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#ifndef ARCH_SMP_SPINLOCK_H
#define ARCH_SMP_SPINLOCK_H
/*
* Your basic SMP spinlocks, allowing only a single CPU anywhere
*/
typedef struct {
volatile unsigned int lock;
} spinlock_t;
#define SPIN_LOCK_UNLOCKED (spinlock_t) { 1 }
#define DECLARE_SPIN_LOCK(x) static spinlock_t x = SPIN_LOCK_UNLOCKED;
/*
* 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.
*/
#define barrier() __asm__ __volatile__("": : :"memory")
#define spin_is_locked(x) (*(volatile char *)(&(x)->lock) <= 0)
#define spin_unlock_wait(x) do { barrier(); } while(spin_is_locked(x))
#define spin_lock_string \
"\n1:\t" \
"lock ; decb %0\n\t" \
"js 2f\n" \
".section .text.lock,\"ax\"\n" \
"2:\t" \
"cmpb $0,%0\n\t" \
"rep;nop\n\t" \
"jle 2b\n\t" \
"jmp 1b\n" \
".previous"
/*
* This works. Despite all the confusion.
*/
#define spin_unlock_string \
"movb $1,%0"
static inline __attribute__((always_inline)) void spin_lock(spinlock_t *lock)
{
__asm__ __volatile__(
spin_lock_string
:"=m" (lock->lock) : : "memory");
}
static inline __attribute__((always_inline)) void spin_unlock(spinlock_t *lock)
{
__asm__ __volatile__(
spin_unlock_string
:"=m" (lock->lock) : : "memory");
}
/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
static inline __attribute__((always_inline)) void cpu_relax(void)
{
__asm__ __volatile__("rep;nop": : :"memory");
}
#endif /* ARCH_SMP_SPINLOCK_H */
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