1050 printk(KERN_INFO "class %px/%s is not in any class list\n",
1051 class, class->name ? : "(?)");
1056 /* Check whether all classes have valid lock lists. */
1057 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1058 class = &lock_classes[i];
1059 if (!class_lock_list_valid(class, &class->locks_before))
1061 if (!class_lock_list_valid(class, &class->locks_after))
1065 /* Check the chain_key of all lock chains. */
1066 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1067 head = chainhash_table + i;
1068 hlist_for_each_entry_rcu(chain, head, entry) {
1069 if (!check_lock_chain_key(chain))
1075 * Check whether all list entries that are in use occur in a class
1078 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1079 e = list_entries + i;
1080 if (!in_any_class_list(&e->entry)) {
1081 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1082 (unsigned int)(e - list_entries),
1083 e->class->name ? : "(?)",
1084 e->links_to->name ? : "(?)");
1090 * Check whether all list entries that are not in use do not occur in
1091 * a class lock list.
1093 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1094 e = list_entries + i;
1095 if (in_any_class_list(&e->entry)) {
1096 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1097 (unsigned int)(e - list_entries),
1098 e->class && e->class->name ? e->class->name :
1100 e->links_to && e->links_to->name ?
1101 e->links_to->name : "(?)");
1109 int check_consistency = 0;
1110 module_param(check_consistency, int, 0644);
1112 static void check_data_structures(void)
1114 static bool once = false;
1116 if (check_consistency && !once) {
1117 if (!__check_data_structures()) {
1124 #else /* CONFIG_DEBUG_LOCKDEP */
1126 static inline void check_data_structures(void) { }
1128 #endif /* CONFIG_DEBUG_LOCKDEP */
1130 static void init_chain_block_buckets(void);
1133 * Initialize the lock_classes[] array elements, the free_lock_classes list
1134 * and also the delayed_free structure.
1136 static void init_data_structures_once(void)
1138 static bool __read_mostly ds_initialized, rcu_head_initialized;
1141 if (likely(rcu_head_initialized))
1144 if (system_state >= SYSTEM_SCHEDULING) {
1145 init_rcu_head(&delayed_free.rcu_head);
1146 rcu_head_initialized = true;
1152 ds_initialized = true;
1154 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1155 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1157 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1158 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1159 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1160 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1162 init_chain_block_buckets();
1165 static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1167 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1169 return lock_keys_hash + hash;
1172 /* Register a dynamically allocated key. */
1173 void lockdep_register_key(struct lock_class_key *key)
1175 struct hlist_head *hash_head;
1176 struct lock_class_key *k;
1177 unsigned long flags;
1179 if (WARN_ON_ONCE(static_obj(key)))
1181 hash_head = keyhashentry(key);
1183 raw_local_irq_save(flags);
1186 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1187 if (WARN_ON_ONCE(k == key))
1190 hlist_add_head_rcu(&key->hash_entry, hash_head);
1194 raw_local_irq_restore(flags);
1196 EXPORT_SYMBOL_GPL(lockdep_register_key);
1198 /* Check whether a key has been registered as a dynamic key. */
1199 static bool is_dynamic_key(const struct lock_class_key *key)
1201 struct hlist_head *hash_head;
1202 struct lock_class_key *k;
1205 if (WARN_ON_ONCE(static_obj(key)))
1209 * If lock debugging is disabled lock_keys_hash[] may contain
1210 * pointers to memory that has already been freed. Avoid triggering
1211 * a use-after-free in that case by returning early.
1216 hash_head = keyhashentry(key);
1219 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1231 * Register a lock's class in the hash-table, if the class is not present
1232 * yet. Otherwise we look it up. We cache the result in the lock object
1233 * itself, so actual lookup of the hash should be once per lock object.
1235 static struct lock_class *
1236 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1238 struct lockdep_subclass_key *key;
1239 struct hlist_head *hash_head;
1240 struct lock_class *class;
1243 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1245 class = look_up_lock_class(lock, subclass);
1247 goto out_set_class_cache;
1250 if (!assign_lock_key(lock))
1252 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1256 key = lock->key->subkeys + subclass;
1257 hash_head = classhashentry(key);
1259 if (!graph_lock()) {
1263 * We have to do the hash-walk again, to avoid races
1266 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1267 if (class->key == key)
1268 goto out_unlock_set;
1271 init_data_structures_once();
1273 /* Allocate a new lock class and add it to the hash. */
1274 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1277 if (!debug_locks_off_graph_unlock()) {
1281 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1286 __set_bit(class - lock_classes, lock_classes_in_use);
1287 debug_atomic_inc(nr_unused_locks);
1289 class->name = lock->name;
1290 class->subclass = subclass;
1291 WARN_ON_ONCE(!list_empty(&class->locks_before));
1292 WARN_ON_ONCE(!list_empty(&class->locks_after));
1293 class->name_version = count_matching_names(class);
1294 class->wait_type_inner = lock->wait_type_inner;
1295 class->wait_type_outer = lock->wait_type_outer;
1296 class->lock_type = lock->lock_type;
1298 * We use RCU's safe list-add method to make
1299 * parallel walking of the hash-list safe:
1301 hlist_add_head_rcu(&class->hash_entry, hash_head);
1303 * Remove the class from the free list and add it to the global list
1306 list_move_tail(&class->lock_entry, &all_lock_classes);
1307 idx = class - lock_classes;
1308 if (idx > max_lock_class_idx)
1309 max_lock_class_idx = idx;
1311 if (verbose(class)) {
1314 printk("\nnew class %px: %s", class->key, class->name);
1315 if (class->name_version > 1)
1316 printk(KERN_CONT "#%d", class->name_version);
1317 printk(KERN_CONT "\n");
1320 if (!graph_lock()) {
1327 out_set_class_cache:
1328 if (!subclass || force)
1329 lock->class_cache[0] = class;
1330 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1331 lock->class_cache[subclass] = class;
1334 * Hash collision, did we smoke some? We found a class with a matching
1335 * hash but the subclass -- which is hashed in -- didn't match.
1337 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1343 #ifdef CONFIG_PROVE_LOCKING
1345 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1346 * with NULL on failure)
1348 static struct lock_list *alloc_list_entry(void)
1350 int idx = find_first_zero_bit(list_entries_in_use,
1351 ARRAY_SIZE(list_entries));
1353 if (idx >= ARRAY_SIZE(list_entries)) {
1354 if (!debug_locks_off_graph_unlock())
1357 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1362 __set_bit(idx, list_entries_in_use);
1363 return list_entries + idx;
1367 * Add a new dependency to the head of the list:
1369 static int add_lock_to_list(struct lock_class *this,
1370 struct lock_class *links_to, struct list_head *head,
1371 u16 distance, u8 dep,
1372 const struct lock_trace *trace)
1374 struct lock_list *entry;
1376 * Lock not present yet - get a new dependency struct and
1377 * add it to the list:
1379 entry = alloc_list_entry();
1383 entry->class = this;
1384 entry->links_to = links_to;
1386 entry->distance = distance;
1387 entry->trace = trace;
1389 * Both allocation and removal are done under the graph lock; but
1390 * iteration is under RCU-sched; see look_up_lock_class() and
1391 * lockdep_free_key_range().
1393 list_add_tail_rcu(&entry->entry, head);
1399 * For good efficiency of modular, we use power of 2
1401 #define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1402 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1405 * The circular_queue and helpers are used to implement graph
1406 * breadth-first search (BFS) algorithm, by which we can determine
1407 * whether there is a path from a lock to another. In deadlock checks,
1408 * a path from the next lock to be acquired to a previous held lock
1409 * indicates that adding the <prev> -> <next> lock dependency will
1410 * produce a circle in the graph. Breadth-first search instead of
1411 * depth-first search is used in order to find the shortest (circular)
1414 struct circular_queue {
1415 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1416 unsigned int front, rear;
1419 static struct circular_queue lock_cq;
1421 unsigned int max_bfs_queue_depth;
1423 static unsigned int lockdep_dependency_gen_id;
1425 static inline void __cq_init(struct circular_queue *cq)
1427 cq->front = cq->rear = 0;
1428 lockdep_dependency_gen_id++;
1431 static inline int __cq_empty(struct circular_queue *cq)
1433 return (cq->front == cq->rear);
1436 static inline int __cq_full(struct circular_queue *cq)
1438 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1441 static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1446 cq->element[cq->rear] = elem;
1447 cq->rear = (cq->rear + 1) & CQ_MASK;
1452 * Dequeue an element from the circular_queue, return a lock_list if
1453 * the queue is not empty, or NULL if otherwise.
1455 static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1457 struct lock_list * lock;
1462 lock = cq->element[cq->front];
1463 cq->front = (cq->front + 1) & CQ_MASK;
1468 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1470 return (cq->rear - cq->front) & CQ_MASK;
1473 static inline void mark_lock_accessed(struct lock_list *lock)
1475 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1478 static inline void visit_lock_entry(struct lock_list *lock,
1479 struct lock_list *parent)
1481 lock->parent = parent;
1484 static inline unsigned long lock_accessed(struct lock_list *lock)
1486 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1489 static inline struct lock_list *get_lock_parent(struct lock_list *child)
1491 return child->parent;
1494 static inline int get_lock_depth(struct lock_list *child)
1497 struct lock_list *parent;
1499 while ((parent = get_lock_parent(child))) {
1507 * Return the forward or backward dependency list.
1509 * @lock: the lock_list to get its class's dependency list
1510 * @offset: the offset to struct lock_class to determine whether it is
1511 * locks_after or locks_before
1513 static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1515 void *lock_class = lock->class;
1517 return lock_class + offset;
1520 * Return values of a bfs search:
1522 * BFS_E* indicates an error
1523 * BFS_R* indicates a result (match or not)
1525 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1527 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1529 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1532 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1536 BFS_EINVALIDNODE = -2,
1537 BFS_EQUEUEFULL = -1,
1543 * bfs_result < 0 means error
1545 static inline bool bfs_error(enum bfs_result res)
1551 * DEP_*_BIT in lock_list::dep
1553 * For dependency @prev -> @next:
1555 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1557 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1558 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1559 * EN: @prev is exclusive locker and @next is non-recursive locker
1561 * Note that we define the value of DEP_*_BITs so that:
1562 * bit0 is prev->read == 0
1563 * bit1 is next->read != 2
1565 #define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1566 #define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1567 #define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1568 #define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1570 #define DEP_SR_MASK (1U << (DEP_SR_BIT))
1571 #define DEP_ER_MASK (1U << (DEP_ER_BIT))
1572 #define DEP_SN_MASK (1U << (DEP_SN_BIT))
1573 #define DEP_EN_MASK (1U << (DEP_EN_BIT))
1575 static inline unsigned int
1576 __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1578 return (prev->read == 0) + ((next->read != 2) << 1);
1581 static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1583 return 1U << __calc_dep_bit(prev, next);
1587 * calculate the dep_bit for backwards edges. We care about whether @prev is
1588 * shared and whether @next is recursive.
1590 static inline unsigned int
1591 __calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1593 return (next->read != 2) + ((prev->read == 0) << 1);
1596 static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1598 return 1U << __calc_dep_bitb(prev, next);
1602 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1605 static inline void __bfs_init_root(struct lock_list *lock,
1606 struct lock_class *class)
1608 lock->class = class;
1609 lock->parent = NULL;
1614 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1615 * root for a BFS search.
1617 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1618 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1621 static inline void bfs_init_root(struct lock_list *lock,
1622 struct held_lock *hlock)
1624 __bfs_init_root(lock, hlock_class(hlock));
1625 lock->only_xr = (hlock->read == 2);
1629 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1631 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1632 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1633 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1635 static inline void bfs_init_rootb(struct lock_list *lock,
1636 struct held_lock *hlock)
1638 __bfs_init_root(lock, hlock_class(hlock));
1639 lock->only_xr = (hlock->read != 0);
1642 static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1644 if (!lock || !lock->parent)
1647 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1648 &lock->entry, struct lock_list, entry);
1652 * Breadth-First Search to find a strong path in the dependency graph.
1654 * @source_entry: the source of the path we are searching for.
1655 * @data: data used for the second parameter of @match function
1656 * @match: match function for the search
1657 * @target_entry: pointer to the target of a matched path
1658 * @offset: the offset to struct lock_class to determine whether it is
1659 * locks_after or locks_before
1661 * We may have multiple edges (considering different kinds of dependencies,
1662 * e.g. ER and SN) between two nodes in the dependency graph. But
1663 * only the strong dependency path in the graph is relevant to deadlocks. A
1664 * strong dependency path is a dependency path that doesn't have two adjacent
1665 * dependencies as -(*R)-> -(S*)->, please see:
1667 * Documentation/locking/lockdep-design.rst
1669 * for more explanation of the definition of strong dependency paths
1671 * In __bfs(), we only traverse in the strong dependency path:
1673 * In lock_list::only_xr, we record whether the previous dependency only
1674 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1675 * filter out any -(S*)-> in the current dependency and after that, the
1676 * ->only_xr is set according to whether we only have -(*R)-> left.
1678 static enum bfs_result __bfs(struct lock_list *source_entry,
1680 bool (*match)(struct lock_list *entry, void *data),
1681 bool (*skip)(struct lock_list *entry, void *data),
1682 struct lock_list **target_entry,
1685 struct circular_queue *cq = &lock_cq;
1686 struct lock_list *lock = NULL;
1687 struct lock_list *entry;
1688 struct list_head *head;
1689 unsigned int cq_depth;
1692 lockdep_assert_locked();
1695 __cq_enqueue(cq, source_entry);
1697 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1699 return BFS_EINVALIDNODE;
1702 * Step 1: check whether we already finish on this one.
1704 * If we have visited all the dependencies from this @lock to
1705 * others (iow, if we have visited all lock_list entries in
1706 * @lock->class->locks_{after,before}) we skip, otherwise go
1707 * and visit all the dependencies in the list and mark this
1710 if (lock_accessed(lock))
1713 mark_lock_accessed(lock);
1716 * Step 2: check whether prev dependency and this form a strong
1719 if (lock->parent) { /* Parent exists, check prev dependency */
1721 bool prev_only_xr = lock->parent->only_xr;
1724 * Mask out all -(S*)-> if we only have *R in previous
1725 * step, because -(*R)-> -(S*)-> don't make up a strong
1729 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1731 /* If nothing left, we skip */
1735 /* If there are only -(*R)-> left, set that for the next step */
1736 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1740 * Step 3: we haven't visited this and there is a strong
1741 * dependency path to this, so check with @match.
1742 * If @skip is provide and returns true, we skip this
1743 * lock (and any path this lock is in).
1745 if (skip && skip(lock, data))
1748 if (match(lock, data)) {
1749 *target_entry = lock;
1754 * Step 4: if not match, expand the path by adding the
1755 * forward or backwards dependencies in the search
1759 head = get_dep_list(lock, offset);
1760 list_for_each_entry_rcu(entry, head, entry) {
1761 visit_lock_entry(entry, lock);
1764 * Note we only enqueue the first of the list into the
1765 * queue, because we can always find a sibling
1766 * dependency from one (see __bfs_next()), as a result
1767 * the space of queue is saved.
