include/asm-ppc/semaphore-helper.h

   1 #ifndef _PPC_SEMAPHORE_HELPER_H
   2 #define _PPC_SEMAPHORE_HELPER_H
   3
   4 /*
   5  * SMP- and interrupt-safe semaphores..
   6  *
   7  * (C) Copyright 1996 Linus Torvalds
   8  * Adapted for PowerPC by Gary Thomas and Paul Mackerras
   9  */
  10
  11 #include <asm/atomic.h>
  12
  13 /*
  14  * These two (wake_one_more and waking_non_zero) _must_ execute
  15  * atomically wrt each other.
  16  *
  17  * This is trivially done with load with reservation and
  18  * store conditional on the ppc.
  19  */
  20
  21 static inline void wake_one_more(struct semaphore * sem)
  22 {
  23         atomic_inc(&sem->waking);
  24 }
  25
  26 static inline int waking_non_zero(struct semaphore *sem)
  27 {
  28         int ret, tmp;
  29
  30         /* Atomic decrement sem->waking iff it is > 0 */
  31         __asm__ __volatile__(
  32                 "1:     lwarx %1,0,%2\n"        /* tmp = sem->waking */
  33                 "       cmpwi 0,%1,0\n"         /* test tmp */
  34                 "       addic %1,%1,-1\n"       /* --tmp */
  35                 "       ble- 2f\n"              /* exit if tmp was <= 0 */
  36                 "       stwcx. %1,0,%2\n"       /* update sem->waking */
  37                 "       bne- 1b\n"              /* try again if update failed*/
  38                 "       li %0,1\n"              /* ret = 1 */
  39                 "2:"
  40                 : "=r" (ret), "=&r" (tmp)
  41                 : "r" (&sem->waking), "0" (0)
  42                 : "cr0", "memory");
  43
  44         return ret;
  45 }
  46 /*
  47  * waking_non_zero_interruptible:
  48  *      1       got the lock
  49  *      0       go to sleep
  50  *      -EINTR  interrupted
  51  */
  52 static inline int waking_non_zero_interruptible(struct semaphore *sem,
  53                                                 struct task_struct *tsk)
  54 {
  55         int ret, tmp;
  56
  57         /* Atomic decrement sem->waking iff it is > 0 */
  58         __asm__ __volatile__(
  59                 "1:     lwarx %1,0,%2\n"        /* tmp = sem->waking */
  60                 "       cmpwi 0,%1,0\n"         /* test tmp */
  61                 "       addic %1,%1,-1\n"       /* --tmp */
  62                 "       ble- 2f\n"              /* exit if tmp was <= 0 */
  63                 "       stwcx. %1,0,%2\n"       /* update sem->waking */
  64                 "       bne- 1b\n"              /* try again if update failed*/
  65                 "       li %0,1\n"              /* ret = 1 */
  66                 "2:"
  67                 : "=r" (ret), "=&r" (tmp)
  68                 : "r" (&sem->waking), "0" (0)
  69                 : "cr0", "memory");
  70
  71         if (ret == 0 && signal_pending(tsk)) {
  72                 atomic_inc(&sem->count);
  73                 ret = -EINTR;
  74         }
  75         return ret;
  76 }
  77
  78 /*
  79  * waking_non_zero_trylock:
  80  *      1       failed to lock
  81  *      0       got the lock
  82  */
  83 static inline int waking_non_zero_trylock(struct semaphore *sem)
  84 {
  85         int ret, tmp;
  86
  87         /* Atomic decrement sem->waking iff it is > 0 */
  88         __asm__ __volatile__(
  89                 "1:     lwarx %1,0,%2\n"        /* tmp = sem->waking */
  90                 "       cmpwi 0,%1,0\n"         /* test tmp */
  91                 "       addic %1,%1,-1\n"       /* --tmp */
  92                 "       ble- 2f\n"              /* exit if tmp was <= 0 */
  93                 "       stwcx. %1,0,%2\n"       /* update sem->waking */
  94                 "       bne- 1b\n"              /* try again if update failed*/
  95                 "       li %0,0\n"              /* ret = 0 */
  96                 "2:"
  97                 : "=r" (ret), "=&r" (tmp)
  98                 : "r" (&sem->waking), "0" (1)
  99                 : "cr0", "memory");
 100
 101         if (ret)
 102                 atomic_inc(&sem->count);
 103
 104         return ret;
 105 }
 106
 107 #endif /* _PPC_SEMAPHORE_HELPER_H */