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 #define DECLARE_MUTEX_LOCKED(name)      __DECLARE_SEMAPHORE_GENERIC(name, 0)
  39
  40 static inline void sema_init (struct semaphore *sem, int val)
  41 {
  42         atomic_set(&sem->count, val);
  43         init_waitqueue_head(&sem->wait);
  44 }
  45
  46 static inline void init_MUTEX (struct semaphore *sem)
  47 {
  48         sema_init(sem, 1);
  49 }
  50
  51 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  52 {
  53         sema_init(sem, 0);
  54 }
  55
  56 extern void __down(struct semaphore * sem);
  57 extern int  __down_interruptible(struct semaphore * sem);
  58 extern void __up(struct semaphore * sem);
  59
  60 static inline void down(struct semaphore * sem)
  61 {
  62         might_sleep();
  63
  64         /*
  65          * Try to get the semaphore, take the slow path if we fail.
  66          */
  67         if (unlikely(atomic_dec_return(&sem->count) < 0))
  68                 __down(sem);
  69 }
  70
  71 static inline int down_interruptible(struct semaphore * sem)
  72 {
  73         int ret = 0;
  74
  75         might_sleep();
  76
  77         if (unlikely(atomic_dec_return(&sem->count) < 0))
  78                 ret = __down_interruptible(sem);
  79         return ret;
  80 }
  81
  82 static inline int down_trylock(struct semaphore * sem)
  83 {
  84         return atomic_dec_if_positive(&sem->count) < 0;
  85 }
  86
  87 static inline void up(struct semaphore * sem)
  88 {
  89         if (unlikely(atomic_inc_return(&sem->count) <= 0))
  90                 __up(sem);
  91 }
  92
  93 #endif /* __KERNEL__ */
  94
  95 #endif /* _ASM_POWERPC_SEMAPHORE_H */