2bd0cfbde2
We need processor.h for cpu_relax(). Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
137 lines
3.1 KiB
C
137 lines
3.1 KiB
C
#ifndef __ASM_SPINLOCK_H
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#define __ASM_SPINLOCK_H
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#include <asm/atomic.h>
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#include <asm/rwlock.h>
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#include <asm/page.h>
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#include <asm/processor.h>
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/*
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* Your basic SMP spinlocks, allowing only a single CPU anywhere
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*
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* Simple spin lock operations. There are two variants, one clears IRQ's
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* on the local processor, one does not.
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*
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* We make no fairness assumptions. They have a cost.
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*
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* (the type definitions are in asm/spinlock_types.h)
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*/
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static inline int __raw_spin_is_locked(raw_spinlock_t *lock)
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{
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return *(volatile signed int *)(&(lock)->slock) <= 0;
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}
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static inline void __raw_spin_lock(raw_spinlock_t *lock)
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{
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asm volatile(
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"\n1:\t"
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LOCK_PREFIX " ; decl %0\n\t"
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"jns 2f\n"
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"3:\n"
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"rep;nop\n\t"
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"cmpl $0,%0\n\t"
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"jle 3b\n\t"
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"jmp 1b\n"
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"2:\t" : "=m" (lock->slock) : : "memory");
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}
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#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
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static inline int __raw_spin_trylock(raw_spinlock_t *lock)
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{
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int oldval;
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asm volatile(
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"xchgl %0,%1"
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:"=q" (oldval), "=m" (lock->slock)
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:"0" (0) : "memory");
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return oldval > 0;
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}
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static inline void __raw_spin_unlock(raw_spinlock_t *lock)
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{
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asm volatile("movl $1,%0" :"=m" (lock->slock) :: "memory");
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}
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static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
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{
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while (__raw_spin_is_locked(lock))
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cpu_relax();
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}
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/*
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* Read-write spinlocks, allowing multiple readers
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* but only one writer.
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*
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* NOTE! it is quite common to have readers in interrupts
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* but no interrupt writers. For those circumstances we
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* can "mix" irq-safe locks - any writer needs to get a
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* irq-safe write-lock, but readers can get non-irqsafe
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* read-locks.
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*
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* On x86, we implement read-write locks as a 32-bit counter
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* with the high bit (sign) being the "contended" bit.
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*/
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static inline int __raw_read_can_lock(raw_rwlock_t *lock)
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{
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return (int)(lock)->lock > 0;
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}
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static inline int __raw_write_can_lock(raw_rwlock_t *lock)
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{
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return (lock)->lock == RW_LOCK_BIAS;
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}
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static inline void __raw_read_lock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t"
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"jns 1f\n"
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"call __read_lock_failed\n"
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"1:\n"
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::"D" (rw), "i" (RW_LOCK_BIAS) : "memory");
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}
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static inline void __raw_write_lock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX "subl %1,(%0)\n\t"
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"jz 1f\n"
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"\tcall __write_lock_failed\n\t"
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"1:\n"
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::"D" (rw), "i" (RW_LOCK_BIAS) : "memory");
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}
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static inline int __raw_read_trylock(raw_rwlock_t *lock)
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{
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atomic_t *count = (atomic_t *)lock;
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atomic_dec(count);
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if (atomic_read(count) >= 0)
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return 1;
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atomic_inc(count);
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return 0;
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}
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static inline int __raw_write_trylock(raw_rwlock_t *lock)
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{
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atomic_t *count = (atomic_t *)lock;
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if (atomic_sub_and_test(RW_LOCK_BIAS, count))
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return 1;
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atomic_add(RW_LOCK_BIAS, count);
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return 0;
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}
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static inline void __raw_read_unlock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX " ; incl %0" :"=m" (rw->lock) : : "memory");
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}
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static inline void __raw_write_unlock(raw_rwlock_t *rw)
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{
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asm volatile(LOCK_PREFIX " ; addl $" RW_LOCK_BIAS_STR ",%0"
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: "=m" (rw->lock) : : "memory");
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}
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#endif /* __ASM_SPINLOCK_H */
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