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include/asm-parisc/semaphore-helper.h 2.1 KB
1da177e4c   Linus Torvalds   Linux-2.6.12-rc2
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  #ifndef _ASM_PARISC_SEMAPHORE_HELPER_H
  #define _ASM_PARISC_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->waking);
  }
  
  static __inline__ int waking_non_zero(struct semaphore *sem)
  {
  	unsigned long flags;
  	int ret = 0;
  
  	spin_lock_irqsave(&semaphore_wake_lock, flags);
  	if (sem->waking > 0) {
  		sem->waking--;
  		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->waking > 0) {
  		sem->waking--;
  		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->waking <= 0)
  		atomic_inc(&sem->count);
  	else {
  		sem->waking--;
  		ret = 0;
  	}
  	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
  	return ret;
  }
  
  #endif /* _ASM_PARISC_SEMAPHORE_HELPER_H */