2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
9 #ifndef __ASM_SPINLOCK_H
10 #define __ASM_SPINLOCK_H
12 #include <asm/spinlock_types.h>
13 #include <asm/processor.h>
14 #include <asm/barrier.h>
16 #define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
17 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
18 #define arch_spin_unlock_wait(x) \
19 do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
21 static inline void arch_spin_lock(arch_spinlock_t *lock)
23 unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
29 : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
33 static inline int arch_spin_trylock(arch_spinlock_t *lock)
35 unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
43 return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
46 static inline void arch_spin_unlock(arch_spinlock_t *lock)
48 unsigned int tmp = __ARCH_SPIN_LOCK_UNLOCKED__;
60 * Read-write spinlocks, allowing multiple readers but only one writer.
62 * The spinlock itself is contained in @counter and access to it is
63 * serialized with @lock_mutex.
65 * Unfair locking as Writers could be starved indefinitely by Reader(s)
68 /* Would read_trylock() succeed? */
69 #define arch_read_can_lock(x) ((x)->counter > 0)
71 /* Would write_trylock() succeed? */
72 #define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
74 /* 1 - lock taken successfully */
75 static inline int arch_read_trylock(arch_rwlock_t *rw)
79 arch_spin_lock(&(rw->lock_mutex));
82 * zero means writer holds the lock exclusively, deny Reader.
83 * Otherwise grant lock to first/subseq reader
85 if (rw->counter > 0) {
90 arch_spin_unlock(&(rw->lock_mutex));
96 /* 1 - lock taken successfully */
97 static inline int arch_write_trylock(arch_rwlock_t *rw)
101 arch_spin_lock(&(rw->lock_mutex));
104 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
105 * deny writer. Otherwise if unlocked grant to writer
106 * Hence the claim that Linux rwlocks are unfair to writers.
107 * (can be starved for an indefinite time by readers).
109 if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
113 arch_spin_unlock(&(rw->lock_mutex));
118 static inline void arch_read_lock(arch_rwlock_t *rw)
120 while (!arch_read_trylock(rw))
124 static inline void arch_write_lock(arch_rwlock_t *rw)
126 while (!arch_write_trylock(rw))
130 static inline void arch_read_unlock(arch_rwlock_t *rw)
132 arch_spin_lock(&(rw->lock_mutex));
134 arch_spin_unlock(&(rw->lock_mutex));
137 static inline void arch_write_unlock(arch_rwlock_t *rw)
139 arch_spin_lock(&(rw->lock_mutex));
140 rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
141 arch_spin_unlock(&(rw->lock_mutex));
144 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
145 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
147 #define arch_spin_relax(lock) cpu_relax()
148 #define arch_read_relax(lock) cpu_relax()
149 #define arch_write_relax(lock) cpu_relax()
151 #endif /* __ASM_SPINLOCK_H */