GNU Linux-libre 6.9.2-gnu
[releases.git] / include / linux / srcutree.h
1 /* SPDX-License-Identifier: GPL-2.0+ */
2 /*
3  * Sleepable Read-Copy Update mechanism for mutual exclusion,
4  *      tree variant.
5  *
6  * Copyright (C) IBM Corporation, 2017
7  *
8  * Author: Paul McKenney <paulmck@linux.ibm.com>
9  */
10
11 #ifndef _LINUX_SRCU_TREE_H
12 #define _LINUX_SRCU_TREE_H
13
14 #include <linux/rcu_node_tree.h>
15 #include <linux/completion.h>
16
17 struct srcu_node;
18 struct srcu_struct;
19
20 /*
21  * Per-CPU structure feeding into leaf srcu_node, similar in function
22  * to rcu_node.
23  */
24 struct srcu_data {
25         /* Read-side state. */
26         atomic_long_t srcu_lock_count[2];       /* Locks per CPU. */
27         atomic_long_t srcu_unlock_count[2];     /* Unlocks per CPU. */
28         int srcu_nmi_safety;                    /* NMI-safe srcu_struct structure? */
29
30         /* Update-side state. */
31         spinlock_t __private lock ____cacheline_internodealigned_in_smp;
32         struct rcu_segcblist srcu_cblist;       /* List of callbacks.*/
33         unsigned long srcu_gp_seq_needed;       /* Furthest future GP needed. */
34         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
35         bool srcu_cblist_invoking;              /* Invoking these CBs? */
36         struct timer_list delay_work;           /* Delay for CB invoking */
37         struct work_struct work;                /* Context for CB invoking. */
38         struct rcu_head srcu_barrier_head;      /* For srcu_barrier() use. */
39         struct srcu_node *mynode;               /* Leaf srcu_node. */
40         unsigned long grpmask;                  /* Mask for leaf srcu_node */
41                                                 /*  ->srcu_data_have_cbs[]. */
42         int cpu;
43         struct srcu_struct *ssp;
44 };
45
46 /*
47  * Node in SRCU combining tree, similar in function to rcu_data.
48  */
49 struct srcu_node {
50         spinlock_t __private lock;
51         unsigned long srcu_have_cbs[4];         /* GP seq for children having CBs, but only */
52                                                 /*  if greater than ->srcu_gp_seq. */
53         unsigned long srcu_data_have_cbs[4];    /* Which srcu_data structs have CBs for given GP? */
54         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
55         struct srcu_node *srcu_parent;          /* Next up in tree. */
56         int grplo;                              /* Least CPU for node. */
57         int grphi;                              /* Biggest CPU for node. */
58 };
59
60 /*
61  * Per-SRCU-domain structure, update-side data linked from srcu_struct.
62  */
63 struct srcu_usage {
64         struct srcu_node *node;                 /* Combining tree. */
65         struct srcu_node *level[RCU_NUM_LVLS + 1];
66                                                 /* First node at each level. */
67         int srcu_size_state;                    /* Small-to-big transition state. */
68         struct mutex srcu_cb_mutex;             /* Serialize CB preparation. */
69         spinlock_t __private lock;              /* Protect counters and size state. */
70         struct mutex srcu_gp_mutex;             /* Serialize GP work. */
71         unsigned long srcu_gp_seq;              /* Grace-period seq #. */
72         unsigned long srcu_gp_seq_needed;       /* Latest gp_seq needed. */
73         unsigned long srcu_gp_seq_needed_exp;   /* Furthest future exp GP. */
74         unsigned long srcu_gp_start;            /* Last GP start timestamp (jiffies) */
75         unsigned long srcu_last_gp_end;         /* Last GP end timestamp (ns) */
76         unsigned long srcu_size_jiffies;        /* Current contention-measurement interval. */
77         unsigned long srcu_n_lock_retries;      /* Contention events in current interval. */
78         unsigned long srcu_n_exp_nodelay;       /* # expedited no-delays in current GP phase. */
79         bool sda_is_static;                     /* May ->sda be passed to free_percpu()? */
80         unsigned long srcu_barrier_seq;         /* srcu_barrier seq #. */
81         struct mutex srcu_barrier_mutex;        /* Serialize barrier ops. */
82         struct completion srcu_barrier_completion;
83                                                 /* Awaken barrier rq at end. */
84         atomic_t srcu_barrier_cpu_cnt;          /* # CPUs not yet posting a */
85                                                 /*  callback for the barrier */
86                                                 /*  operation. */
87         unsigned long reschedule_jiffies;
88         unsigned long reschedule_count;
89         struct delayed_work work;
90         struct srcu_struct *srcu_ssp;
91 };
92
93 /*
94  * Per-SRCU-domain structure, similar in function to rcu_state.
