1 /* SPDX-License-Identifier: GPL-2.0-only */
3 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
6 #ifndef __ASM_SPINLOCK_H
7 #define __ASM_SPINLOCK_H
9 #include <asm/spinlock_types.h>
10 #include <asm/processor.h>
11 #include <asm/barrier.h>
13 #define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
15 #ifdef CONFIG_ARC_HAS_LLSC
17 static inline void arch_spin_lock(arch_spinlock_t *lock)
22 "1: llock %[val], [%[slock]] \n"
23 " breq %[val], %[LOCKED], 1b \n" /* spin while LOCKED */
24 " scond %[LOCKED], [%[slock]] \n" /* acquire */
28 : [slock] "r" (&(lock->slock)),
29 [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
33 * ACQUIRE barrier to ensure load/store after taking the lock
34 * don't "bleed-up" out of the critical section (leak-in is allowed)
35 * http://www.spinics.net/lists/kernel/msg2010409.html
37 * ARCv2 only has load-load, store-store and all-all barrier
38 * thus need the full all-all barrier
43 /* 1 - lock taken successfully */
44 static inline int arch_spin_trylock(arch_spinlock_t *lock)
46 unsigned int val, got_it = 0;
49 "1: llock %[val], [%[slock]] \n"
50 " breq %[val], %[LOCKED], 4f \n" /* already LOCKED, just bail */
51 " scond %[LOCKED], [%[slock]] \n" /* acquire */
53 " mov %[got_it], 1 \n"
57 [got_it] "+&r" (got_it)
58 : [slock] "r" (&(lock->slock)),
59 [LOCKED] "r" (__ARCH_SPIN_LOCK_LOCKED__)
67 static inline void arch_spin_unlock(arch_spinlock_t *lock)
71 WRITE_ONCE(lock->slock, __ARCH_SPIN_LOCK_UNLOCKED__);
75 * Read-write spinlocks, allowing multiple readers but only one writer.
76 * Unfair locking as Writers could be starved indefinitely by Reader(s)
79 static inline void arch_read_lock(arch_rwlock_t *rw)
84 * zero means writer holds the lock exclusively, deny Reader.
85 * Otherwise grant lock to first/subseq reader
87 * if (rw->counter > 0) {
94 "1: llock %[val], [%[rwlock]] \n"
95 " brls %[val], %[WR_LOCKED], 1b\n" /* <= 0: spin while write locked */
96 " sub %[val], %[val], 1 \n" /* reader lock */
97 " scond %[val], [%[rwlock]] \n"
101 : [rwlock] "r" (&(rw->counter)),
108 /* 1 - lock taken successfully */
109 static inline int arch_read_trylock(arch_rwlock_t *rw)
111 unsigned int val, got_it = 0;
113 __asm__ __volatile__(
114 "1: llock %[val], [%[rwlock]] \n"
115 " brls %[val], %[WR_LOCKED], 4f\n" /* <= 0: already write locked, bail */
116 " sub %[val], %[val], 1 \n" /* counter-- */
117 " scond %[val], [%[rwlock]] \n"
118 " bnz 1b \n" /* retry if collided with someone */
119 " mov %[got_it], 1 \n"
121 "4: ; --- done --- \n"
124 [got_it] "+&r" (got_it)
125 : [rwlock] "r" (&(rw->counter)),
134 static inline void arch_write_lock(arch_rwlock_t *rw)
139 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
140 * deny writer. Otherwise if unlocked grant to writer
141 * Hence the claim that Linux rwlocks are unfair to writers.
142 * (can be starved for an indefinite time by readers).
