3 * Copyright IBM Corp. 1999
4 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
6 * Derived from "include/asm-i386/spinlock.h"
9 #ifndef __ASM_SPINLOCK_H
10 #define __ASM_SPINLOCK_H
12 #include <linux/smp.h>
14 extern int spin_retry;
17 _raw_compare_and_swap(volatile unsigned int *lock,
18 unsigned int old, unsigned int new)
22 : "=d" (old), "=Q" (*lock)
23 : "0" (old), "d" (new), "Q" (*lock)
29 * Simple spin lock operations. There are two variants, one clears IRQ's
30 * on the local processor, one does not.
32 * We make no fairness assumptions. They have a cost.
34 * (the type definitions are in asm/spinlock_types.h)
37 #define arch_spin_is_locked(x) ((x)->owner_cpu != 0)
38 #define arch_spin_unlock_wait(lock) \
39 do { while (arch_spin_is_locked(lock)) \
40 arch_spin_relax(lock); } while (0)
42 extern void arch_spin_lock_wait(arch_spinlock_t *);
43 extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
44 extern int arch_spin_trylock_retry(arch_spinlock_t *);
45 extern void arch_spin_relax(arch_spinlock_t *lock);
47 static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
49 return lock.owner_cpu == 0;
52 static inline void arch_spin_lock(arch_spinlock_t *lp)
56 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
59 arch_spin_lock_wait(lp);
62 static inline void arch_spin_lock_flags(arch_spinlock_t *lp,
67 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
70 arch_spin_lock_wait_flags(lp, flags);
73 static inline int arch_spin_trylock(arch_spinlock_t *lp)
77 old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
80 return arch_spin_trylock_retry(lp);
83 static inline void arch_spin_unlock(arch_spinlock_t *lp)
85 _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0);
89 * Read-write spinlocks, allowing multiple readers
90 * but only one writer.
92 * NOTE! it is quite common to have readers in interrupts
93 * but no interrupt writers. For those circumstances we
94 * can "mix" irq-safe locks - any writer needs to get a
95 * irq-safe write-lock, but readers can get non-irqsafe
100 * read_can_lock - would read_trylock() succeed?
101 * @lock: the rwlock in question.
103 #define arch_read_can_lock(x) ((int)(x)->lock >= 0)
106 * write_can_lock - would write_trylock() succeed?
107 * @lock: the rwlock in question.
109 #define arch_write_can_lock(x) ((x)->lock == 0)
111 extern void _raw_read_lock_wait(arch_rwlock_t *lp);
112 extern void _raw_read_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags);
113 extern int _raw_read_trylock_retry(arch_rwlock_t *lp);
114 extern void _raw_write_lock_wait(arch_rwlock_t *lp);
115 extern void _raw_write_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags);
116 extern int _raw_write_trylock_retry(arch_rwlock_t *lp);
118 static inline void arch_read_lock(arch_rwlock_t *rw)
121 old = rw->lock & 0x7fffffffU;
122 if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
123 _raw_read_lock_wait(rw);
126 static inline void arch_read_lock_flags(arch_rwlock_t *rw, unsigned long flags)
129 old = rw->lock & 0x7fffffffU;
130 if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
131 _raw_read_lock_wait_flags(rw, flags);
134 static inline void arch_read_unlock(arch_rwlock_t *rw)
136 unsigned int old, cmp;
141 old = _raw_compare_and_swap(&rw->lock, old, old - 1);
142 } while (cmp != old);
145 static inline void arch_write_lock(arch_rwlock_t *rw)
147 if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
148 _raw_write_lock_wait(rw);
151 static inline void arch_write_lock_flags(arch_rwlock_t *rw, unsigned long flags)
153 if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
154 _raw_write_lock_wait_flags(rw, flags);
157 static inline void arch_write_unlock(arch_rwlock_t *rw)
159 _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
162 static inline int arch_read_trylock(arch_rwlock_t *rw)
165 old = rw->lock & 0x7fffffffU;
166 if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
168 return _raw_read_trylock_retry(rw);
171 static inline int arch_write_trylock(arch_rwlock_t *rw)
173 if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
175 return _raw_write_trylock_retry(rw);
178 #define arch_read_relax(lock) cpu_relax()
179 #define arch_write_relax(lock) cpu_relax()
181 #endif /* __ASM_SPINLOCK_H */