1774 if (__cq_enqueue(cq, entry))
1775 return BFS_EQUEUEFULL;
1777 cq_depth = __cq_get_elem_count(cq);
1778 if (max_bfs_queue_depth < cq_depth)
1779 max_bfs_queue_depth = cq_depth;
1783 return BFS_RNOMATCH;
1786 static inline enum bfs_result
1787 __bfs_forwards(struct lock_list *src_entry,
1789 bool (*match)(struct lock_list *entry, void *data),
1790 bool (*skip)(struct lock_list *entry, void *data),
1791 struct lock_list **target_entry)
1793 return __bfs(src_entry, data, match, skip, target_entry,
1794 offsetof(struct lock_class, locks_after));
1798 static inline enum bfs_result
1799 __bfs_backwards(struct lock_list *src_entry,
1801 bool (*match)(struct lock_list *entry, void *data),
1802 bool (*skip)(struct lock_list *entry, void *data),
1803 struct lock_list **target_entry)
1805 return __bfs(src_entry, data, match, skip, target_entry,
1806 offsetof(struct lock_class, locks_before));
1810 static void print_lock_trace(const struct lock_trace *trace,
1811 unsigned int spaces)
1813 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1817 * Print a dependency chain entry (this is only done when a deadlock
1818 * has been detected):
1820 static noinline void
1821 print_circular_bug_entry(struct lock_list *target, int depth)
1823 if (debug_locks_silent)
1825 printk("\n-> #%u", depth);
1826 print_lock_name(target->class);
1827 printk(KERN_CONT ":\n");
1828 print_lock_trace(target->trace, 6);
1832 print_circular_lock_scenario(struct held_lock *src,
1833 struct held_lock *tgt,
1834 struct lock_list *prt)
1836 struct lock_class *source = hlock_class(src);
1837 struct lock_class *target = hlock_class(tgt);
1838 struct lock_class *parent = prt->class;
1841 * A direct locking problem where unsafe_class lock is taken
1842 * directly by safe_class lock, then all we need to show
1843 * is the deadlock scenario, as it is obvious that the
1844 * unsafe lock is taken under the safe lock.
1846 * But if there is a chain instead, where the safe lock takes
1847 * an intermediate lock (middle_class) where this lock is
1848 * not the same as the safe lock, then the lock chain is
1849 * used to describe the problem. Otherwise we would need
1850 * to show a different CPU case for each link in the chain
1851 * from the safe_class lock to the unsafe_class lock.
1853 if (parent != source) {
1854 printk("Chain exists of:\n ");
1855 __print_lock_name(source);
1856 printk(KERN_CONT " --> ");
1857 __print_lock_name(parent);
1858 printk(KERN_CONT " --> ");
1859 __print_lock_name(target);
1860 printk(KERN_CONT "\n\n");
1863 printk(" Possible unsafe locking scenario:\n\n");
1864 printk(" CPU0 CPU1\n");
1865 printk(" ---- ----\n");
1867 __print_lock_name(target);
1868 printk(KERN_CONT ");\n");
1870 __print_lock_name(parent);
1871 printk(KERN_CONT ");\n");
1873 __print_lock_name(target);
1874 printk(KERN_CONT ");\n");
1876 __print_lock_name(source);
1877 printk(KERN_CONT ");\n");
1878 printk("\n *** DEADLOCK ***\n\n");
1882 * When a circular dependency is detected, print the
1885 static noinline void
1886 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1887 struct held_lock *check_src,
1888 struct held_lock *check_tgt)
1890 struct task_struct *curr = current;
1892 if (debug_locks_silent)
1896 pr_warn("======================================================\n");
1897 pr_warn("WARNING: possible circular locking dependency detected\n");
1898 print_kernel_ident();
1899 pr_warn("------------------------------------------------------\n");
1900 pr_warn("%s/%d is trying to acquire lock:\n",
1901 curr->comm, task_pid_nr(curr));
1902 print_lock(check_src);
1904 pr_warn("\nbut task is already holding lock:\n");
1906 print_lock(check_tgt);
1907 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1908 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1910 print_circular_bug_entry(entry, depth);
1914 * We are about to add A -> B into the dependency graph, and in __bfs() a
1915 * strong dependency path A -> .. -> B is found: hlock_class equals
1918 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1919 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1920 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1921 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1922 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1923 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1924 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1926 * We need to make sure both the start and the end of A -> .. -> B is not
1927 * weaker than A -> B. For the start part, please see the comment in
1928 * check_redundant(). For the end part, we need:
1932 * a) A -> B is -(*R)-> (everything is not weaker than that)
1936 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1939 static inline bool hlock_equal(struct lock_list *entry, void *data)
1941 struct held_lock *hlock = (struct held_lock *)data;
1943 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1944 (hlock->read == 2 || /* A -> B is -(*R)-> */
1945 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1949 * We are about to add B -> A into the dependency graph, and in __bfs() a
1950 * strong dependency path A -> .. -> B is found: hlock_class equals
1953 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
1954 * dependency cycle, that means:
1958 * a) B -> A is -(E*)->
1962 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
1964 * as then we don't have -(*R)-> -(S*)-> in the cycle.
1966 static inline bool hlock_conflict(struct lock_list *entry, void *data)
1968 struct held_lock *hlock = (struct held_lock *)data;
1970 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1971 (hlock->read == 0 || /* B -> A is -(E*)-> */
1972 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1975 static noinline void print_circular_bug(struct lock_list *this,
1976 struct lock_list *target,
1977 struct held_lock *check_src,
1978 struct held_lock *check_tgt)
1980 struct task_struct *curr = current;
1981 struct lock_list *parent;
1982 struct lock_list *first_parent;
1985 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1988 this->trace = save_trace();
1992 depth = get_lock_depth(target);
1994 print_circular_bug_header(target, depth, check_src, check_tgt);
1996 parent = get_lock_parent(target);
1997 first_parent = parent;
2000 print_circular_bug_entry(parent, --depth);
2001 parent = get_lock_parent(parent);
2004 printk("\nother info that might help us debug this:\n\n");
2005 print_circular_lock_scenario(check_src, check_tgt,
2008 lockdep_print_held_locks(curr);
2010 printk("\nstack backtrace:\n");
2014 static noinline void print_bfs_bug(int ret)
2016 if (!debug_locks_off_graph_unlock())
2020 * Breadth-first-search failed, graph got corrupted?
2022 WARN(1, "lockdep bfs error:%d\n", ret);
2025 static bool noop_count(struct lock_list *entry, void *data)
2027 (*(unsigned long *)data)++;
2031 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2033 unsigned long count = 0;
2034 struct lock_list *target_entry;
2036 __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2040 unsigned long lockdep_count_forward_deps(struct lock_class *class)
2042 unsigned long ret, flags;
2043 struct lock_list this;
2045 __bfs_init_root(&this, class);
2047 raw_local_irq_save(flags);
2049 ret = __lockdep_count_forward_deps(&this);
2051 raw_local_irq_restore(flags);
2056 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2058 unsigned long count = 0;
2059 struct lock_list *target_entry;
2061 __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2066 unsigned long lockdep_count_backward_deps(struct lock_class *class)
2068 unsigned long ret, flags;
2069 struct lock_list this;
2071 __bfs_init_root(&this, class);
2073 raw_local_irq_save(flags);
2075 ret = __lockdep_count_backward_deps(&this);
2077 raw_local_irq_restore(flags);
2083 * Check that the dependency graph starting at <src> can lead to
2086 static noinline enum bfs_result
2087 check_path(struct held_lock *target, struct lock_list *src_entry,
2088 bool (*match)(struct lock_list *entry, void *data),
2089 bool (*skip)(struct lock_list *entry, void *data),
2090 struct lock_list **target_entry)
2092 enum bfs_result ret;
2094 ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2096 if (unlikely(bfs_error(ret)))
2103 * Prove that the dependency graph starting at <src> can not
2104 * lead to <target>. If it can, there is a circle when adding
2105 * <target> -> <src> dependency.
2107 * Print an error and return BFS_RMATCH if it does.
2109 static noinline enum bfs_result
2110 check_noncircular(struct held_lock *src, struct held_lock *target,
2111 struct lock_trace **const trace)
2113 enum bfs_result ret;
2114 struct lock_list *target_entry;
2115 struct lock_list src_entry;
2117 bfs_init_root(&src_entry, src);
2119 debug_atomic_inc(nr_cyclic_checks);
2121 ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2123 if (unlikely(ret == BFS_RMATCH)) {
2126 * If save_trace fails here, the printing might
2127 * trigger a WARN but because of the !nr_entries it
2128 * should not do bad things.
2130 *trace = save_trace();
2133 print_circular_bug(&src_entry, target_entry, src, target);
2139 #ifdef CONFIG_TRACE_IRQFLAGS
2142 * Forwards and backwards subgraph searching, for the purposes of
2143 * proving that two subgraphs can be connected by a new dependency
2144 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2146 * A irq safe->unsafe deadlock happens with the following conditions:
2148 * 1) We have a strong dependency path A -> ... -> B
2150 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2151 * irq can create a new dependency B -> A (consider the case that a holder
2152 * of B gets interrupted by an irq whose handler will try to acquire A).
2154 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2157 * For the usage bits of B:
2158 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2159 * ENABLED_IRQ usage suffices.
2160 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2161 * ENABLED_IRQ_*_READ usage suffices.
2163 * For the usage bits of A:
2164 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2165 * USED_IN_IRQ usage suffices.
2166 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2167 * USED_IN_IRQ_*_READ usage suffices.
2171 * There is a strong dependency path in the dependency graph: A -> B, and now
2172 * we need to decide which usage bit of A should be accumulated to detect
2173 * safe->unsafe bugs.
2175 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2176 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2178 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2179 * path, any usage of A should be considered. Otherwise, we should only
2180 * consider _READ usage.
2182 static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2184 if (!entry->only_xr)
2185 *(unsigned long *)mask |= entry->class->usage_mask;
2186 else /* Mask out _READ usage bits */
2187 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2193 * There is a strong dependency path in the dependency graph: A -> B, and now
2194 * we need to decide which usage bit of B conflicts with the usage bits of A,
2195 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2197 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2198 * path, any usage of B should be considered. Otherwise, we should only
2199 * consider _READ usage.
2201 static inline bool usage_match(struct lock_list *entry, void *mask)
2203 if (!entry->only_xr)
2204 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2205 else /* Mask out _READ usage bits */
2206 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2209 static inline bool usage_skip(struct lock_list *entry, void *mask)
2212 * Skip local_lock() for irq inversion detection.
2214 * For !RT, local_lock() is not a real lock, so it won't carry any
2217 * For RT, an irq inversion happens when we have lock A and B, and on
2218 * some CPU we can have:
2224 * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2226 * Now we prove local_lock() cannot exist in that dependency. First we
2227 * have the observation for any lock chain L1 -> ... -> Ln, for any
2228 * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2229 * wait context check will complain. And since B is not a sleep lock,
2230 * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2231 * local_lock() is 3, which is greater than 2, therefore there is no
2232 * way the local_lock() exists in the dependency B -> ... -> A.
2234 * As a result, we will skip local_lock(), when we search for irq
2237 if (entry->class->lock_type == LD_LOCK_PERCPU) {
2238 if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2248 * Find a node in the forwards-direction dependency sub-graph starting
2249 * at @root->class that matches @bit.
2251 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2252 * into *@target_entry.
2254 static enum bfs_result
2255 find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2256 struct lock_list **target_entry)
2258 enum bfs_result result;
2260 debug_atomic_inc(nr_find_usage_forwards_checks);
2262 result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2268 * Find a node in the backwards-direction dependency sub-graph starting
2269 * at @root->class that matches @bit.
2271 static enum bfs_result
2272 find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2273 struct lock_list **target_entry)
2275 enum bfs_result result;
2277 debug_atomic_inc(nr_find_usage_backwards_checks);
2279 result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2284 static void print_lock_class_header(struct lock_class *class, int depth)
2288 printk("%*s->", depth, "");
2289 print_lock_name(class);
2290 #ifdef CONFIG_DEBUG_LOCKDEP
2291 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2293 printk(KERN_CONT " {\n");
2295 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2296 if (class->usage_mask & (1 << bit)) {
2299 len += printk("%*s %s", depth, "", usage_str[bit]);
2300 len += printk(KERN_CONT " at:\n");
2301 print_lock_trace(class->usage_traces[bit], len);
2304 printk("%*s }\n", depth, "");
2306 printk("%*s ... key at: [<%px>] %pS\n",
2307 depth, "", class->key, class->key);
2311 * Dependency path printing:
2313 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2314 * printing out each lock in the dependency path will help on understanding how
2315 * the deadlock could happen. Here are some details about dependency path
2318 * 1) A lock_list can be either forwards or backwards for a lock dependency,
2319 * for a lock dependency A -> B, there are two lock_lists:
2321 * a) lock_list in the ->locks_after list of A, whose ->class is B and
2322 * ->links_to is A. In this case, we can say the lock_list is
2323 * "A -> B" (forwards case).
2325 * b) lock_list in the ->locks_before list of B, whose ->class is A
2326 * and ->links_to is B. In this case, we can say the lock_list is
2327 * "B <- A" (bacwards case).
2329 * The ->trace of both a) and b) point to the call trace where B was
2330 * acquired with A held.
2332 * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
2333 * represent a certain lock dependency, it only provides an initial entry
2334 * for BFS. For example, BFS may introduce a "helper" lock_list whose
2335 * ->class is A, as a result BFS will search all dependencies starting with
2336 * A, e.g. A -> B or A -> C.
2338 * The notation of a forwards helper lock_list is like "-> A", which means
2339 * we should search the forwards dependencies starting with "A", e.g A -> B
2342 * The notation of a bacwards helper lock_list is like "<- B", which means
2343 * we should search the backwards dependencies ending with "B", e.g.
2348 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2350 * We have a lock dependency path as follow:
2356 * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
2357 * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
2359 * , so it's natural that we start from @leaf and print every ->class and
2360 * ->trace until we reach the @root.
2363 print_shortest_lock_dependencies(struct lock_list *leaf,
2364 struct lock_list *root)
2366 struct lock_list *entry = leaf;
2369 /*compute depth from generated tree by BFS*/
2370 depth = get_lock_depth(leaf);
2373 print_lock_class_header(entry->class, depth);
2374 printk("%*s ... acquired at:\n", depth, "");
2375 print_lock_trace(entry->trace, 2);
2378 if (depth == 0 && (entry != root)) {
2379 printk("lockdep:%s bad path found in chain graph\n", __func__);
2383 entry = get_lock_parent(entry);
2385 } while (entry && (depth >= 0));
2389 * printk the shortest lock dependencies from @leaf to @root.
2391 * We have a lock dependency path (from a backwards search) as follow:
2397 * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
2398 * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
2400 * , so when we iterate from @leaf to @root, we actually print the lock
2401 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2403 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2404 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2405 * trace of L1 in the dependency path, which is alright, because most of the
2406 * time we can figure out where L1 is held from the call trace of L2.
2409 print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2410 struct lock_list *root)
2412 struct lock_list *entry = leaf;
2413 const struct lock_trace *trace = NULL;
2416 /*compute depth from generated tree by BFS*/
2417 depth = get_lock_depth(leaf);
2420 print_lock_class_header(entry->class, depth);
2422 printk("%*s ... acquired at:\n", depth, "");
2423 print_lock_trace(trace, 2);
2428 * Record the pointer to the trace for the next lock_list
2429 * entry, see the comments for the function.
