include/asm-sh/semaphore-helper.h

   1 #ifndef __ASM_SH_SEMAPHORE_HELPER_H
   2 #define __ASM_SH_SEMAPHORE_HELPER_H
   3
   4 /*
   5  * SMP- and interrupt-safe semaphores helper functions.
   6  *
   7  * (C) Copyright 1996 Linus Torvalds
   8  * (C) Copyright 1999 Andrea Arcangeli
   9  */
  10
  11 /*
  12  * These two _must_ execute atomically wrt each other.
  13  *
  14  * This is trivially done with load_locked/store_cond,
  15  * which we have.  Let the rest of the losers suck eggs.
  16  */
  17 static __inline__ void wake_one_more(struct semaphore * sem)
  18 {
  19         atomic_inc((atomic_t *)&sem->sleepers);
  20 }
  21
  22 static __inline__ int waking_non_zero(struct semaphore *sem)
  23 {
  24         unsigned long flags;
  25         int ret = 0;
  26
  27         spin_lock_irqsave(&semaphore_wake_lock, flags);
  28         if (sem->sleepers > 0) {
  29                 sem->sleepers--;
  30                 ret = 1;
  31         }
  32         spin_unlock_irqrestore(&semaphore_wake_lock, flags);
  33         return ret;
  34 }
  35
  36 /*
  37  * waking_non_zero_interruptible:
  38  *      1       got the lock
  39  *      0       go to sleep
  40  *      -EINTR  interrupted
  41  *
  42  * We must undo the sem->count down_interruptible() increment while we are
  43  * protected by the spinlock in order to make atomic this atomic_inc() with the
  44  * atomic_read() in wake_one_more(), otherwise we can race. -arca
  45  */
  46 static __inline__ int waking_non_zero_interruptible(struct semaphore *sem,
  47                                                 struct task_struct *tsk)
  48 {
  49         unsigned long flags;
  50         int ret = 0;
  51
  52         spin_lock_irqsave(&semaphore_wake_lock, flags);
  53         if (sem->sleepers > 0) {
  54                 sem->sleepers--;
  55                 ret = 1;
  56         } else if (signal_pending(tsk)) {
  57                 atomic_inc(&sem->count);
  58                 ret = -EINTR;
  59         }
  60         spin_unlock_irqrestore(&semaphore_wake_lock, flags);
  61         return ret;
  62 }
  63
  64 /*
  65  * waking_non_zero_trylock:
  66  *      1       failed to lock
  67  *      0       got the lock
  68  *
  69  * We must undo the sem->count down_trylock() increment while we are
  70  * protected by the spinlock in order to make atomic this atomic_inc() with the
  71  * atomic_read() in wake_one_more(), otherwise we can race. -arca
  72  */
  73 static __inline__ int waking_non_zero_trylock(struct semaphore *sem)
  74 {
  75         unsigned long flags;
  76         int ret = 1;
  77
  78         spin_lock_irqsave(&semaphore_wake_lock, flags);
  79         if (sem->sleepers <= 0)
  80                 atomic_inc(&sem->count);
  81         else {
  82                 sem->sleepers--;
  83                 ret = 0;
  84         }
  85         spin_unlock_irqrestore(&semaphore_wake_lock, flags);
  86         return ret;
  87 }
  88
  89 #endif /* __ASM_SH_SEMAPHORE_HELPER_H */