144 * if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
150 __asm__ __volatile__(
151 "1: llock %[val], [%[rwlock]] \n"
152 " brne %[val], %[UNLOCKED], 1b \n" /* while !UNLOCKED spin */
153 " mov %[val], %[WR_LOCKED] \n"
154 " scond %[val], [%[rwlock]] \n"
158 : [rwlock] "r" (&(rw->counter)),
159 [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
166 /* 1 - lock taken successfully */
167 static inline int arch_write_trylock(arch_rwlock_t *rw)
169 unsigned int val, got_it = 0;
171 __asm__ __volatile__(
172 "1: llock %[val], [%[rwlock]] \n"
173 " brne %[val], %[UNLOCKED], 4f \n" /* !UNLOCKED, bail */
174 " mov %[val], %[WR_LOCKED] \n"
175 " scond %[val], [%[rwlock]] \n"
176 " bnz 1b \n" /* retry if collided with someone */
177 " mov %[got_it], 1 \n"
179 "4: ; --- done --- \n"
182 [got_it] "+&r" (got_it)
183 : [rwlock] "r" (&(rw->counter)),
184 [UNLOCKED] "ir" (__ARCH_RW_LOCK_UNLOCKED__),
193 static inline void arch_read_unlock(arch_rwlock_t *rw)
202 __asm__ __volatile__(
203 "1: llock %[val], [%[rwlock]] \n"
204 " add %[val], %[val], 1 \n"
205 " scond %[val], [%[rwlock]] \n"
209 : [rwlock] "r" (&(rw->counter))
213 static inline void arch_write_unlock(arch_rwlock_t *rw)
217 WRITE_ONCE(rw->counter, __ARCH_RW_LOCK_UNLOCKED__);
220 #else /* !CONFIG_ARC_HAS_LLSC */
222 static inline void arch_spin_lock(arch_spinlock_t *lock)
224 unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
227 * Per lkmm, smp_mb() is only required after _lock (and before_unlock)
228 * for ACQ and REL semantics respectively. However EX based spinlocks
229 * need the extra smp_mb to workaround a hardware quirk.
233 __asm__ __volatile__(
235 #ifdef CONFIG_EZNPS_MTM_EXT
238 " breq %0, %2, 1b \n"
240 : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
241 #ifdef CONFIG_EZNPS_MTM_EXT
242 , "i"(CTOP_INST_SCHD_RW)
249 /* 1 - lock taken successfully */
250 static inline int arch_spin_trylock(arch_spinlock_t *lock)
252 unsigned int val = __ARCH_SPIN_LOCK_LOCKED__;
256 __asm__ __volatile__(
259 : "r"(&(lock->slock))
264 return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
267 static inline void arch_spin_unlock(arch_spinlock_t *lock)
269 unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;
272 * RELEASE barrier: given the instructions avail on ARCv2, full barrier
278 * EX is not really required here, a simple STore of 0 suffices.
279 * However this causes tasklist livelocks in SystemC based SMP virtual
280 * platforms where the systemc core scheduler uses EX as a cue for
281 * moving to next core. Do a git log of this file for details
283 __asm__ __volatile__(
286 : "r"(&(lock->slock))
290 * see pairing version/comment in arch_spin_lock above
296 * Read-write spinlocks, allowing multiple readers but only one writer.
297 * Unfair locking as Writers could be starved indefinitely by Reader(s)
299 * The spinlock itself is contained in @counter and access to it is
300 * serialized with @lock_mutex.
303 /* 1 - lock taken successfully */
304 static inline int arch_read_trylock(arch_rwlock_t *rw)
309 local_irq_save(flags);
310 arch_spin_lock(&(rw->lock_mutex));
313 * zero means writer holds the lock exclusively, deny Reader.
314 * Otherwise grant lock to first/subseq reader
316 if (rw->counter > 0) {
321 arch_spin_unlock(&(rw->lock_mutex));
322 local_irq_restore(flags);
327 /* 1 - lock taken successfully */
328 static inline int arch_write_trylock(arch_rwlock_t *rw)
333 local_irq_save(flags);
334 arch_spin_lock(&(rw->lock_mutex));
337 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
338 * deny writer. Otherwise if unlocked grant to writer
339 * Hence the claim that Linux rwlocks are unfair to writers.
340 * (can be starved for an indefinite time by readers).
342 if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
346 arch_spin_unlock(&(rw->lock_mutex));
347 local_irq_restore(flags);
352 static inline void arch_read_lock(arch_rwlock_t *rw)
354 while (!arch_read_trylock(rw))
358 static inline void arch_write_lock(arch_rwlock_t *rw)
360 while (!arch_write_trylock(rw))
364 static inline void arch_read_unlock(arch_rwlock_t *rw)
368 local_irq_save(flags);
369 arch_spin_lock(&(rw->lock_mutex));
371 arch_spin_unlock(&(rw->lock_mutex));
372 local_irq_restore(flags);
375 static inline void arch_write_unlock(arch_rwlock_t *rw)
379 local_irq_save(flags);
380 arch_spin_lock(&(rw->lock_mutex));
381 rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
382 arch_spin_unlock(&(rw->lock_mutex));
383 local_irq_restore(flags);
388 #endif /* __ASM_SPINLOCK_H */