2431 trace = entry->trace;
2433 if (depth == 0 && (entry != root)) {
2434 printk("lockdep:%s bad path found in chain graph\n", __func__);
2438 entry = get_lock_parent(entry);
2440 } while (entry && (depth >= 0));
2444 print_irq_lock_scenario(struct lock_list *safe_entry,
2445 struct lock_list *unsafe_entry,
2446 struct lock_class *prev_class,
2447 struct lock_class *next_class)
2449 struct lock_class *safe_class = safe_entry->class;
2450 struct lock_class *unsafe_class = unsafe_entry->class;
2451 struct lock_class *middle_class = prev_class;
2453 if (middle_class == safe_class)
2454 middle_class = next_class;
2457 * A direct locking problem where unsafe_class lock is taken
2458 * directly by safe_class lock, then all we need to show
2459 * is the deadlock scenario, as it is obvious that the
2460 * unsafe lock is taken under the safe lock.
2462 * But if there is a chain instead, where the safe lock takes
2463 * an intermediate lock (middle_class) where this lock is
2464 * not the same as the safe lock, then the lock chain is
2465 * used to describe the problem. Otherwise we would need
2466 * to show a different CPU case for each link in the chain
2467 * from the safe_class lock to the unsafe_class lock.
2469 if (middle_class != unsafe_class) {
2470 printk("Chain exists of:\n ");
2471 __print_lock_name(safe_class);
2472 printk(KERN_CONT " --> ");
2473 __print_lock_name(middle_class);
2474 printk(KERN_CONT " --> ");
2475 __print_lock_name(unsafe_class);
2476 printk(KERN_CONT "\n\n");
2479 printk(" Possible interrupt unsafe locking scenario:\n\n");
2480 printk(" CPU0 CPU1\n");
2481 printk(" ---- ----\n");
2483 __print_lock_name(unsafe_class);
2484 printk(KERN_CONT ");\n");
2485 printk(" local_irq_disable();\n");
2487 __print_lock_name(safe_class);
2488 printk(KERN_CONT ");\n");
2490 __print_lock_name(middle_class);
2491 printk(KERN_CONT ");\n");
2492 printk(" <Interrupt>\n");
2494 __print_lock_name(safe_class);
2495 printk(KERN_CONT ");\n");
2496 printk("\n *** DEADLOCK ***\n\n");
2500 print_bad_irq_dependency(struct task_struct *curr,
2501 struct lock_list *prev_root,
2502 struct lock_list *next_root,
2503 struct lock_list *backwards_entry,
2504 struct lock_list *forwards_entry,
2505 struct held_lock *prev,
2506 struct held_lock *next,
2507 enum lock_usage_bit bit1,
2508 enum lock_usage_bit bit2,
2509 const char *irqclass)
2511 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2515 pr_warn("=====================================================\n");
2516 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2517 irqclass, irqclass);
2518 print_kernel_ident();
2519 pr_warn("-----------------------------------------------------\n");
2520 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2521 curr->comm, task_pid_nr(curr),
2522 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2523 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2524 lockdep_hardirqs_enabled(),
2525 curr->softirqs_enabled);
2528 pr_warn("\nand this task is already holding:\n");
2530 pr_warn("which would create a new lock dependency:\n");
2531 print_lock_name(hlock_class(prev));
2533 print_lock_name(hlock_class(next));
2536 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2538 print_lock_name(backwards_entry->class);
2539 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2541 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2543 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2544 print_lock_name(forwards_entry->class);
2545 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2548 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2550 pr_warn("\nother info that might help us debug this:\n\n");
2551 print_irq_lock_scenario(backwards_entry, forwards_entry,
2552 hlock_class(prev), hlock_class(next));
2554 lockdep_print_held_locks(curr);
2556 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2557 print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2559 pr_warn("\nthe dependencies between the lock to be acquired");
2560 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2561 next_root->trace = save_trace();
2562 if (!next_root->trace)
2564 print_shortest_lock_dependencies(forwards_entry, next_root);
2566 pr_warn("\nstack backtrace:\n");
2570 static const char *state_names[] = {
2571 #define LOCKDEP_STATE(__STATE) \
2572 __stringify(__STATE),
2573 #include "lockdep_states.h"
2574 #undef LOCKDEP_STATE
2577 static const char *state_rnames[] = {
2578 #define LOCKDEP_STATE(__STATE) \
2579 __stringify(__STATE)"-READ",
2580 #include "lockdep_states.h"
2581 #undef LOCKDEP_STATE
2584 static inline const char *state_name(enum lock_usage_bit bit)
2586 if (bit & LOCK_USAGE_READ_MASK)
2587 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2589 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2593 * The bit number is encoded like:
2595 * bit0: 0 exclusive, 1 read lock
2596 * bit1: 0 used in irq, 1 irq enabled
2599 static int exclusive_bit(int new_bit)
2601 int state = new_bit & LOCK_USAGE_STATE_MASK;
2602 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2605 * keep state, bit flip the direction and strip read.
2607 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2611 * Observe that when given a bitmask where each bitnr is encoded as above, a
2612 * right shift of the mask transforms the individual bitnrs as -1 and
2613 * conversely, a left shift transforms into +1 for the individual bitnrs.
2615 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2616 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2617 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2619 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2621 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2622 * all bits set) and recompose with bitnr1 flipped.
2624 static unsigned long invert_dir_mask(unsigned long mask)
2626 unsigned long excl = 0;
2629 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2630 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2636 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2637 * usage may cause deadlock too, for example:
2641 * write_lock(l1); <irq enabled>
2647 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2648 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2651 * In fact, all of the following cases may cause deadlocks:
2653 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2654 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2655 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2656 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2658 * As a result, to calculate the "exclusive mask", first we invert the
2659 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2660 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2661 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2663 static unsigned long exclusive_mask(unsigned long mask)
2665 unsigned long excl = invert_dir_mask(mask);
2667 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2668 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2674 * Retrieve the _possible_ original mask to which @mask is
2675 * exclusive. Ie: this is the opposite of exclusive_mask().
2676 * Note that 2 possible original bits can match an exclusive
2677 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2678 * cleared. So both are returned for each exclusive bit.
2680 static unsigned long original_mask(unsigned long mask)
2682 unsigned long excl = invert_dir_mask(mask);
2684 /* Include read in existing usages */
2685 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2686 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2692 * Find the first pair of bit match between an original
2693 * usage mask and an exclusive usage mask.
2695 static int find_exclusive_match(unsigned long mask,
2696 unsigned long excl_mask,
2697 enum lock_usage_bit *bitp,
2698 enum lock_usage_bit *excl_bitp)
2700 int bit, excl, excl_read;
2702 for_each_set_bit(bit, &mask, LOCK_USED) {
2704 * exclusive_bit() strips the read bit, however,
2705 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2706 * to search excl | LOCK_USAGE_READ_MASK as well.
2708 excl = exclusive_bit(bit);
2709 excl_read = excl | LOCK_USAGE_READ_MASK;
2710 if (excl_mask & lock_flag(excl)) {
2714 } else if (excl_mask & lock_flag(excl_read)) {
2716 *excl_bitp = excl_read;
2724 * Prove that the new dependency does not connect a hardirq-safe(-read)
2725 * lock with a hardirq-unsafe lock - to achieve this we search
2726 * the backwards-subgraph starting at <prev>, and the
2727 * forwards-subgraph starting at <next>:
2729 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2730 struct held_lock *next)
2732 unsigned long usage_mask = 0, forward_mask, backward_mask;
2733 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2734 struct lock_list *target_entry1;
2735 struct lock_list *target_entry;
2736 struct lock_list this, that;
2737 enum bfs_result ret;
2740 * Step 1: gather all hard/soft IRQs usages backward in an
2741 * accumulated usage mask.
2743 bfs_init_rootb(&this, prev);
2745 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2746 if (bfs_error(ret)) {
2751 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2756 * Step 2: find exclusive uses forward that match the previous
2757 * backward accumulated mask.
2759 forward_mask = exclusive_mask(usage_mask);
2761 bfs_init_root(&that, next);
2763 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2764 if (bfs_error(ret)) {
2768 if (ret == BFS_RNOMATCH)
2772 * Step 3: we found a bad match! Now retrieve a lock from the backward
2773 * list whose usage mask matches the exclusive usage mask from the
2774 * lock found on the forward list.
2776 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2779 * When trying to add A -> B to the graph, we find that there is a
2780 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2781 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2782 * invert bits of M's usage_mask, we will find another lock N that is
2783 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2784 * cause a inversion deadlock.
2786 backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2788 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2789 if (bfs_error(ret)) {
2793 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2797 * Step 4: narrow down to a pair of incompatible usage bits
2800 ret = find_exclusive_match(target_entry->class->usage_mask,
2801 target_entry1->class->usage_mask,
2802 &backward_bit, &forward_bit);
2803 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2806 print_bad_irq_dependency(curr, &this, &that,
2807 target_entry, target_entry1,
2809 backward_bit, forward_bit,
2810 state_name(backward_bit));
2817 static inline int check_irq_usage(struct task_struct *curr,
2818 struct held_lock *prev, struct held_lock *next)
2823 static inline bool usage_skip(struct lock_list *entry, void *mask)
2828 #endif /* CONFIG_TRACE_IRQFLAGS */
2830 #ifdef CONFIG_LOCKDEP_SMALL
2832 * Check that the dependency graph starting at <src> can lead to
2833 * <target> or not. If it can, <src> -> <target> dependency is already
2836 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2837 * any error appears in the bfs search.
2839 static noinline enum bfs_result
2840 check_redundant(struct held_lock *src, struct held_lock *target)
2842 enum bfs_result ret;
2843 struct lock_list *target_entry;
2844 struct lock_list src_entry;
2846 bfs_init_root(&src_entry, src);
2848 * Special setup for check_redundant().
2850 * To report redundant, we need to find a strong dependency path that
2851 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2852 * we need to let __bfs() only search for a path starting at a -(E*)->,
2853 * we achieve this by setting the initial node's ->only_xr to true in
2854 * that case. And if <prev> is S, we set initial ->only_xr to false
2855 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2857 src_entry.only_xr = src->read == 0;
2859 debug_atomic_inc(nr_redundant_checks);
2862 * Note: we skip local_lock() for redundant check, because as the
2863 * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2866 ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2868 if (ret == BFS_RMATCH)
2869 debug_atomic_inc(nr_redundant);
2876 static inline enum bfs_result
2877 check_redundant(struct held_lock *src, struct held_lock *target)
2879 return BFS_RNOMATCH;
2884 static void inc_chains(int irq_context)
2886 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2887 nr_hardirq_chains++;
2888 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2889 nr_softirq_chains++;
2891 nr_process_chains++;
2894 static void dec_chains(int irq_context)
2896 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2897 nr_hardirq_chains--;
2898 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2899 nr_softirq_chains--;
2901 nr_process_chains--;
2905 print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2907 struct lock_class *next = hlock_class(nxt);
2908 struct lock_class *prev = hlock_class(prv);
2910 printk(" Possible unsafe locking scenario:\n\n");
2914 __print_lock_name(prev);
2915 printk(KERN_CONT ");\n");
2917 __print_lock_name(next);
2918 printk(KERN_CONT ");\n");
2919 printk("\n *** DEADLOCK ***\n\n");
2920 printk(" May be due to missing lock nesting notation\n\n");
2924 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2925 struct held_lock *next)
2927 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2931 pr_warn("============================================\n");
2932 pr_warn("WARNING: possible recursive locking detected\n");
2933 print_kernel_ident();
2934 pr_warn("--------------------------------------------\n");
2935 pr_warn("%s/%d is trying to acquire lock:\n",
2936 curr->comm, task_pid_nr(curr));
2938 pr_warn("\nbut task is already holding lock:\n");
2941 pr_warn("\nother info that might help us debug this:\n");
2942 print_deadlock_scenario(next, prev);
2943 lockdep_print_held_locks(curr);
2945 pr_warn("\nstack backtrace:\n");
2950 * Check whether we are holding such a class already.
2952 * (Note that this has to be done separately, because the graph cannot
2953 * detect such classes of deadlocks.)
2955 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
2956 * lock class is held but nest_lock is also held, i.e. we rely on the
2957 * nest_lock to avoid the deadlock.
2960 check_deadlock(struct task_struct *curr, struct held_lock *next)
2962 struct held_lock *prev;
2963 struct held_lock *nest = NULL;
2966 for (i = 0; i < curr->lockdep_depth; i++) {
2967 prev = curr->held_locks + i;
2969 if (prev->instance == next->nest_lock)
2972 if (hlock_class(prev) != hlock_class(next))
2976 * Allow read-after-read recursion of the same
2977 * lock class (i.e. read_lock(lock)+read_lock(lock)):
2979 if ((next->read == 2) && prev->read)
2983 * We're holding the nest_lock, which serializes this lock's
2984 * nesting behaviour.
2989 print_deadlock_bug(curr, prev, next);
2996 * There was a chain-cache miss, and we are about to add a new dependency
2997 * to a previous lock. We validate the following rules:
2999 * - would the adding of the <prev> -> <next> dependency create a
3000 * circular dependency in the graph? [== circular deadlock]
3002 * - does the new prev->next dependency connect any hardirq-safe lock
3003 * (in the full backwards-subgraph starting at <prev>) with any
3004 * hardirq-unsafe lock (in the full forwards-subgraph starting at
3005 * <next>)? [== illegal lock inversion with hardirq contexts]
3007 * - does the new prev->next dependency connect any softirq-safe lock
3008 * (in the full backwards-subgraph starting at <prev>) with any
3009 * softirq-unsafe lock (in the full forwards-subgraph starting at
3010 * <next>)? [== illegal lock inversion with softirq contexts]
3012 * any of these scenarios could lead to a deadlock.
3014 * Then if all the validations pass, we add the forwards and backwards
3018 check_prev_add(struct task_struct *curr, struct held_lock *prev,
3019 struct held_lock *next, u16 distance,
3020 struct lock_trace **const trace)
3022 struct lock_list *entry;
3023 enum bfs_result ret;
3025 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3027 * The warning statements below may trigger a use-after-free
3028 * of the class name. It is better to trigger a use-after free
3029 * and to have the class name most of the time instead of not
3030 * having the class name available.
3032 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3033 "Detected use-after-free of lock class %px/%s\n",
3035 hlock_class(prev)->name);
3036 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3037 "Detected use-after-free of lock class %px/%s\n",
3039 hlock_class(next)->name);
3044 * Prove that the new <prev> -> <next> dependency would not
3045 * create a circular dependency in the graph. (We do this by
3046 * a breadth-first search into the graph starting at <next>,
3047 * and check whether we can reach <prev>.)
3049 * The search is limited by the size of the circular queue (i.e.,
3050 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3051 * in the graph whose neighbours are to be checked.
3053 ret = check_noncircular(next, prev, trace);
3054 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3057 if (!check_irq_usage(curr, prev, next))
3061 * Is the <prev> -> <next> dependency already present?
3063 * (this may occur even though this is a new chain: consider
3064 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3065 * chains - the second one will be new, but L1 already has
3066 * L2 added to its dependency list, due to the first chain.)
3068 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3069 if (entry->class == hlock_class(next)) {
3071 entry->distance = 1;
3072 entry->dep |= calc_dep(prev, next);
3075 * Also, update the reverse dependency in @next's
3076 * ->locks_before list.
3078 * Here we reuse @entry as the cursor, which is fine
3079 * because we won't go to the next iteration of the
3082 * For normal cases, we return in the inner loop.
3084 * If we fail to return, we have inconsistency, i.e.
3085 * <prev>::locks_after contains <next> while
3086 * <next>::locks_before doesn't contain <prev>. In
3087 * that case, we return after the inner and indicate
3088 * something is wrong.
