semaphore-helper.h
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#ifndef __ASM_SH_SEMAPHORE_HELPER_H
#define __ASM_SH_SEMAPHORE_HELPER_H
/*
* SMP- and interrupt-safe semaphores helper functions.
*
* (C) Copyright 1996 Linus Torvalds
* (C) Copyright 1999 Andrea Arcangeli
*/
/*
* These two _must_ execute atomically wrt each other.
*
* This is trivially done with load_locked/store_cond,
* which we have. Let the rest of the losers suck eggs.
*/
static __inline__ void wake_one_more(struct semaphore * sem)
{
atomic_inc((atomic_t *)&sem->sleepers);
}
static __inline__ int waking_non_zero(struct semaphore *sem)
{
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&semaphore_wake_lock, flags);
if (sem->sleepers > 0) {
sem->sleepers--;
ret = 1;
}
spin_unlock_irqrestore(&semaphore_wake_lock, flags);
return ret;
}
/*
* waking_non_zero_interruptible:
* 1 got the lock
* 0 go to sleep
* -EINTR interrupted
*
* We must undo the sem->count down_interruptible() increment while we are
* protected by the spinlock in order to make atomic this atomic_inc() with the
* atomic_read() in wake_one_more(), otherwise we can race. -arca
*/
static __inline__ int waking_non_zero_interruptible(struct semaphore *sem,
struct task_struct *tsk)
{
unsigned long flags;
int ret = 0;
spin_lock_irqsave(&semaphore_wake_lock, flags);
if (sem->sleepers > 0) {
sem->sleepers--;
ret = 1;
} else if (signal_pending(tsk)) {
atomic_inc(&sem->count);
ret = -EINTR;
}
spin_unlock_irqrestore(&semaphore_wake_lock, flags);
return ret;
}
/*
* waking_non_zero_trylock:
* 1 failed to lock
* 0 got the lock
*
* We must undo the sem->count down_trylock() increment while we are
* protected by the spinlock in order to make atomic this atomic_inc() with the
* atomic_read() in wake_one_more(), otherwise we can race. -arca
*/
static __inline__ int waking_non_zero_trylock(struct semaphore *sem)
{
unsigned long flags;
int ret = 1;
spin_lock_irqsave(&semaphore_wake_lock, flags);
if (sem->sleepers <= 0)
atomic_inc(&sem->count);
else {
sem->sleepers--;
ret = 0;
}
spin_unlock_irqrestore(&semaphore_wake_lock, flags);
return ret;
}
#endif /* __ASM_SH_SEMAPHORE_HELPER_H */