include/asm-ppc64/semaphore.h

   1 #ifndef _PPC64_SEMAPHORE_H
   2 #define _PPC64_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 __MUTEX_INITIALIZER(name) \
  35         __SEMAPHORE_INITIALIZER(name, 1)
  36
  37 #define __DECLARE_SEMAPHORE_GENERIC(name, count) \
  38         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  39
  40 #define DECLARE_MUTEX(name)             __DECLARE_SEMAPHORE_GENERIC(name, 1)
  41 #define DECLARE_MUTEX_LOCKED(name)      __DECLARE_SEMAPHORE_GENERIC(name, 0)
  42
  43 static inline void sema_init (struct semaphore *sem, int val)
  44 {
  45         atomic_set(&sem->count, val);
  46         init_waitqueue_head(&sem->wait);
  47 }
  48
  49 static inline void init_MUTEX (struct semaphore *sem)
  50 {
  51         sema_init(sem, 1);
  52 }
  53
  54 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  55 {
  56         sema_init(sem, 0);
  57 }
  58
  59 extern void __down(struct semaphore * sem);
  60 extern int  __down_interruptible(struct semaphore * sem);
  61 extern void __up(struct semaphore * sem);
  62
  63 static inline void down(struct semaphore * sem)
  64 {
  65         might_sleep();
  66
  67         /*
  68          * Try to get the semaphore, take the slow path if we fail.
  69          */
  70         if (unlikely(atomic_dec_return(&sem->count) < 0))
  71                 __down(sem);
  72 }
  73
  74 static inline int down_interruptible(struct semaphore * sem)
  75 {
  76         int ret = 0;
  77
  78         might_sleep();
  79
  80         if (unlikely(atomic_dec_return(&sem->count) < 0))
  81                 ret = __down_interruptible(sem);
  82         return ret;
  83 }
  84
  85 static inline int down_trylock(struct semaphore * sem)
  86 {
  87         return atomic_dec_if_positive(&sem->count) < 0;
  88 }
  89
  90 static inline void up(struct semaphore * sem)
  91 {
  92         if (unlikely(atomic_inc_return(&sem->count) <= 0))
  93                 __up(sem);
  94 }
  95
  96 #endif /* __KERNEL__ */
  97
  98 #endif /* !(_PPC64_SEMAPHORE_H) */