3090 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3091 if (entry->class == hlock_class(prev)) {
3093 entry->distance = 1;
3094 entry->dep |= calc_depb(prev, next);
3099 /* <prev> is not found in <next>::locks_before */
3105 * Is the <prev> -> <next> link redundant?
3107 ret = check_redundant(prev, next);
3110 else if (ret == BFS_RMATCH)
3114 *trace = save_trace();
3120 * Ok, all validations passed, add the new lock
3121 * to the previous lock's dependency list:
3123 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3124 &hlock_class(prev)->locks_after, distance,
3125 calc_dep(prev, next), *trace);
3130 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3131 &hlock_class(next)->locks_before, distance,
3132 calc_depb(prev, next), *trace);
3140 * Add the dependency to all directly-previous locks that are 'relevant'.
3141 * The ones that are relevant are (in increasing distance from curr):
3142 * all consecutive trylock entries and the final non-trylock entry - or
3143 * the end of this context's lock-chain - whichever comes first.
3146 check_prevs_add(struct task_struct *curr, struct held_lock *next)
3148 struct lock_trace *trace = NULL;
3149 int depth = curr->lockdep_depth;
3150 struct held_lock *hlock;
3155 * Depth must not be zero for a non-head lock:
3160 * At least two relevant locks must exist for this
3163 if (curr->held_locks[depth].irq_context !=
3164 curr->held_locks[depth-1].irq_context)
3168 u16 distance = curr->lockdep_depth - depth + 1;
3169 hlock = curr->held_locks + depth - 1;
3172 int ret = check_prev_add(curr, hlock, next, distance, &trace);
3177 * Stop after the first non-trylock entry,
3178 * as non-trylock entries have added their
3179 * own direct dependencies already, so this
3180 * lock is connected to them indirectly:
3182 if (!hlock->trylock)
3188 * End of lock-stack?
3193 * Stop the search if we cross into another context:
3195 if (curr->held_locks[depth].irq_context !=
3196 curr->held_locks[depth-1].irq_context)
3201 if (!debug_locks_off_graph_unlock())
3205 * Clearly we all shouldn't be here, but since we made it we
3206 * can reliable say we messed up our state. See the above two
3207 * gotos for reasons why we could possibly end up here.
3214 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3215 static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3216 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3217 unsigned long nr_zapped_lock_chains;
3218 unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3219 unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3220 unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3223 * The first 2 chain_hlocks entries in the chain block in the bucket
3224 * list contains the following meta data:
3227 * Bit 15 - always set to 1 (it is not a class index)
3228 * Bits 0-14 - upper 15 bits of the next block index
3229 * entry[1] - lower 16 bits of next block index
3231 * A next block index of all 1 bits means it is the end of the list.
3233 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3234 * the chain block size:
3236 * entry[2] - upper 16 bits of the chain block size
3237 * entry[3] - lower 16 bits of the chain block size
3239 #define MAX_CHAIN_BUCKETS 16
3240 #define CHAIN_BLK_FLAG (1U << 15)
3241 #define CHAIN_BLK_LIST_END 0xFFFFU
3243 static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3245 static inline int size_to_bucket(int size)
3247 if (size > MAX_CHAIN_BUCKETS)
3254 * Iterate all the chain blocks in a bucket.
3256 #define for_each_chain_block(bucket, prev, curr) \
3257 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3259 (prev) = (curr), (curr) = chain_block_next(curr))
3264 static inline int chain_block_next(int offset)
3266 int next = chain_hlocks[offset];
3268 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3270 if (next == CHAIN_BLK_LIST_END)
3273 next &= ~CHAIN_BLK_FLAG;
3275 next |= chain_hlocks[offset + 1];
3283 static inline int chain_block_size(int offset)
3285 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3288 static inline void init_chain_block(int offset, int next, int bucket, int size)
3290 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3291 chain_hlocks[offset + 1] = (u16)next;
3293 if (size && !bucket) {
3294 chain_hlocks[offset + 2] = size >> 16;
3295 chain_hlocks[offset + 3] = (u16)size;
3299 static inline void add_chain_block(int offset, int size)
3301 int bucket = size_to_bucket(size);
3302 int next = chain_block_buckets[bucket];
3305 if (unlikely(size < 2)) {
3307 * We can't store single entries on the freelist. Leak them.
3309 * One possible way out would be to uniquely mark them, other
3310 * than with CHAIN_BLK_FLAG, such that we can recover them when
3311 * the block before it is re-added.
3314 nr_lost_chain_hlocks++;
3318 nr_free_chain_hlocks += size;
3320 nr_large_chain_blocks++;
3323 * Variable sized, sort large to small.
3325 for_each_chain_block(0, prev, curr) {
3326 if (size >= chain_block_size(curr))
3329 init_chain_block(offset, curr, 0, size);
3331 chain_block_buckets[0] = offset;
3333 init_chain_block(prev, offset, 0, 0);
3337 * Fixed size, add to head.
3339 init_chain_block(offset, next, bucket, size);
3340 chain_block_buckets[bucket] = offset;
3344 * Only the first block in the list can be deleted.
3346 * For the variable size bucket[0], the first block (the largest one) is
3347 * returned, broken up and put back into the pool. So if a chain block of
3348 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3349 * queued up after the primordial chain block and never be used until the
3350 * hlock entries in the primordial chain block is almost used up. That
3351 * causes fragmentation and reduce allocation efficiency. That can be
3352 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3354 static inline void del_chain_block(int bucket, int size, int next)
3356 nr_free_chain_hlocks -= size;
3357 chain_block_buckets[bucket] = next;
3360 nr_large_chain_blocks--;
3363 static void init_chain_block_buckets(void)
3367 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3368 chain_block_buckets[i] = -1;
3370 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3374 * Return offset of a chain block of the right size or -1 if not found.
3376 * Fairly simple worst-fit allocator with the addition of a number of size
3377 * specific free lists.
3379 static int alloc_chain_hlocks(int req)
3381 int bucket, curr, size;
3384 * We rely on the MSB to act as an escape bit to denote freelist
3385 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3387 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3389 init_data_structures_once();
3391 if (nr_free_chain_hlocks < req)
3395 * We require a minimum of 2 (u16) entries to encode a freelist
3399 bucket = size_to_bucket(req);
3400 curr = chain_block_buckets[bucket];
3404 del_chain_block(bucket, req, chain_block_next(curr));
3408 curr = chain_block_buckets[0];
3412 * The variable sized freelist is sorted by size; the first entry is
3413 * the largest. Use it if it fits.
3416 size = chain_block_size(curr);
3417 if (likely(size >= req)) {
3418 del_chain_block(0, size, chain_block_next(curr));
3419 add_chain_block(curr + req, size - req);
3425 * Last resort, split a block in a larger sized bucket.
3427 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3428 bucket = size_to_bucket(size);
3429 curr = chain_block_buckets[bucket];
3433 del_chain_block(bucket, size, chain_block_next(curr));
3434 add_chain_block(curr + req, size - req);
3441 static inline void free_chain_hlocks(int base, int size)
3443 add_chain_block(base, max(size, 2));
3446 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3448 u16 chain_hlock = chain_hlocks[chain->base + i];
3449 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3451 return lock_classes + class_idx;
3455 * Returns the index of the first held_lock of the current chain
3457 static inline int get_first_held_lock(struct task_struct *curr,
3458 struct held_lock *hlock)
3461 struct held_lock *hlock_curr;
3463 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3464 hlock_curr = curr->held_locks + i;
3465 if (hlock_curr->irq_context != hlock->irq_context)
3473 #ifdef CONFIG_DEBUG_LOCKDEP
3475 * Returns the next chain_key iteration
3477 static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3479 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3481 printk(" hlock_id:%d -> chain_key:%016Lx",
3482 (unsigned int)hlock_id,
3483 (unsigned long long)new_chain_key);
3484 return new_chain_key;
3488 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3490 struct held_lock *hlock;
3491 u64 chain_key = INITIAL_CHAIN_KEY;
3492 int depth = curr->lockdep_depth;
3493 int i = get_first_held_lock(curr, hlock_next);
3495 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3496 hlock_next->irq_context);
3497 for (; i < depth; i++) {
3498 hlock = curr->held_locks + i;
3499 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3504 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3505 print_lock(hlock_next);
3508 static void print_chain_keys_chain(struct lock_chain *chain)
3511 u64 chain_key = INITIAL_CHAIN_KEY;
3514 printk("depth: %u\n", chain->depth);
3515 for (i = 0; i < chain->depth; i++) {
3516 hlock_id = chain_hlocks[chain->base + i];
3517 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3519 print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
3524 static void print_collision(struct task_struct *curr,
3525 struct held_lock *hlock_next,
3526 struct lock_chain *chain)
3529 pr_warn("============================\n");
3530 pr_warn("WARNING: chain_key collision\n");
3531 print_kernel_ident();
3532 pr_warn("----------------------------\n");
3533 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3534 pr_warn("Hash chain already cached but the contents don't match!\n");
3536 pr_warn("Held locks:");
3537 print_chain_keys_held_locks(curr, hlock_next);
3539 pr_warn("Locks in cached chain:");
3540 print_chain_keys_chain(chain);
3542 pr_warn("\nstack backtrace:\n");
3548 * Checks whether the chain and the current held locks are consistent
3549 * in depth and also in content. If they are not it most likely means
3550 * that there was a collision during the calculation of the chain_key.
3551 * Returns: 0 not passed, 1 passed
3553 static int check_no_collision(struct task_struct *curr,
3554 struct held_lock *hlock,
3555 struct lock_chain *chain)
3557 #ifdef CONFIG_DEBUG_LOCKDEP
3560 i = get_first_held_lock(curr, hlock);
3562 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3563 print_collision(curr, hlock, chain);
3567 for (j = 0; j < chain->depth - 1; j++, i++) {
3568 id = hlock_id(&curr->held_locks[i]);
3570 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3571 print_collision(curr, hlock, chain);
3580 * Given an index that is >= -1, return the index of the next lock chain.
3581 * Return -2 if there is no next lock chain.
3583 long lockdep_next_lockchain(long i)
3585 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3586 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3589 unsigned long lock_chain_count(void)
3591 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3594 /* Must be called with the graph lock held. */
3595 static struct lock_chain *alloc_lock_chain(void)
3597 int idx = find_first_zero_bit(lock_chains_in_use,
3598 ARRAY_SIZE(lock_chains));
3600 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3602 __set_bit(idx, lock_chains_in_use);
3603 return lock_chains + idx;
3607 * Adds a dependency chain into chain hashtable. And must be called with
3610 * Return 0 if fail, and graph_lock is released.
3611 * Return 1 if succeed, with graph_lock held.
3613 static inline int add_chain_cache(struct task_struct *curr,
3614 struct held_lock *hlock,
3617 struct hlist_head *hash_head = chainhashentry(chain_key);
3618 struct lock_chain *chain;
3622 * The caller must hold the graph lock, ensure we've got IRQs
3623 * disabled to make this an IRQ-safe lock.. for recursion reasons
3624 * lockdep won't complain about its own locking errors.
3626 if (lockdep_assert_locked())
3629 chain = alloc_lock_chain();
3631 if (!debug_locks_off_graph_unlock())
3634 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3638 chain->chain_key = chain_key;
3639 chain->irq_context = hlock->irq_context;
3640 i = get_first_held_lock(curr, hlock);
3641 chain->depth = curr->lockdep_depth + 1 - i;
3643 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3644 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3645 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3647 j = alloc_chain_hlocks(chain->depth);
3649 if (!debug_locks_off_graph_unlock())
3652 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3658 for (j = 0; j < chain->depth - 1; j++, i++) {
3659 int lock_id = hlock_id(curr->held_locks + i);
3661 chain_hlocks[chain->base + j] = lock_id;
3663 chain_hlocks[chain->base + j] = hlock_id(hlock);
3664 hlist_add_head_rcu(&chain->entry, hash_head);
3665 debug_atomic_inc(chain_lookup_misses);
3666 inc_chains(chain->irq_context);
3672 * Look up a dependency chain. Must be called with either the graph lock or
3673 * the RCU read lock held.
3675 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3677 struct hlist_head *hash_head = chainhashentry(chain_key);
3678 struct lock_chain *chain;
3680 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3681 if (READ_ONCE(chain->chain_key) == chain_key) {
3682 debug_atomic_inc(chain_lookup_hits);
3690 * If the key is not present yet in dependency chain cache then
3691 * add it and return 1 - in this case the new dependency chain is
3692 * validated. If the key is already hashed, return 0.
3693 * (On return with 1 graph_lock is held.)
3695 static inline int lookup_chain_cache_add(struct task_struct *curr,
3696 struct held_lock *hlock,
3699 struct lock_class *class = hlock_class(hlock);
3700 struct lock_chain *chain = lookup_chain_cache(chain_key);
3704 if (!check_no_collision(curr, hlock, chain))
3707 if (very_verbose(class)) {
3708 printk("\nhash chain already cached, key: "
3709 "%016Lx tail class: [%px] %s\n",
3710 (unsigned long long)chain_key,
3711 class->key, class->name);
3717 if (very_verbose(class)) {
3718 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3719 (unsigned long long)chain_key, class->key, class->name);
3726 * We have to walk the chain again locked - to avoid duplicates:
3728 chain = lookup_chain_cache(chain_key);
3734 if (!add_chain_cache(curr, hlock, chain_key))
3740 static int validate_chain(struct task_struct *curr,
3741 struct held_lock *hlock,
3742 int chain_head, u64 chain_key)
3745 * Trylock needs to maintain the stack of held locks, but it
3746 * does not add new dependencies, because trylock can be done
3749 * We look up the chain_key and do the O(N^2) check and update of
3750 * the dependencies only if this is a new dependency chain.
3751 * (If lookup_chain_cache_add() return with 1 it acquires
3752 * graph_lock for us)
3754 if (!hlock->trylock && hlock->check &&
3755 lookup_chain_cache_add(curr, hlock, chain_key)) {
3757 * Check whether last held lock:
3759 * - is irq-safe, if this lock is irq-unsafe
3760 * - is softirq-safe, if this lock is hardirq-unsafe
3762 * And check whether the new lock's dependency graph
3763 * could lead back to the previous lock:
3765 * - within the current held-lock stack
3766 * - across our accumulated lock dependency records
3768 * any of these scenarios could lead to a deadlock.
3771 * The simple case: does the current hold the same lock
3774 int ret = check_deadlock(curr, hlock);
3779 * Add dependency only if this lock is not the head
3780 * of the chain, and if the new lock introduces no more
3781 * lock dependency (because we already hold a lock with the
3782 * same lock class) nor deadlock (because the nest_lock
3783 * serializes nesting locks), see the comments for
3786 if (!chain_head && ret != 2) {
3787 if (!check_prevs_add(curr, hlock))
3793 /* after lookup_chain_cache_add(): */
3794 if (unlikely(!debug_locks))
3801 static inline int validate_chain(struct task_struct *curr,
3802 struct held_lock *hlock,
3803 int chain_head, u64 chain_key)
3808 static void init_chain_block_buckets(void) { }
3809 #endif /* CONFIG_PROVE_LOCKING */
3812 * We are building curr_chain_key incrementally, so double-check
3813 * it from scratch, to make sure that it's done correctly:
3815 static void check_chain_key(struct task_struct *curr)
3817 #ifdef CONFIG_DEBUG_LOCKDEP
3818 struct held_lock *hlock, *prev_hlock = NULL;
3820 u64 chain_key = INITIAL_CHAIN_KEY;
3822 for (i = 0; i < curr->lockdep_depth; i++) {
3823 hlock = curr->held_locks + i;
3824 if (chain_key != hlock->prev_chain_key) {
3827 * We got mighty confused, our chain keys don't match
3828 * with what we expect, someone trample on our task state?
