include/asm-powerpc/semaphore.h

   1 #ifndef _ASM_POWERPC_SEMAPHORE_H
   2 #define _ASM_POWERPC_SEMAPHORE_H
   3
   4 /*
   5  * Remove spinlock-based RW semaphores; RW semaphore definitions are
   6  * now in rwsem.h and we use the generic lib/rwsem.c implementation.
   7  * Rework semaphores to use atomic_dec_if_positive.
   8  * -- Paul Mackerras (paulus@samba.org)
   9  */
  10
  11 #ifdef __KERNEL__
  12
  13 #include <asm/atomic.h>
  14 #include <asm/system.h>
  15 #include <linux/wait.h>
  16 #include <linux/rwsem.h>
  17
  18 struct semaphore {
  19         /*
  20          * Note that any negative value of count is equivalent to 0,
  21          * but additionally indicates that some process(es) might be
  22          * sleeping on `wait'.
  23          */
  24         atomic_t count;
  25         wait_queue_head_t wait;
  26 };
  27
  28 #define __SEMAPHORE_INITIALIZER(name, n)                                \
  29 {                                                                       \
  30         .count          = ATOMIC_INIT(n),                               \
  31         .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  32 }
  33
  34 #define __DECLARE_SEMAPHORE_GENERIC(name, count) \
  35         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  36
  37 #define DECLARE_MUTEX(name)             __DECLARE_SEMAPHORE_GENERIC(name, 1)
  38
  39 static inline void sema_init (struct semaphore *sem, int val)
  40 {
  41         atomic_set(&sem->count, val);
  42         init_waitqueue_head(&sem->wait);
  43 }
  44
  45 static inline void init_MUTEX (struct semaphore *sem)
  46 {
  47         sema_init(sem, 1);
  48 }
  49
  50 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  51 {
  52         sema_init(sem, 0);
  53 }
  54
  55 extern void __down(struct semaphore * sem);
  56 extern int  __down_interruptible(struct semaphore * sem);
  57 extern void __up(struct semaphore * sem);
  58
  59 static inline void down(struct semaphore * sem)
  60 {
  61         might_sleep();
  62
  63         /*
  64          * Try to get the semaphore, take the slow path if we fail.
  65          */
  66         if (unlikely(atomic_dec_return(&sem->count) < 0))
  67                 __down(sem);
  68 }
  69
  70 static inline int down_interruptible(struct semaphore * sem)
  71 {
  72         int ret = 0;
  73
  74         might_sleep();
  75
  76         if (unlikely(atomic_dec_return(&sem->count) < 0))
  77                 ret = __down_interruptible(sem);
  78         return ret;
  79 }
  80
  81 static inline int down_trylock(struct semaphore * sem)
  82 {
  83         return atomic_dec_if_positive(&sem->count) < 0;
  84 }
  85
  86 static inline void up(struct semaphore * sem)
  87 {
  88         if (unlikely(atomic_inc_return(&sem->count) <= 0))
  89                 __up(sem);
  90 }
  91
  92 #endif /* __KERNEL__ */
  93
  94 #endif /* _ASM_POWERPC_SEMAPHORE_H */