include/asm-ppc/semaphore.h

   1 #ifndef _PPC_SEMAPHORE_H
   2 #define _PPC_SEMAPHORE_H
   3
   4 /*
   5  * Swiped from asm-sparc/semaphore.h and modified
   6  * -- Cort (cort@cs.nmt.edu)
   7  *
   8  * Stole some rw spinlock-based semaphore stuff from asm-alpha/semaphore.h
   9  * -- Ani Joshi (ajoshi@unixbox.com)
  10  *
  11  * Remove spinlock-based RW semaphores; RW semaphore definitions are
  12  * now in rwsem.h and we use the generic lib/rwsem.c implementation.
  13  * Rework semaphores to use atomic_dec_if_positive.
  14  * -- Paul Mackerras (paulus@samba.org)
  15  */
  16
  17 #ifdef __KERNEL__
  18
  19 #include <asm/atomic.h>
  20 #include <asm/system.h>
  21 #include <linux/wait.h>
  22 #include <linux/rwsem.h>
  23
  24 struct semaphore {
  25         /*
  26          * Note that any negative value of count is equivalent to 0,
  27          * but additionally indicates that some process(es) might be
  28          * sleeping on `wait'.
  29          */
  30         atomic_t count;
  31         wait_queue_head_t wait;
  32 };
  33
  34 #define __SEMAPHORE_INITIALIZER(name, n)                                \
  35 {                                                                       \
  36         .count          = ATOMIC_INIT(n),                               \
  37         .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  38 }
  39
  40 #define __MUTEX_INITIALIZER(name) \
  41         __SEMAPHORE_INITIALIZER(name, 1)
  42
  43 #define __DECLARE_SEMAPHORE_GENERIC(name, count) \
  44         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  45
  46 #define DECLARE_MUTEX(name)             __DECLARE_SEMAPHORE_GENERIC(name, 1)
  47 #define DECLARE_MUTEX_LOCKED(name)      __DECLARE_SEMAPHORE_GENERIC(name, 0)
  48
  49 static inline void sema_init (struct semaphore *sem, int val)
  50 {
  51         atomic_set(&sem->count, val);
  52         init_waitqueue_head(&sem->wait);
  53 }
  54
  55 static inline void init_MUTEX (struct semaphore *sem)
  56 {
  57         sema_init(sem, 1);
  58 }
  59
  60 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  61 {
  62         sema_init(sem, 0);
  63 }
  64
  65 extern void __down(struct semaphore * sem);
  66 extern int  __down_interruptible(struct semaphore * sem);
  67 extern void __up(struct semaphore * sem);
  68
  69 extern inline void down(struct semaphore * sem)
  70 {
  71         might_sleep();
  72
  73         /*
  74          * Try to get the semaphore, take the slow path if we fail.
  75          */
  76         if (atomic_dec_return(&sem->count) < 0)
  77                 __down(sem);
  78         smp_wmb();
  79 }
  80
  81 extern inline int down_interruptible(struct semaphore * sem)
  82 {
  83         int ret = 0;
  84
  85         might_sleep();
  86
  87         if (atomic_dec_return(&sem->count) < 0)
  88                 ret = __down_interruptible(sem);
  89         smp_wmb();
  90         return ret;
  91 }
  92
  93 extern inline int down_trylock(struct semaphore * sem)
  94 {
  95         int ret;
  96
  97         ret = atomic_dec_if_positive(&sem->count) < 0;
  98         smp_wmb();
  99         return ret;
 100 }
 101
 102 extern inline void up(struct semaphore * sem)
 103 {
 104         smp_wmb();
 105         if (atomic_inc_return(&sem->count) <= 0)
 106                 __up(sem);
 107 }
 108
 109 #endif /* __KERNEL__ */
 110
 111 #endif /* !(_PPC_SEMAPHORE_H) */