3830 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3831 curr->lockdep_depth, i,
3832 (unsigned long long)chain_key,
3833 (unsigned long long)hlock->prev_chain_key);
3838 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3839 * it registered lock class index?
3841 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3844 if (prev_hlock && (prev_hlock->irq_context !=
3845 hlock->irq_context))
3846 chain_key = INITIAL_CHAIN_KEY;
3847 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3850 if (chain_key != curr->curr_chain_key) {
3853 * More smoking hash instead of calculating it, damn see these
3854 * numbers float.. I bet that a pink elephant stepped on my memory.
3856 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3857 curr->lockdep_depth, i,
3858 (unsigned long long)chain_key,
3859 (unsigned long long)curr->curr_chain_key);
3864 #ifdef CONFIG_PROVE_LOCKING
3865 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3866 enum lock_usage_bit new_bit);
3868 static void print_usage_bug_scenario(struct held_lock *lock)
3870 struct lock_class *class = hlock_class(lock);
3872 printk(" Possible unsafe locking scenario:\n\n");
3876 __print_lock_name(class);
3877 printk(KERN_CONT ");\n");
3878 printk(" <Interrupt>\n");
3880 __print_lock_name(class);
3881 printk(KERN_CONT ");\n");
3882 printk("\n *** DEADLOCK ***\n\n");
3886 print_usage_bug(struct task_struct *curr, struct held_lock *this,
3887 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3889 if (!debug_locks_off() || debug_locks_silent)
3893 pr_warn("================================\n");
3894 pr_warn("WARNING: inconsistent lock state\n");
3895 print_kernel_ident();
3896 pr_warn("--------------------------------\n");
3898 pr_warn("inconsistent {%s} -> {%s} usage.\n",
3899 usage_str[prev_bit], usage_str[new_bit]);
3901 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3902 curr->comm, task_pid_nr(curr),
3903 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
3904 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3905 lockdep_hardirqs_enabled(),
3906 lockdep_softirqs_enabled(curr));
3909 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3910 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3912 print_irqtrace_events(curr);
3913 pr_warn("\nother info that might help us debug this:\n");
3914 print_usage_bug_scenario(this);
3916 lockdep_print_held_locks(curr);
3918 pr_warn("\nstack backtrace:\n");
3923 * Print out an error if an invalid bit is set:
3926 valid_state(struct task_struct *curr, struct held_lock *this,
3927 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3929 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3931 print_usage_bug(curr, this, bad_bit, new_bit);
3939 * print irq inversion bug:
3942 print_irq_inversion_bug(struct task_struct *curr,
3943 struct lock_list *root, struct lock_list *other,
3944 struct held_lock *this, int forwards,
3945 const char *irqclass)
3947 struct lock_list *entry = other;
3948 struct lock_list *middle = NULL;
3951 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3955 pr_warn("========================================================\n");
3956 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
3957 print_kernel_ident();
3958 pr_warn("--------------------------------------------------------\n");
3959 pr_warn("%s/%d just changed the state of lock:\n",
3960 curr->comm, task_pid_nr(curr));
3963 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
3965 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
3966 print_lock_name(other->class);
3967 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
3969 pr_warn("\nother info that might help us debug this:\n");
3971 /* Find a middle lock (if one exists) */
3972 depth = get_lock_depth(other);
3974 if (depth == 0 && (entry != root)) {
3975 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
3979 entry = get_lock_parent(entry);
3981 } while (entry && entry != root && (depth >= 0));
3983 print_irq_lock_scenario(root, other,
3984 middle ? middle->class : root->class, other->class);
3986 print_irq_lock_scenario(other, root,
3987 middle ? middle->class : other->class, root->class);
3989 lockdep_print_held_locks(curr);
3991 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
3992 root->trace = save_trace();
3995 print_shortest_lock_dependencies(other, root);
3997 pr_warn("\nstack backtrace:\n");
4002 * Prove that in the forwards-direction subgraph starting at <this>
4003 * there is no lock matching <mask>:
4006 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4007 enum lock_usage_bit bit)
4009 enum bfs_result ret;
4010 struct lock_list root;
4011 struct lock_list *target_entry;
4012 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4013 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4015 bfs_init_root(&root, this);
4016 ret = find_usage_forwards(&root, usage_mask, &target_entry);
4017 if (bfs_error(ret)) {
4021 if (ret == BFS_RNOMATCH)
4024 /* Check whether write or read usage is the match */
4025 if (target_entry->class->usage_mask & lock_flag(bit)) {
4026 print_irq_inversion_bug(curr, &root, target_entry,
4027 this, 1, state_name(bit));
4029 print_irq_inversion_bug(curr, &root, target_entry,
4030 this, 1, state_name(read_bit));
4037 * Prove that in the backwards-direction subgraph starting at <this>
4038 * there is no lock matching <mask>:
4041 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4042 enum lock_usage_bit bit)
4044 enum bfs_result ret;
4045 struct lock_list root;
4046 struct lock_list *target_entry;
4047 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4048 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4050 bfs_init_rootb(&root, this);
4051 ret = find_usage_backwards(&root, usage_mask, &target_entry);
4052 if (bfs_error(ret)) {
4056 if (ret == BFS_RNOMATCH)
4059 /* Check whether write or read usage is the match */
4060 if (target_entry->class->usage_mask & lock_flag(bit)) {
4061 print_irq_inversion_bug(curr, &root, target_entry,
4062 this, 0, state_name(bit));
4064 print_irq_inversion_bug(curr, &root, target_entry,
4065 this, 0, state_name(read_bit));
4071 void print_irqtrace_events(struct task_struct *curr)
4073 const struct irqtrace_events *trace = &curr->irqtrace;
4075 printk("irq event stamp: %u\n", trace->irq_events);
4076 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
4077 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4078 (void *)trace->hardirq_enable_ip);
4079 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4080 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4081 (void *)trace->hardirq_disable_ip);
4082 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
4083 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4084 (void *)trace->softirq_enable_ip);
4085 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4086 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4087 (void *)trace->softirq_disable_ip);
4090 static int HARDIRQ_verbose(struct lock_class *class)
4093 return class_filter(class);
4098 static int SOFTIRQ_verbose(struct lock_class *class)
4101 return class_filter(class);
4106 static int (*state_verbose_f[])(struct lock_class *class) = {
4107 #define LOCKDEP_STATE(__STATE) \
4109 #include "lockdep_states.h"
4110 #undef LOCKDEP_STATE
4113 static inline int state_verbose(enum lock_usage_bit bit,
4114 struct lock_class *class)
4116 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4119 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4120 enum lock_usage_bit bit, const char *name);
4123 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4124 enum lock_usage_bit new_bit)
4126 int excl_bit = exclusive_bit(new_bit);
4127 int read = new_bit & LOCK_USAGE_READ_MASK;
4128 int dir = new_bit & LOCK_USAGE_DIR_MASK;
4131 * Validate that this particular lock does not have conflicting
4134 if (!valid_state(curr, this, new_bit, excl_bit))
4138 * Check for read in write conflicts
4140 if (!read && !valid_state(curr, this, new_bit,
4141 excl_bit + LOCK_USAGE_READ_MASK))
4146 * Validate that the lock dependencies don't have conflicting usage
4151 * mark ENABLED has to look backwards -- to ensure no dependee
4152 * has USED_IN state, which, again, would allow recursion deadlocks.
4154 if (!check_usage_backwards(curr, this, excl_bit))
4158 * mark USED_IN has to look forwards -- to ensure no dependency
4159 * has ENABLED state, which would allow recursion deadlocks.
4161 if (!check_usage_forwards(curr, this, excl_bit))
4165 if (state_verbose(new_bit, hlock_class(this)))
4172 * Mark all held locks with a usage bit:
4175 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4177 struct held_lock *hlock;
4180 for (i = 0; i < curr->lockdep_depth; i++) {
4181 enum lock_usage_bit hlock_bit = base_bit;
4182 hlock = curr->held_locks + i;
4185 hlock_bit += LOCK_USAGE_READ_MASK;
4187 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4192 if (!mark_lock(curr, hlock, hlock_bit))
4200 * Hardirqs will be enabled:
4202 static void __trace_hardirqs_on_caller(void)
4204 struct task_struct *curr = current;
4207 * We are going to turn hardirqs on, so set the
4208 * usage bit for all held locks:
4210 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4213 * If we have softirqs enabled, then set the usage
4214 * bit for all held locks. (disabled hardirqs prevented
4215 * this bit from being set before)
4217 if (curr->softirqs_enabled)
4218 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4222 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4224 * Invoked before a possible transition to RCU idle from exit to user or
4225 * guest mode. This ensures that all RCU operations are done before RCU
4226 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4227 * invoked to set the final state.
4229 void lockdep_hardirqs_on_prepare(void)
4231 if (unlikely(!debug_locks))
4235 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4237 if (unlikely(in_nmi()))
4240 if (unlikely(this_cpu_read(lockdep_recursion)))
4243 if (unlikely(lockdep_hardirqs_enabled())) {
4245 * Neither irq nor preemption are disabled here
4246 * so this is racy by nature but losing one hit
4247 * in a stat is not a big deal.
4249 __debug_atomic_inc(redundant_hardirqs_on);
4254 * We're enabling irqs and according to our state above irqs weren't
4255 * already enabled, yet we find the hardware thinks they are in fact
4256 * enabled.. someone messed up their IRQ state tracing.
4258 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4262 * See the fine text that goes along with this variable definition.
4264 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4268 * Can't allow enabling interrupts while in an interrupt handler,
4269 * that's general bad form and such. Recursion, limited stack etc..
4271 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4274 current->hardirq_chain_key = current->curr_chain_key;
4276 lockdep_recursion_inc();
4277 __trace_hardirqs_on_caller();
4278 lockdep_recursion_finish();
4280 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4282 void noinstr lockdep_hardirqs_on(unsigned long ip)
4284 struct irqtrace_events *trace = ¤t->irqtrace;
4286 if (unlikely(!debug_locks))
4290 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4291 * tracking state and hardware state are out of sync.
4293 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4294 * and not rely on hardware state like normal interrupts.
4296 if (unlikely(in_nmi())) {
4297 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4302 * - recursion check, because NMI can hit lockdep;
4303 * - hardware state check, because above;
4304 * - chain_key check, see lockdep_hardirqs_on_prepare().
4309 if (unlikely(this_cpu_read(lockdep_recursion)))
4312 if (lockdep_hardirqs_enabled()) {
4314 * Neither irq nor preemption are disabled here
4315 * so this is racy by nature but losing one hit
4316 * in a stat is not a big deal.
4318 __debug_atomic_inc(redundant_hardirqs_on);
4323 * We're enabling irqs and according to our state above irqs weren't
4324 * already enabled, yet we find the hardware thinks they are in fact
4325 * enabled.. someone messed up their IRQ state tracing.
4327 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4331 * Ensure the lock stack remained unchanged between
4332 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4334 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4335 current->curr_chain_key);
4338 /* we'll do an OFF -> ON transition: */
4339 __this_cpu_write(hardirqs_enabled, 1);
4340 trace->hardirq_enable_ip = ip;
4341 trace->hardirq_enable_event = ++trace->irq_events;
4342 debug_atomic_inc(hardirqs_on_events);
4344 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4347 * Hardirqs were disabled:
4349 void noinstr lockdep_hardirqs_off(unsigned long ip)
4351 if (unlikely(!debug_locks))
4355 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4356 * they will restore the software state. This ensures the software
4357 * state is consistent inside NMIs as well.
4360 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4362 } else if (__this_cpu_read(lockdep_recursion))
4366 * So we're supposed to get called after you mask local IRQs, but for
4367 * some reason the hardware doesn't quite think you did a proper job.
4369 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4372 if (lockdep_hardirqs_enabled()) {
4373 struct irqtrace_events *trace = ¤t->irqtrace;
4376 * We have done an ON -> OFF transition:
4378 __this_cpu_write(hardirqs_enabled, 0);
4379 trace->hardirq_disable_ip = ip;
4380 trace->hardirq_disable_event = ++trace->irq_events;
4381 debug_atomic_inc(hardirqs_off_events);
4383 debug_atomic_inc(redundant_hardirqs_off);
4386 EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4389 * Softirqs will be enabled:
4391 void lockdep_softirqs_on(unsigned long ip)
4393 struct irqtrace_events *trace = ¤t->irqtrace;
4395 if (unlikely(!lockdep_enabled()))
4399 * We fancy IRQs being disabled here, see softirq.c, avoids
4400 * funny state and nesting things.
4402 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4405 if (current->softirqs_enabled) {
4406 debug_atomic_inc(redundant_softirqs_on);
4410 lockdep_recursion_inc();
4412 * We'll do an OFF -> ON transition:
4414 current->softirqs_enabled = 1;
4415 trace->softirq_enable_ip = ip;
4416 trace->softirq_enable_event = ++trace->irq_events;
4417 debug_atomic_inc(softirqs_on_events);
4419 * We are going to turn softirqs on, so set the
4420 * usage bit for all held locks, if hardirqs are
4423 if (lockdep_hardirqs_enabled())
4424 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4425 lockdep_recursion_finish();
4429 * Softirqs were disabled:
4431 void lockdep_softirqs_off(unsigned long ip)
4433 if (unlikely(!lockdep_enabled()))
4437 * We fancy IRQs being disabled here, see softirq.c
4439 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4442 if (current->softirqs_enabled) {
4443 struct irqtrace_events *trace = ¤t->irqtrace;
4446 * We have done an ON -> OFF transition:
4448 current->softirqs_enabled = 0;
4449 trace->softirq_disable_ip = ip;
4450 trace->softirq_disable_event = ++trace->irq_events;
4451 debug_atomic_inc(softirqs_off_events);
4453 * Whoops, we wanted softirqs off, so why aren't they?