95  */
96 struct srcu_struct {
97         unsigned int srcu_idx;                  /* Current rdr array element. */
98         struct srcu_data __percpu *sda;         /* Per-CPU srcu_data array. */
99         struct lockdep_map dep_map;
100         struct srcu_usage *srcu_sup;            /* Update-side data. */
101 };
102
103 // Values for size state variable (->srcu_size_state).  Once the state
104 // has been set to SRCU_SIZE_ALLOC, the grace-period code advances through
105 // this state machine one step per grace period until the SRCU_SIZE_BIG state
106 // is reached.  Otherwise, the state machine remains in the SRCU_SIZE_SMALL
107 // state indefinitely.
108 #define SRCU_SIZE_SMALL         0       // No srcu_node combining tree, ->node == NULL
109 #define SRCU_SIZE_ALLOC         1       // An srcu_node tree is being allocated, initialized,
110                                         //  and then referenced by ->node.  It will not be used.
111 #define SRCU_SIZE_WAIT_BARRIER  2       // The srcu_node tree starts being used by everything
112                                         //  except call_srcu(), especially by srcu_barrier().
113                                         //  By the end of this state, all CPUs and threads
114                                         //  are aware of this tree's existence.
115 #define SRCU_SIZE_WAIT_CALL     3       // The srcu_node tree starts being used by call_srcu().
116                                         //  By the end of this state, all of the call_srcu()
117                                         //  invocations that were running on a non-boot CPU
118                                         //  and using the boot CPU's callback queue will have
119                                         //  completed.
120 #define SRCU_SIZE_WAIT_CBS1     4       // Don't trust the ->srcu_have_cbs[] grace-period
121 #define SRCU_SIZE_WAIT_CBS2     5       //  sequence elements or the ->srcu_data_have_cbs[]
122 #define SRCU_SIZE_WAIT_CBS3     6       //  CPU-bitmask elements until all four elements of
123 #define SRCU_SIZE_WAIT_CBS4     7       //  each array have been initialized.
124 #define SRCU_SIZE_BIG           8       // The srcu_node combining tree is fully initialized
125                                         //  and all aspects of it are being put to use.
126
127 /* Values for state variable (bottom bits of ->srcu_gp_seq). */
128 #define SRCU_STATE_IDLE         0
129 #define SRCU_STATE_SCAN1        1
130 #define SRCU_STATE_SCAN2        2
131
132 #define __SRCU_USAGE_INIT(name)                                                                 \
133 {                                                                                               \
134         .lock = __SPIN_LOCK_UNLOCKED(name.lock),                                                \
135         .srcu_gp_seq_needed = -1UL,                                                             \
136         .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0),                                 \
137 }
138
139 #define __SRCU_STRUCT_INIT_COMMON(name, usage_name)                                             \
140         .srcu_sup = &usage_name,                                                                \
141         __SRCU_DEP_MAP_INIT(name)
142
143 #define __SRCU_STRUCT_INIT_MODULE(name, usage_name)                                             \
144 {                                                                                               \
145         __SRCU_STRUCT_INIT_COMMON(name, usage_name)                                             \
146 }
147
148 #define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name)                                         \
149 {                                                                                               \
150         .sda = &pcpu_name,                                                                      \
151         __SRCU_STRUCT_INIT_COMMON(name, usage_name)                                             \
152 }
153
154 /*
155  * Define and initialize a srcu struct at build time.
156  * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
157  *
158  * Note that although DEFINE_STATIC_SRCU() hides the name from other
159  * files, the per-CPU variable rules nevertheless require that the
160  * chosen name be globally unique.  These rules also prohibit use of
161  * DEFINE_STATIC_SRCU() within a function.  If these rules are too
162  * restrictive, declare the srcu_struct manually.  For example, in
163  * each file:
164  *
165  *      static struct srcu_struct my_srcu;
166  *
167  * Then, before the first use of each my_srcu, manually initialize it:
168  *
169  *      init_srcu_struct(&my_srcu);
170  *
171  * See include/linux/percpu-defs.h for the rules on per-CPU variables.
172  */
173 #ifdef MODULE
174 # define __DEFINE_SRCU(name, is_static)                                                         \
175         static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage);      \
176         is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage); \
177         extern struct srcu_struct * const __srcu_struct_##name;                                 \
178         struct srcu_struct * const __srcu_struct_##name                                         \
179                 __section("___srcu_struct_ptrs") = &name
180 #else
181 # define __DEFINE_SRCU(name, is_static)                                                         \
182         static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);                              \
183         static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage);      \
184         is_static struct srcu_struct name =                                                     \
185                 __SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)
186 #endif
187 #define DEFINE_SRCU(name)               __DEFINE_SRCU(name, /* not static */)
188 #define DEFINE_STATIC_SRCU(name)        __DEFINE_SRCU(name, static)
189
190 void synchronize_srcu_expedited(struct srcu_struct *ssp);
191 void srcu_barrier(struct srcu_struct *ssp);
192 void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
193
194 #endif