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#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#include <asm/atomic.h>
#include <asm/rwlock.h>
#include <asm/page.h>
/*
* Your basic SMP spinlocks, allowing only a single CPU anywhere
*
* Simple spin lock operations. There are two variants, one clears IRQ's
* on the local processor, one does not.
*
* We make no fairness assumptions. They have a cost.
*
* (the type definitions are in asm/spinlock_types.h)
*/
#define __raw_spin_is_locked(x) \
(*(volatile signed int *)(&(x)->slock) <= 0)
#define __raw_spin_lock_string \
"\n1:\t" \
LOCK_PREFIX " ; decl %0\n\t" \
"js 2f\n" \
LOCK_SECTION_START("") \
"2:\t" \
"rep;nop\n\t" \
"cmpl $0,%0\n\t" \
"jle 2b\n\t" \
"jmp 1b\n" \
LOCK_SECTION_END
#define __raw_spin_lock_string_up \
"\n\tdecl %0"
#define __raw_spin_unlock_string \
"movl $1,%0" \
:"=m" (lock->slock) : : "memory"
static inline void __raw_spin_lock(raw_spinlock_t *lock)
{
asm volatile(__raw_spin_lock_string : "=m" (lock->slock) : : "memory");
}
#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
static inline int __raw_spin_trylock(raw_spinlock_t *lock)
{
int oldval;
__asm__ __volatile__(
"xchgl %0,%1"
:"=q" (oldval), "=m" (lock->slock)
:"0" (0) : "memory");
return oldval > 0;
}
static inline void __raw_spin_unlock(raw_spinlock_t *lock)
{
__asm__ __volatile__(
__raw_spin_unlock_string
);
}
#define __raw_spin_unlock_wait(lock) \
do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
/*
* Read-write spinlocks, allowing multiple readers
* but only one writer.
*
* NOTE! it is quite common to have readers in interrupts
* but no interrupt writers. For those circumstances we
* can "mix" irq-safe locks - any writer needs to get a
* irq-safe write-lock, but readers can get non-irqsafe
* read-locks.
*
* On x86, we implement read-write locks as a 32-bit counter
* with the high bit (sign) being the "contended" bit.
*
* The inline assembly is non-obvious. Think about it.
*
* Changed to use the same technique as rw semaphores. See
* semaphore.h for details. -ben
*
* the helpers are in arch/i386/kernel/semaphore.c
*/
#define __raw_read_can_lock(x) ((int)(x)->lock > 0)
#define __raw_write_can_lock(x) ((x)->lock == RW_LOCK_BIAS)
static inline void __raw_read_lock(raw_rwlock_t *rw)
{
__build_read_lock(rw, "__read_lock_failed");
}
static inline void __raw_write_lock(raw_rwlock_t *rw)
{
__build_write_lock(rw, "__write_lock_failed");
}
static inline int __raw_read_trylock(raw_rwlock_t *lock)
{
atomic_t *count = (atomic_t *)lock;
atomic_dec(count);
if (atomic_read(count) >= 0)
return 1;
atomic_inc(count);
return 0;
}
static inline int __raw_write_trylock(raw_rwlock_t *lock)
{
atomic_t *count = (atomic_t *)lock;
if (atomic_sub_and_test(RW_LOCK_BIAS, count))
return 1;
atomic_add(RW_LOCK_BIAS, count);
return 0;
}
static inline void __raw_read_unlock(raw_rwlock_t *rw)
{
asm volatile(LOCK_PREFIX " ; incl %0" :"=m" (rw->lock) : : "memory");
}
static inline void __raw_write_unlock(raw_rwlock_t *rw)
{
asm volatile(LOCK_PREFIX " ; addl $" RW_LOCK_BIAS_STR ",%0"
: "=m" (rw->lock) : : "memory");
}
#endif /* __ASM_SPINLOCK_H */
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