4455 DEBUG_LOCKS_WARN_ON(!softirq_count());
4457 debug_atomic_inc(redundant_softirqs_off);
4461 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4467 * If non-trylock use in a hardirq or softirq context, then
4468 * mark the lock as used in these contexts:
4470 if (!hlock->trylock) {
4472 if (lockdep_hardirq_context())
4473 if (!mark_lock(curr, hlock,
4474 LOCK_USED_IN_HARDIRQ_READ))
4476 if (curr->softirq_context)
4477 if (!mark_lock(curr, hlock,
4478 LOCK_USED_IN_SOFTIRQ_READ))
4481 if (lockdep_hardirq_context())
4482 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4484 if (curr->softirq_context)
4485 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4489 if (!hlock->hardirqs_off) {
4491 if (!mark_lock(curr, hlock,
4492 LOCK_ENABLED_HARDIRQ_READ))
4494 if (curr->softirqs_enabled)
4495 if (!mark_lock(curr, hlock,
4496 LOCK_ENABLED_SOFTIRQ_READ))
4499 if (!mark_lock(curr, hlock,
4500 LOCK_ENABLED_HARDIRQ))
4502 if (curr->softirqs_enabled)
4503 if (!mark_lock(curr, hlock,
4504 LOCK_ENABLED_SOFTIRQ))
4510 /* mark it as used: */
4511 if (!mark_lock(curr, hlock, LOCK_USED))
4517 static inline unsigned int task_irq_context(struct task_struct *task)
4519 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4520 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4523 static int separate_irq_context(struct task_struct *curr,
4524 struct held_lock *hlock)
4526 unsigned int depth = curr->lockdep_depth;
4529 * Keep track of points where we cross into an interrupt context:
4532 struct held_lock *prev_hlock;
4534 prev_hlock = curr->held_locks + depth-1;
4536 * If we cross into another context, reset the
4537 * hash key (this also prevents the checking and the
4538 * adding of the dependency to 'prev'):
4540 if (prev_hlock->irq_context != hlock->irq_context)
4547 * Mark a lock with a usage bit, and validate the state transition:
4549 static int mark_lock(struct task_struct *curr, struct held_lock *this,
4550 enum lock_usage_bit new_bit)
4552 unsigned int new_mask, ret = 1;
4554 if (new_bit >= LOCK_USAGE_STATES) {
4555 DEBUG_LOCKS_WARN_ON(1);
4559 if (new_bit == LOCK_USED && this->read)
4560 new_bit = LOCK_USED_READ;
4562 new_mask = 1 << new_bit;
4565 * If already set then do not dirty the cacheline,
4566 * nor do any checks:
4568 if (likely(hlock_class(this)->usage_mask & new_mask))
4574 * Make sure we didn't race:
4576 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4579 if (!hlock_class(this)->usage_mask)
4580 debug_atomic_dec(nr_unused_locks);
4582 hlock_class(this)->usage_mask |= new_mask;
4584 if (new_bit < LOCK_TRACE_STATES) {
4585 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4589 if (new_bit < LOCK_USED) {
4590 ret = mark_lock_irq(curr, this, new_bit);
4599 * We must printk outside of the graph_lock:
4602 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4604 print_irqtrace_events(curr);
4611 static inline short task_wait_context(struct task_struct *curr)
4614 * Set appropriate wait type for the context; for IRQs we have to take
4615 * into account force_irqthread as that is implied by PREEMPT_RT.
4617 if (lockdep_hardirq_context()) {
4619 * Check if force_irqthreads will run us threaded.
4621 if (curr->hardirq_threaded || curr->irq_config)
4622 return LD_WAIT_CONFIG;
4624 return LD_WAIT_SPIN;
4625 } else if (curr->softirq_context) {
4627 * Softirqs are always threaded.
4629 return LD_WAIT_CONFIG;
4636 print_lock_invalid_wait_context(struct task_struct *curr,
4637 struct held_lock *hlock)
4641 if (!debug_locks_off())
4643 if (debug_locks_silent)
4647 pr_warn("=============================\n");
4648 pr_warn("[ BUG: Invalid wait context ]\n");
4649 print_kernel_ident();
4650 pr_warn("-----------------------------\n");
4652 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4655 pr_warn("other info that might help us debug this:\n");
4657 curr_inner = task_wait_context(curr);
4658 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4660 lockdep_print_held_locks(curr);
4662 pr_warn("stack backtrace:\n");
4669 * Verify the wait_type context.
4671 * This check validates we takes locks in the right wait-type order; that is it
4672 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4673 * acquire spinlocks inside raw_spinlocks and the sort.
4675 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4676 * can be taken from (pretty much) any context but also has constraints.
4677 * However when taken in a stricter environment the RCU lock does not loosen
4680 * Therefore we must look for the strictest environment in the lock stack and
4681 * compare that to the lock we're trying to acquire.
4683 static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4685 u8 next_inner = hlock_class(next)->wait_type_inner;
4686 u8 next_outer = hlock_class(next)->wait_type_outer;
4690 if (!next_inner || next->trylock)
4694 next_outer = next_inner;
4697 * Find start of current irq_context..
4699 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4700 struct held_lock *prev = curr->held_locks + depth;
4701 if (prev->irq_context != next->irq_context)
4706 curr_inner = task_wait_context(curr);
4708 for (; depth < curr->lockdep_depth; depth++) {
4709 struct held_lock *prev = curr->held_locks + depth;
4710 u8 prev_inner = hlock_class(prev)->wait_type_inner;
4714 * We can have a bigger inner than a previous one
4715 * when outer is smaller than inner, as with RCU.
4717 * Also due to trylocks.
4719 curr_inner = min(curr_inner, prev_inner);
4723 if (next_outer > curr_inner)
4724 return print_lock_invalid_wait_context(curr, next);
4729 #else /* CONFIG_PROVE_LOCKING */
4732 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4737 static inline unsigned int task_irq_context(struct task_struct *task)
4742 static inline int separate_irq_context(struct task_struct *curr,
4743 struct held_lock *hlock)
4748 static inline int check_wait_context(struct task_struct *curr,
4749 struct held_lock *next)
4754 #endif /* CONFIG_PROVE_LOCKING */
4757 * Initialize a lock instance's lock-class mapping info:
4759 void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4760 struct lock_class_key *key, int subclass,
4761 u8 inner, u8 outer, u8 lock_type)
4765 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4766 lock->class_cache[i] = NULL;
4768 #ifdef CONFIG_LOCK_STAT
4769 lock->cpu = raw_smp_processor_id();
4773 * Can't be having no nameless bastards around this place!
4775 if (DEBUG_LOCKS_WARN_ON(!name)) {
4776 lock->name = "NULL";
4782 lock->wait_type_outer = outer;
4783 lock->wait_type_inner = inner;
4784 lock->lock_type = lock_type;
4787 * No key, no joy, we need to hash something.
4789 if (DEBUG_LOCKS_WARN_ON(!key))
4792 * Sanity check, the lock-class key must either have been allocated
4793 * statically or must have been registered as a dynamic key.
4795 if (!static_obj(key) && !is_dynamic_key(key)) {
4797 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4798 DEBUG_LOCKS_WARN_ON(1);
4803 if (unlikely(!debug_locks))
4807 unsigned long flags;
4809 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4812 raw_local_irq_save(flags);
4813 lockdep_recursion_inc();
4814 register_lock_class(lock, subclass, 1);
4815 lockdep_recursion_finish();
4816 raw_local_irq_restore(flags);
4819 EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4821 struct lock_class_key __lockdep_no_validate__;
4822 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4825 print_lock_nested_lock_not_held(struct task_struct *curr,
4826 struct held_lock *hlock)
4828 if (!debug_locks_off())
4830 if (debug_locks_silent)
4834 pr_warn("==================================\n");
4835 pr_warn("WARNING: Nested lock was not taken\n");
4836 print_kernel_ident();
4837 pr_warn("----------------------------------\n");
4839 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4842 pr_warn("\nbut this task is not holding:\n");
4843 pr_warn("%s\n", hlock->nest_lock->name);
4845 pr_warn("\nstack backtrace:\n");
4848 pr_warn("\nother info that might help us debug this:\n");
4849 lockdep_print_held_locks(curr);
4851 pr_warn("\nstack backtrace:\n");
4855 static int __lock_is_held(const struct lockdep_map *lock, int read);
4858 * This gets called for every mutex_lock*()/spin_lock*() operation.
4859 * We maintain the dependency maps and validate the locking attempt:
4861 * The callers must make sure that IRQs are disabled before calling it,
4862 * otherwise we could get an interrupt which would want to take locks,
4863 * which would end up in lockdep again.
4865 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
4866 int trylock, int read, int check, int hardirqs_off,
4867 struct lockdep_map *nest_lock, unsigned long ip,
4868 int references, int pin_count)
4870 struct task_struct *curr = current;
4871 struct lock_class *class = NULL;
4872 struct held_lock *hlock;
4878 if (unlikely(!debug_locks))
4881 if (!prove_locking || lock->key == &__lockdep_no_validate__)
4884 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
4885 class = lock->class_cache[subclass];
4889 if (unlikely(!class)) {
4890 class = register_lock_class(lock, subclass, 0);
4895 debug_class_ops_inc(class);
4897 if (very_verbose(class)) {
4898 printk("\nacquire class [%px] %s", class->key, class->name);
4899 if (class->name_version > 1)
4900 printk(KERN_CONT "#%d", class->name_version);
4901 printk(KERN_CONT "\n");
4906 * Add the lock to the list of currently held locks.
4907 * (we dont increase the depth just yet, up until the
4908 * dependency checks are done)
4910 depth = curr->lockdep_depth;
4912 * Ran out of static storage for our per-task lock stack again have we?
4914 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
4917 class_idx = class - lock_classes;
4919 if (depth) { /* we're holding locks */
4920 hlock = curr->held_locks + depth - 1;
4921 if (hlock->class_idx == class_idx && nest_lock) {
4925 if (!hlock->references)
4926 hlock->references++;
4928 hlock->references += references;
4931 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
4938 hlock = curr->held_locks + depth;
4940 * Plain impossible, we just registered it and checked it weren't no
4941 * NULL like.. I bet this mushroom I ate was good!
4943 if (DEBUG_LOCKS_WARN_ON(!class))
4945 hlock->class_idx = class_idx;
4946 hlock->acquire_ip = ip;
4947 hlock->instance = lock;
4948 hlock->nest_lock = nest_lock;
4949 hlock->irq_context = task_irq_context(curr);
4950 hlock->trylock = trylock;
4952 hlock->check = check;
4953 hlock->hardirqs_off = !!hardirqs_off;
4954 hlock->references = references;
4955 #ifdef CONFIG_LOCK_STAT
4956 hlock->waittime_stamp = 0;
4957 hlock->holdtime_stamp = lockstat_clock();
4959 hlock->pin_count = pin_count;
4961 if (check_wait_context(curr, hlock))
4964 /* Initialize the lock usage bit */
4965 if (!mark_usage(curr, hlock, check))
4969 * Calculate the chain hash: it's the combined hash of all the
4970 * lock keys along the dependency chain. We save the hash value
4971 * at every step so that we can get the current hash easily
4972 * after unlock. The chain hash is then used to cache dependency
4975 * The 'key ID' is what is the most compact key value to drive
4976 * the hash, not class->key.
4979 * Whoops, we did it again.. class_idx is invalid.
4981 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
4984 chain_key = curr->curr_chain_key;
4987 * How can we have a chain hash when we ain't got no keys?!
4989 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
4994 hlock->prev_chain_key = chain_key;
4995 if (separate_irq_context(curr, hlock)) {
4996 chain_key = INITIAL_CHAIN_KEY;
4999 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
5001 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
5002 print_lock_nested_lock_not_held(curr, hlock);
5006 if (!debug_locks_silent) {
5007 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
5008 WARN_ON_ONCE(!hlock_class(hlock)->key);
5011 if (!validate_chain(curr, hlock, chain_head, chain_key))
5014 curr->curr_chain_key = chain_key;
5015 curr->lockdep_depth++;
5016 check_chain_key(curr);
5017 #ifdef CONFIG_DEBUG_LOCKDEP
5018 if (unlikely(!debug_locks))
5021 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
5023 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
5024 printk(KERN_DEBUG "depth: %i max: %lu!\n",
5025 curr->lockdep_depth, MAX_LOCK_DEPTH);
5027 lockdep_print_held_locks(current);
5028 debug_show_all_locks();
5034 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
5035 max_lockdep_depth = curr->lockdep_depth;
5040 static void print_unlock_imbalance_bug(struct task_struct *curr,
5041 struct lockdep_map *lock,
5044 if (!debug_locks_off())
5046 if (debug_locks_silent)
5050 pr_warn("=====================================\n");
5051 pr_warn("WARNING: bad unlock balance detected!\n");
5052 print_kernel_ident();
5053 pr_warn("-------------------------------------\n");
5054 pr_warn("%s/%d is trying to release lock (",
5055 curr->comm, task_pid_nr(curr));
5056 print_lockdep_cache(lock);
5058 print_ip_sym(KERN_WARNING, ip);
5059 pr_warn("but there are no more locks to release!\n");
5060 pr_warn("\nother info that might help us debug this:\n");
5061 lockdep_print_held_locks(curr);
5063 pr_warn("\nstack backtrace:\n");
5067 static noinstr int match_held_lock(const struct held_lock *hlock,
5068 const struct lockdep_map *lock)
5070 if (hlock->instance == lock)
5073 if (hlock->references) {
5074 const struct lock_class *class = lock->class_cache[0];
5077 class = look_up_lock_class(lock, 0);
5080 * If look_up_lock_class() failed to find a class, we're trying
5081 * to test if we hold a lock that has never yet been acquired.
5082 * Clearly if the lock hasn't been acquired _ever_, we're not
5083 * holding it either, so report failure.
5089 * References, but not a lock we're actually ref-counting?
5090 * State got messed up, follow the sites that change ->references
5091 * and try to make sense of it.
5093 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
5096 if (hlock->class_idx == class - lock_classes)
5103 /* @depth must not be zero */
5104 static struct held_lock *find_held_lock(struct task_struct *curr,
5105 struct lockdep_map *lock,
5106 unsigned int depth, int *idx)
5108 struct held_lock *ret, *hlock, *prev_hlock;
5112 hlock = curr->held_locks + i;
5114 if (match_held_lock(hlock, lock))
5118 for (i--, prev_hlock = hlock--;
5120 i--, prev_hlock = hlock--) {
5122 * We must not cross into another context:
5124 if (prev_hlock->irq_context != hlock->irq_context) {
5128 if (match_held_lock(hlock, lock)) {
5139 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
5140 int idx, unsigned int *merged)
5142 struct held_lock *hlock;
5143 int first_idx = idx;
5145 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
5148 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
5149 switch (__lock_acquire(hlock->instance,
5150 hlock_class(hlock)->subclass,
5152 hlock->read, hlock->check,
5153 hlock->hardirqs_off,
5154 hlock->nest_lock, hlock->acquire_ip,
5155 hlock->references, hlock->pin_count)) {
5161 *merged += (idx == first_idx);
5172 __lock_set_class(struct lockdep_map *lock, const char *name,
5173 struct lock_class_key *key, unsigned int subclass,
5176 struct task_struct *curr = current;
5177 unsigned int depth, merged = 0;
5178 struct held_lock *hlock;
5179 struct lock_class *class;
5182 if (unlikely(!debug_locks))
5185 depth = curr->lockdep_depth;
5187 * This function is about (re)setting the class of a held lock,
5188 * yet we're not actually holding any locks. Naughty user!
5190 if (DEBUG_LOCKS_WARN_ON(!depth))
5193 hlock = find_held_lock(curr, lock, depth, &i);
5195 print_unlock_imbalance_bug(curr, lock, ip);
5199 lockdep_init_map_type(lock, name, key, 0,
5200 lock->wait_type_inner,
5201 lock->wait_type_outer,
5203 class = register_lock_class(lock, subclass, 0);
5204 hlock->class_idx = class - lock_classes;
5206 curr->lockdep_depth = i;
5207 curr->curr_chain_key = hlock->prev_chain_key;
5209 if (reacquire_held_locks(curr, depth, i, &merged))
5213 * I took it apart and put it back together again, except now I have
5214 * these 'spare' parts.. where shall I put them.
5216 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5221 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5223 struct task_struct *curr = current;
5224 unsigned int depth, merged = 0;
5225 struct held_lock *hlock;
5228 if (unlikely(!debug_locks))
5231 depth = curr->lockdep_depth;
5233 * This function is about (re)setting the class of a held lock,
5234 * yet we're not actually holding any locks. Naughty user!
5236 if (DEBUG_LOCKS_WARN_ON(!depth))
5239 hlock = find_held_lock(curr, lock, depth, &i);
5241 print_unlock_imbalance_bug(curr, lock, ip);
5245 curr->lockdep_depth = i;
5246 curr->curr_chain_key = hlock->prev_chain_key;
5248 WARN(hlock->read, "downgrading a read lock");
5250 hlock->acquire_ip = ip;
5252 if (reacquire_held_locks(curr, depth, i, &merged))
5255 /* Merging can't happen with unchanged classes.. */
5256 if (DEBUG_LOCKS_WARN_ON(merged))
5260 * I took it apart and put it back together again, except now I have
5261 * these 'spare' parts.. where shall I put them.
5263 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5270 * Remove the lock from the list of currently held locks - this gets
5271 * called on mutex_unlock()/spin_unlock*() (or on a failed
5272 * mutex_lock_interruptible()).
5275 __lock_release(struct lockdep_map *lock, unsigned long ip)
5277 struct task_struct *curr = current;
5278 unsigned int depth, merged = 1;
5279 struct held_lock *hlock;
5282 if (unlikely(!debug_locks))
5285 depth = curr->lockdep_depth;
5287 * So we're all set to release this lock.. wait what lock? We don't
5288 * own any locks, you've been drinking again?
5291 print_unlock_imbalance_bug(curr, lock, ip);
5296 * Check whether the lock exists in the current stack
5299 hlock = find_held_lock(curr, lock, depth, &i);
5301 print_unlock_imbalance_bug(curr, lock, ip);
5305 if (hlock->instance == lock)
5306 lock_release_holdtime(hlock);
5308 WARN(hlock->pin_count, "releasing a pinned lock\n");
5310 if (hlock->references) {
5311 hlock->references--;
5312 if (hlock->references) {
5314 * We had, and after removing one, still have
5315 * references, the current lock stack is still
5316 * valid. We're done!
5323 * We have the right lock to unlock, 'hlock' points to it.
5324 * Now we remove it from the stack, and add back the other
5325 * entries (if any), recalculating the hash along the way:
5328 curr->lockdep_depth = i;
5329 curr->curr_chain_key = hlock->prev_chain_key;
5332 * The most likely case is when the unlock is on the innermost
5333 * lock. In this case, we are done!
5338 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5342 * We had N bottles of beer on the wall, we drank one, but now
5343 * there's not N-1 bottles of beer left on the wall...
5344 * Pouring two of the bottles together is acceptable.
5346 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5349 * Since reacquire_held_locks() would have called check_chain_key()
5350 * indirectly via __lock_acquire(), we don't need to do it again
5356 static __always_inline
5357 int __lock_is_held(const struct lockdep_map *lock, int read)
5359 struct task_struct *curr = current;
5362 for (i = 0; i < curr->lockdep_depth; i++) {
5363 struct held_lock *hlock = curr->held_locks + i;
5365 if (match_held_lock(hlock, lock)) {
5366 if (read == -1 || !!hlock->read == read)
5367 return LOCK_STATE_HELD;
5369 return LOCK_STATE_NOT_HELD;
5373 return LOCK_STATE_NOT_HELD;
5376 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5378 struct pin_cookie cookie = NIL_COOKIE;
5379 struct task_struct *curr = current;
5382 if (unlikely(!debug_locks))
5385 for (i = 0; i < curr->lockdep_depth; i++) {
5386 struct held_lock *hlock = curr->held_locks + i;
5388 if (match_held_lock(hlock, lock)) {
5390 * Grab 16bits of randomness; this is sufficient to not
5391 * be guessable and still allows some pin nesting in
5392 * our u32 pin_count.
5394 cookie.val = 1 + (prandom_u32() >> 16);
5395 hlock->pin_count += cookie.val;
5400 WARN(1, "pinning an unheld lock\n");
5404 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5406 struct task_struct *curr = current;
5409 if (unlikely(!debug_locks))
5412 for (i = 0; i < curr->lockdep_depth; i++) {
5413 struct held_lock *hlock = curr->held_locks + i;
5415 if (match_held_lock(hlock, lock)) {
5416 hlock->pin_count += cookie.val;
5421 WARN(1, "pinning an unheld lock\n");
5424 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5426 struct task_struct *curr = current;
5429 if (unlikely(!debug_locks))
5432 for (i = 0; i < curr->lockdep_depth; i++) {
5433 struct held_lock *hlock = curr->held_locks + i;
5435 if (match_held_lock(hlock, lock)) {
5436 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5439 hlock->pin_count -= cookie.val;
5441 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5442 hlock->pin_count = 0;
5448 WARN(1, "unpinning an unheld lock\n");
5452 * Check whether we follow the irq-flags state precisely:
5454 static noinstr void check_flags(unsigned long flags)
5456 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5460 /* Get the warning out.. */
5461 instrumentation_begin();
5463 if (irqs_disabled_flags(flags)) {
5464 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5465 printk("possible reason: unannotated irqs-off.\n");
5468 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5469 printk("possible reason: unannotated irqs-on.\n");
5474 * We dont accurately track softirq state in e.g.
5475 * hardirq contexts (such as on 4KSTACKS), so only
5476 * check if not in hardirq contexts:
5478 if (!hardirq_count()) {
5479 if (softirq_count()) {
5480 /* like the above, but with softirqs */
5481 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5483 /* lick the above, does it taste good? */
5484 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5489 print_irqtrace_events(current);
5491 instrumentation_end();
5495 void lock_set_class(struct lockdep_map *lock, const char *name,
5496 struct lock_class_key *key, unsigned int subclass,
5499 unsigned long flags;
5501 if (unlikely(!lockdep_enabled()))
5504 raw_local_irq_save(flags);
5505 lockdep_recursion_inc();
5507 if (__lock_set_class(lock, name, key, subclass, ip))
5508 check_chain_key(current);
5509 lockdep_recursion_finish();
5510 raw_local_irq_restore(flags);
5512 EXPORT_SYMBOL_GPL(lock_set_class);
5514 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5516 unsigned long flags;
5518 if (unlikely(!lockdep_enabled()))
5521 raw_local_irq_save(flags);
5522 lockdep_recursion_inc();
5524 if (__lock_downgrade(lock, ip))
5525 check_chain_key(current);
5526 lockdep_recursion_finish();
5527 raw_local_irq_restore(flags);
5529 EXPORT_SYMBOL_GPL(lock_downgrade);
5531 /* NMI context !!! */
5532 static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5534 #ifdef CONFIG_PROVE_LOCKING
5535 struct lock_class *class = look_up_lock_class(lock, subclass);
5536 unsigned long mask = LOCKF_USED;
5538 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5543 * READ locks only conflict with USED, such that if we only ever use
5544 * READ locks, there is no deadlock possible -- RCU.
5547 mask |= LOCKF_USED_READ;
5549 if (!(class->usage_mask & mask))
5552 hlock->class_idx = class - lock_classes;
5554 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5558 static bool lockdep_nmi(void)
5560 if (raw_cpu_read(lockdep_recursion))
5570 * read_lock() is recursive if:
5571 * 1. We force lockdep think this way in selftests or
5572 * 2. The implementation is not queued read/write lock or
5573 * 3. The locker is at an in_interrupt() context.
5575 bool read_lock_is_recursive(void)
5577 return force_read_lock_recursive ||
5578 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5581 EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5584 * We are not always called with irqs disabled - do that here,
5585 * and also avoid lockdep recursion:
5587 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5588 int trylock, int read, int check,
5589 struct lockdep_map *nest_lock, unsigned long ip)
5591 unsigned long flags;
5593 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5598 if (unlikely(!lockdep_enabled())) {
5599 /* XXX allow trylock from NMI ?!? */
5600 if (lockdep_nmi() && !trylock) {
5601 struct held_lock hlock;
5603 hlock.acquire_ip = ip;
5604 hlock.instance = lock;
5605 hlock.nest_lock = nest_lock;
5606 hlock.irq_context = 2; // XXX
5607 hlock.trylock = trylock;
5609 hlock.check = check;
5610 hlock.hardirqs_off = true;
5611 hlock.references = 0;
5613 verify_lock_unused(lock, &hlock, subclass);
5618 raw_local_irq_save(flags);
5621 lockdep_recursion_inc();
5622 __lock_acquire(lock, subclass, trylock, read, check,
5623 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
5624 lockdep_recursion_finish();
5625 raw_local_irq_restore(flags);
5627 EXPORT_SYMBOL_GPL(lock_acquire);
5629 void lock_release(struct lockdep_map *lock, unsigned long ip)
5631 unsigned long flags;
5633 trace_lock_release(lock, ip);
5635 if (unlikely(!lockdep_enabled()))
5638 raw_local_irq_save(flags);
5641 lockdep_recursion_inc();
5642 if (__lock_release(lock, ip))
5643 check_chain_key(current);
5644 lockdep_recursion_finish();
5645 raw_local_irq_restore(flags);
5647 EXPORT_SYMBOL_GPL(lock_release);
5649 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5651 unsigned long flags;
5652 int ret = LOCK_STATE_NOT_HELD;
5655 * Avoid false negative lockdep_assert_held() and
5656 * lockdep_assert_not_held().
5658 if (unlikely(!lockdep_enabled()))
5659 return LOCK_STATE_UNKNOWN;
5661 raw_local_irq_save(flags);
5664 lockdep_recursion_inc();
5665 ret = __lock_is_held(lock, read);
5666 lockdep_recursion_finish();
5667 raw_local_irq_restore(flags);
5671 EXPORT_SYMBOL_GPL(lock_is_held_type);
5672 NOKPROBE_SYMBOL(lock_is_held_type);
5674 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5676 struct pin_cookie cookie = NIL_COOKIE;
5677 unsigned long flags;
5679 if (unlikely(!lockdep_enabled()))
5682 raw_local_irq_save(flags);
5685 lockdep_recursion_inc();
5686 cookie = __lock_pin_lock(lock);
5687 lockdep_recursion_finish();
5688 raw_local_irq_restore(flags);
5692 EXPORT_SYMBOL_GPL(lock_pin_lock);
5694 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5696 unsigned long flags;
5698 if (unlikely(!lockdep_enabled()))
5701 raw_local_irq_save(flags);
5704 lockdep_recursion_inc();
5705 __lock_repin_lock(lock, cookie);
5706 lockdep_recursion_finish();
5707 raw_local_irq_restore(flags);
5709 EXPORT_SYMBOL_GPL(lock_repin_lock);
5711 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5713 unsigned long flags;
5715 if (unlikely(!lockdep_enabled()))
5718 raw_local_irq_save(flags);
5721 lockdep_recursion_inc();
5722 __lock_unpin_lock(lock, cookie);
5723 lockdep_recursion_finish();
5724 raw_local_irq_restore(flags);
5726 EXPORT_SYMBOL_GPL(lock_unpin_lock);
5728 #ifdef CONFIG_LOCK_STAT
5729 static void print_lock_contention_bug(struct task_struct *curr,
5730 struct lockdep_map *lock,
5733 if (!debug_locks_off())
5735 if (debug_locks_silent)
5739 pr_warn("=================================\n");
5740 pr_warn("WARNING: bad contention detected!\n");
5741 print_kernel_ident();
5742 pr_warn("---------------------------------\n");
5743 pr_warn("%s/%d is trying to contend lock (",
5744 curr->comm, task_pid_nr(curr));
5745 print_lockdep_cache(lock);
5747 print_ip_sym(KERN_WARNING, ip);
5748 pr_warn("but there are no locks held!\n");
5749 pr_warn("\nother info that might help us debug this:\n");
5750 lockdep_print_held_locks(curr);
5752 pr_warn("\nstack backtrace:\n");
5757 __lock_contended(struct lockdep_map *lock, unsigned long ip)
5759 struct task_struct *curr = current;
5760 struct held_lock *hlock;
5761 struct lock_class_stats *stats;
5763 int i, contention_point, contending_point;
5765 depth = curr->lockdep_depth;
5767 * Whee, we contended on this lock, except it seems we're not
5768 * actually trying to acquire anything much at all..
5770 if (DEBUG_LOCKS_WARN_ON(!depth))
5773 hlock = find_held_lock(curr, lock, depth, &i);
5775 print_lock_contention_bug(curr, lock, ip);
5779 if (hlock->instance != lock)
5782 hlock->waittime_stamp = lockstat_clock();
5784 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
5785 contending_point = lock_point(hlock_class(hlock)->contending_point,
5788 stats = get_lock_stats(hlock_class(hlock));
5789 if (contention_point < LOCKSTAT_POINTS)
5790 stats->contention_point[contention_point]++;
5791 if (contending_point < LOCKSTAT_POINTS)
5792 stats->contending_point[contending_point]++;
5793 if (lock->cpu != smp_processor_id())
5794 stats->bounces[bounce_contended + !!hlock->read]++;
5798 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
5800 struct task_struct *curr = current;
5801 struct held_lock *hlock;
5802 struct lock_class_stats *stats;
5804 u64 now, waittime = 0;
5807 depth = curr->lockdep_depth;
5809 * Yay, we acquired ownership of this lock we didn't try to
5810 * acquire, how the heck did that happen?
5812 if (DEBUG_LOCKS_WARN_ON(!depth))
5815 hlock = find_held_lock(curr, lock, depth, &i);
5817 print_lock_contention_bug(curr, lock, _RET_IP_);
5821 if (hlock->instance != lock)
5824 cpu = smp_processor_id();
5825 if (hlock->waittime_stamp) {
5826 now = lockstat_clock();
5827 waittime = now - hlock->waittime_stamp;
5828 hlock->holdtime_stamp = now;
5831 stats = get_lock_stats(hlock_class(hlock));
5834 lock_time_inc(&stats->read_waittime, waittime);
5836 lock_time_inc(&stats->write_waittime, waittime);
5838 if (lock->cpu != cpu)
5839 stats->bounces[bounce_acquired + !!hlock->read]++;
5845 void lock_contended(struct lockdep_map *lock, unsigned long ip)
5847 unsigned long flags;
5849 trace_lock_contended(lock, ip);
5851 if (unlikely(!lock_stat || !lockdep_enabled()))
5854 raw_local_irq_save(flags);
5856 lockdep_recursion_inc();
5857 __lock_contended(lock, ip);
5858 lockdep_recursion_finish();
5859 raw_local_irq_restore(flags);
5861 EXPORT_SYMBOL_GPL(lock_contended);
5863 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
5865 unsigned long flags;
5867 trace_lock_acquired(lock, ip);
5869 if (unlikely(!lock_stat || !lockdep_enabled()))
5872 raw_local_irq_save(flags);
5874 lockdep_recursion_inc();
5875 __lock_acquired(lock, ip);
5876 lockdep_recursion_finish();
5877 raw_local_irq_restore(flags);
5879 EXPORT_SYMBOL_GPL(lock_acquired);
5883 * Used by the testsuite, sanitize the validator state
5884 * after a simulated failure:
5887 void lockdep_reset(void)
5889 unsigned long flags;
5892 raw_local_irq_save(flags);
5893 lockdep_init_task(current);
5894 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
5895 nr_hardirq_chains = 0;
5896 nr_softirq_chains = 0;
5897 nr_process_chains = 0;
5899 for (i = 0; i < CHAINHASH_SIZE; i++)
5900 INIT_HLIST_HEAD(chainhash_table + i);
5901 raw_local_irq_restore(flags);
5904 /* Remove a class from a lock chain. Must be called with the graph lock held. */
5905 static void remove_class_from_lock_chain(struct pending_free *pf,
5906 struct lock_chain *chain,
5907 struct lock_class *class)
5909 #ifdef CONFIG_PROVE_LOCKING
5912 for (i = chain->base; i < chain->base + chain->depth; i++) {
5913 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
5916 * Each lock class occurs at most once in a lock chain so once
5917 * we found a match we can break out of this loop.
5919 goto free_lock_chain;
5921 /* Since the chain has not been modified, return. */
5925 free_chain_hlocks(chain->base, chain->depth);
5926 /* Overwrite the chain key for concurrent RCU readers. */
5927 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
5928 dec_chains(chain->irq_context);
5931 * Note: calling hlist_del_rcu() from inside a
5932 * hlist_for_each_entry_rcu() loop is safe.
5934 hlist_del_rcu(&chain->entry);
5935 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
5936 nr_zapped_lock_chains++;
5940 /* Must be called with the graph lock held. */
5941 static void remove_class_from_lock_chains(struct pending_free *pf,
5942 struct lock_class *class)
5944 struct lock_chain *chain;
5945 struct hlist_head *head;
5948 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
5949 head = chainhash_table + i;
5950 hlist_for_each_entry_rcu(chain, head, entry) {
5951 remove_class_from_lock_chain(pf, chain, class);
5957 * Remove all references to a lock class. The caller must hold the graph lock.
5959 static void zap_class(struct pending_free *pf, struct lock_class *class)
5961 struct lock_list *entry;
5964 WARN_ON_ONCE(!class->key);
5967 * Remove all dependencies this lock is
5970 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
5971 entry = list_entries + i;
5972 if (entry->class != class && entry->links_to != class)
5974 __clear_bit(i, list_entries_in_use);
5976 list_del_rcu(&entry->entry);
5978 if (list_empty(&class->locks_after) &&
5979 list_empty(&class->locks_before)) {
5980 list_move_tail(&class->lock_entry, &pf->zapped);
5981 hlist_del_rcu(&class->hash_entry);
5982 WRITE_ONCE(class->key, NULL);
5983 WRITE_ONCE(class->name, NULL);
5985 __clear_bit(class - lock_classes, lock_classes_in_use);
5986 if (class - lock_classes == max_lock_class_idx)
5987 max_lock_class_idx--;
5989 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
5993 remove_class_from_lock_chains(pf, class);
5994 nr_zapped_classes++;
5997 static void reinit_class(struct lock_class *class)
5999 void *const p = class;
6000 const unsigned int offset = offsetof(struct lock_class, key);
6002 WARN_ON_ONCE(!class->lock_entry.next);
6003 WARN_ON_ONCE(!list_empty(&class->locks_after));
6004 WARN_ON_ONCE(!list_empty(&class->locks_before));
6005 memset(p + offset, 0, sizeof(*class) - offset);
6006 WARN_ON_ONCE(!class->lock_entry.next);
6007 WARN_ON_ONCE(!list_empty(&class->locks_after));
6008 WARN_ON_ONCE(!list_empty(&class->locks_before));
6011 static inline int within(const void *addr, void *start, unsigned long size)
6013 return addr >= start && addr < start + size;
6016 static bool inside_selftest(void)
6018 return current == lockdep_selftest_task_struct;
6021 /* The caller must hold the graph lock. */
6022 static struct pending_free *get_pending_free(void)
6024 return delayed_free.pf + delayed_free.index;
6027 static void free_zapped_rcu(struct rcu_head *cb);
6030 * Schedule an RCU callback if no RCU callback is pending. Must be called with
6031 * the graph lock held.
6033 static void call_rcu_zapped(struct pending_free *pf)
6035 WARN_ON_ONCE(inside_selftest());
6037 if (list_empty(&pf->zapped))
6040 if (delayed_free.scheduled)
6043 delayed_free.scheduled = true;
6045 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
6046 delayed_free.index ^= 1;
6048 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6051 /* The caller must hold the graph lock. May be called from RCU context. */
6052 static void __free_zapped_classes(struct pending_free *pf)
6054 struct lock_class *class;
6056 check_data_structures();
6058 list_for_each_entry(class, &pf->zapped, lock_entry)
6059 reinit_class(class);
6061 list_splice_init(&pf->zapped, &free_lock_classes);
6063 #ifdef CONFIG_PROVE_LOCKING
6064 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
6065 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
6066 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
6070 static void free_zapped_rcu(struct rcu_head *ch)
6072 struct pending_free *pf;
6073 unsigned long flags;
6075 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
6078 raw_local_irq_save(flags);
6082 pf = delayed_free.pf + (delayed_free.index ^ 1);
6083 __free_zapped_classes(pf);
6084 delayed_free.scheduled = false;
6087 * If there's anything on the open list, close and start a new callback.
6089 call_rcu_zapped(delayed_free.pf + delayed_free.index);
6092 raw_local_irq_restore(flags);
6096 * Remove all lock classes from the class hash table and from the
6097 * all_lock_classes list whose key or name is in the address range [start,
6098 * start + size). Move these lock classes to the zapped_classes list. Must
6099 * be called with the graph lock held.
6101 static void __lockdep_free_key_range(struct pending_free *pf, void *start,
6104 struct lock_class *class;
6105 struct hlist_head *head;
6108 /* Unhash all classes that were created by a module. */
6109 for (i = 0; i < CLASSHASH_SIZE; i++) {
6110 head = classhash_table + i;
6111 hlist_for_each_entry_rcu(class, head, hash_entry) {
6112 if (!within(class->key, start, size) &&
6113 !within(class->name, start, size))
6115 zap_class(pf, class);
6121 * Used in module.c to remove lock classes from memory that is going to be
6122 * freed; and possibly re-used by other modules.
6124 * We will have had one synchronize_rcu() before getting here, so we're
6125 * guaranteed nobody will look up these exact classes -- they're properly dead
6126 * but still allocated.
6128 static void lockdep_free_key_range_reg(void *start, unsigned long size)
6130 struct pending_free *pf;
6131 unsigned long flags;
6133 init_data_structures_once();
6135 raw_local_irq_save(flags);
6137 pf = get_pending_free();
6138 __lockdep_free_key_range(pf, start, size);
6139 call_rcu_zapped(pf);
6141 raw_local_irq_restore(flags);
6144 * Wait for any possible iterators from look_up_lock_class() to pass
6145 * before continuing to free the memory they refer to.
6151 * Free all lockdep keys in the range [start, start+size). Does not sleep.
6152 * Ignores debug_locks. Must only be used by the lockdep selftests.
6154 static void lockdep_free_key_range_imm(void *start, unsigned long size)
6156 struct pending_free *pf = delayed_free.pf;
6157 unsigned long flags;
6159 init_data_structures_once();
6161 raw_local_irq_save(flags);
6163 __lockdep_free_key_range(pf, start, size);
6164 __free_zapped_classes(pf);
6166 raw_local_irq_restore(flags);
6169 void lockdep_free_key_range(void *start, unsigned long size)
6171 init_data_structures_once();
6173 if (inside_selftest())
6174 lockdep_free_key_range_imm(start, size);
6176 lockdep_free_key_range_reg(start, size);
6180 * Check whether any element of the @lock->class_cache[] array refers to a
6181 * registered lock class. The caller must hold either the graph lock or the
6184 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
6186 struct lock_class *class;
6187 struct hlist_head *head;
6190 for (i = 0; i < CLASSHASH_SIZE; i++) {
6191 head = classhash_table + i;
6192 hlist_for_each_entry_rcu(class, head, hash_entry) {
6193 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6194 if (lock->class_cache[j] == class)
6201 /* The caller must hold the graph lock. Does not sleep. */
6202 static void __lockdep_reset_lock(struct pending_free *pf,
6203 struct lockdep_map *lock)
6205 struct lock_class *class;
6209 * Remove all classes this lock might have:
6211 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6213 * If the class exists we look it up and zap it:
6215 class = look_up_lock_class(lock, j);
6217 zap_class(pf, class);
6220 * Debug check: in the end all mapped classes should
6223 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6228 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6229 * released data structures from RCU context.
6231 static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6233 struct pending_free *pf;
6234 unsigned long flags;
6237 raw_local_irq_save(flags);
6238 locked = graph_lock();
6242 pf = get_pending_free();
6243 __lockdep_reset_lock(pf, lock);
6244 call_rcu_zapped(pf);
6248 raw_local_irq_restore(flags);
6252 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6253 * lockdep selftests.
6255 static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6257 struct pending_free *pf = delayed_free.pf;
6258 unsigned long flags;
6260 raw_local_irq_save(flags);
6262 __lockdep_reset_lock(pf, lock);
6263 __free_zapped_classes(pf);
6265 raw_local_irq_restore(flags);
6268 void lockdep_reset_lock(struct lockdep_map *lock)
6270 init_data_structures_once();
6272 if (inside_selftest())
6273 lockdep_reset_lock_imm(lock);
6275 lockdep_reset_lock_reg(lock);
6279 * Unregister a dynamically allocated key.
6281 * Unlike lockdep_register_key(), a search is always done to find a matching
6282 * key irrespective of debug_locks to avoid potential invalid access to freed
6283 * memory in lock_class entry.
6285 void lockdep_unregister_key(struct lock_class_key *key)
6287 struct hlist_head *hash_head = keyhashentry(key);
6288 struct lock_class_key *k;
6289 struct pending_free *pf;
6290 unsigned long flags;
6295 if (WARN_ON_ONCE(static_obj(key)))
6298 raw_local_irq_save(flags);
6301 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6303 hlist_del_rcu(&k->hash_entry);
6308 WARN_ON_ONCE(!found && debug_locks);
6310 pf = get_pending_free();
6311 __lockdep_free_key_range(pf, key, 1);
6312 call_rcu_zapped(pf);
6315 raw_local_irq_restore(flags);
6317 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6320 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6322 void __init lockdep_init(void)
6324 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6326 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6327 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6328 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6329 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6330 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6331 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6332 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6334 printk(" memory used by lock dependency info: %zu kB\n",
6335 (sizeof(lock_classes) +
6336 sizeof(lock_classes_in_use) +
6337 sizeof(classhash_table) +
6338 sizeof(list_entries) +
6339 sizeof(list_entries_in_use) +
6340 sizeof(chainhash_table) +
6341 sizeof(delayed_free)
6342 #ifdef CONFIG_PROVE_LOCKING
6344 + sizeof(lock_chains)
6345 + sizeof(lock_chains_in_use)
6346 + sizeof(chain_hlocks)
6351 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6352 printk(" memory used for stack traces: %zu kB\n",
6353 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6357 printk(" per task-struct memory footprint: %zu bytes\n",
6358 sizeof(((struct task_struct *)NULL)->held_locks));
6362 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6363 const void *mem_to, struct held_lock *hlock)
6365 if (!debug_locks_off())
6367 if (debug_locks_silent)
6371 pr_warn("=========================\n");
6372 pr_warn("WARNING: held lock freed!\n");
6373 print_kernel_ident();
6374 pr_warn("-------------------------\n");
6375 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6376 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6378 lockdep_print_held_locks(curr);
6380 pr_warn("\nstack backtrace:\n");
6384 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6385 const void* lock_from, unsigned long lock_len)
6387 return lock_from + lock_len <= mem_from ||
6388 mem_from + mem_len <= lock_from;
6392 * Called when kernel memory is freed (or unmapped), or if a lock
6393 * is destroyed or reinitialized - this code checks whether there is
6394 * any held lock in the memory range of <from> to <to>:
6396 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6398 struct task_struct *curr = current;
6399 struct held_lock *hlock;
6400 unsigned long flags;
6403 if (unlikely(!debug_locks))
6406 raw_local_irq_save(flags);
6407 for (i = 0; i < curr->lockdep_depth; i++) {
6408 hlock = curr->held_locks + i;
6410 if (not_in_range(mem_from, mem_len, hlock->instance,
6411 sizeof(*hlock->instance)))
6414 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6417 raw_local_irq_restore(flags);
6419 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6421 static void print_held_locks_bug(void)
6423 if (!debug_locks_off())
6425 if (debug_locks_silent)
6429 pr_warn("====================================\n");
6430 pr_warn("WARNING: %s/%d still has locks held!\n",
6431 current->comm, task_pid_nr(current));
6432 print_kernel_ident();
6433 pr_warn("------------------------------------\n");
6434 lockdep_print_held_locks(current);
6435 pr_warn("\nstack backtrace:\n");
6439 void debug_check_no_locks_held(void)
6441 if (unlikely(current->lockdep_depth > 0))
6442 print_held_locks_bug();
6444 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6447 void debug_show_all_locks(void)
6449 struct task_struct *g, *p;
6451 if (unlikely(!debug_locks)) {
6452 pr_warn("INFO: lockdep is turned off.\n");
6455 pr_warn("\nShowing all locks held in the system:\n");
6458 for_each_process_thread(g, p) {
6459 if (!p->lockdep_depth)
6461 lockdep_print_held_locks(p);
6462 touch_nmi_watchdog();
6463 touch_all_softlockup_watchdogs();
6468 pr_warn("=============================================\n\n");
6470 EXPORT_SYMBOL_GPL(debug_show_all_locks);
6474 * Careful: only use this function if you are sure that
6475 * the task cannot run in parallel!
6477 void debug_show_held_locks(struct task_struct *task)
6479 if (unlikely(!debug_locks)) {
6480 printk("INFO: lockdep is turned off.\n");
6483 lockdep_print_held_locks(task);
6485 EXPORT_SYMBOL_GPL(debug_show_held_locks);
6487 asmlinkage __visible void lockdep_sys_exit(void)
6489 struct task_struct *curr = current;
6491 if (unlikely(curr->lockdep_depth)) {
6492 if (!debug_locks_off())
6495 pr_warn("================================================\n");
6496 pr_warn("WARNING: lock held when returning to user space!\n");
6497 print_kernel_ident();
6498 pr_warn("------------------------------------------------\n");
6499 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6500 curr->comm, curr->pid);
6501 lockdep_print_held_locks(curr);
6505 * The lock history for each syscall should be independent. So wipe the
6506 * slate clean on return to userspace.
6508 lockdep_invariant_state(false);
6511 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6513 struct task_struct *curr = current;
6514 int dl = READ_ONCE(debug_locks);
6516 /* Note: the following can be executed concurrently, so be careful. */
6518 pr_warn("=============================\n");
6519 pr_warn("WARNING: suspicious RCU usage\n");
6520 print_kernel_ident();
6521 pr_warn("-----------------------------\n");
6522 pr_warn("%s:%d %s!\n", file, line, s);
6523 pr_warn("\nother info that might help us debug this:\n\n");
6524 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
6525 !rcu_lockdep_current_cpu_online()
6526 ? "RCU used illegally from offline CPU!\n"
6528 rcu_scheduler_active, dl,
6529 dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
6532 * If a CPU is in the RCU-free window in idle (ie: in the section
6533 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
6534 * considers that CPU to be in an "extended quiescent state",
6535 * which means that RCU will be completely ignoring that CPU.
6536 * Therefore, rcu_read_lock() and friends have absolutely no
6537 * effect on a CPU running in that state. In other words, even if
6538 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6539 * delete data structures out from under it. RCU really has no
6540 * choice here: we need to keep an RCU-free window in idle where
6541 * the CPU may possibly enter into low power mode. This way we can
6542 * notice an extended quiescent state to other CPUs that started a grace
6543 * period. Otherwise we would delay any grace period as long as we run
6546 * So complain bitterly if someone does call rcu_read_lock(),
6547 * rcu_read_lock_bh() and so on from extended quiescent states.
6549 if (!rcu_is_watching())
6550 pr_warn("RCU used illegally from extended quiescent state!\n");
6552 lockdep_print_held_locks(curr);
6553 pr_warn("\nstack backtrace:\n");
6556 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);