include/asm-alpha/semaphore.h

   1 #ifndef _ALPHA_SEMAPHORE_H
   2 #define _ALPHA_SEMAPHORE_H
   3
   4 /*
   5  * SMP- and interrupt-safe semaphores..
   6  *
   7  * (C) Copyright 1996 Linus Torvalds
   8  * (C) Copyright 1996, 2000 Richard Henderson
   9  */
  10
  11 #include <asm/current.h>
  12 #include <asm/system.h>
  13 #include <asm/atomic.h>
  14 #include <linux/compiler.h>
  15 #include <linux/wait.h>
  16 #include <linux/rwsem.h>
  17
  18 struct semaphore {
  19         atomic_t count;
  20         wait_queue_head_t wait;
  21 };
  22
  23 #define __SEMAPHORE_INITIALIZER(name, n)                        \
  24 {                                                               \
  25         .count  = ATOMIC_INIT(n),                               \
  26         .wait   = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait),   \
  27 }
  28
  29 #define __DECLARE_SEMAPHORE_GENERIC(name,count)         \
  30         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  31
  32 #define DECLARE_MUTEX(name)             __DECLARE_SEMAPHORE_GENERIC(name,1)
  33
  34 static inline void sema_init(struct semaphore *sem, int val)
  35 {
  36         /*
  37          * Logically,
  38          *   *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
  39          * except that gcc produces better initializing by parts yet.
  40          */
  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 *);
  57 extern void __down_failed(struct semaphore *);
  58 extern int  down_interruptible(struct semaphore *);
  59 extern int  __down_failed_interruptible(struct semaphore *);
  60 extern int  down_trylock(struct semaphore *);
  61 extern void up(struct semaphore *);
  62 extern void __up_wakeup(struct semaphore *);
  63
  64 /*
  65  * Hidden out of line code is fun, but extremely messy.  Rely on newer
  66  * compilers to do a respectable job with this.  The contention cases
  67  * are handled out of line in arch/alpha/kernel/semaphore.c.
  68  */
  69
  70 static inline void __down(struct semaphore *sem)
  71 {
  72         long count;
  73         might_sleep();
  74         count = atomic_dec_return(&sem->count);
  75         if (unlikely(count < 0))
  76                 __down_failed(sem);
  77 }
  78
  79 static inline int __down_interruptible(struct semaphore *sem)
  80 {
  81         long count;
  82         might_sleep();
  83         count = atomic_dec_return(&sem->count);
  84         if (unlikely(count < 0))
  85                 return __down_failed_interruptible(sem);
  86         return 0;
  87 }
  88
  89 /*
  90  * down_trylock returns 0 on success, 1 if we failed to get the lock.
  91  */
  92
  93 static inline int __down_trylock(struct semaphore *sem)
  94 {
  95         long ret;
  96
  97         /* "Equivalent" C:
  98
  99            do {
 100                 ret = ldl_l;
 101                 --ret;
 102                 if (ret < 0)
 103                         break;
 104                 ret = stl_c = ret;
 105            } while (ret == 0);
 106         */
 107         __asm__ __volatile__(
 108                 "1:     ldl_l   %0,%1\n"
 109                 "       subl    %0,1,%0\n"
 110                 "       blt     %0,2f\n"
 111                 "       stl_c   %0,%1\n"
 112                 "       beq     %0,3f\n"
 113                 "       mb\n"
 114                 "2:\n"
 115                 ".subsection 2\n"
 116                 "3:     br      1b\n"
 117                 ".previous"
 118                 : "=&r" (ret), "=m" (sem->count)
 119                 : "m" (sem->count));
 120
 121         return ret < 0;
 122 }
 123
 124 static inline void __up(struct semaphore *sem)
 125 {
 126         if (unlikely(atomic_inc_return(&sem->count) <= 0))
 127                 __up_wakeup(sem);
 128 }
 129
 130 #if !defined(CONFIG_DEBUG_SEMAPHORE)
 131 extern inline void down(struct semaphore *sem)
 132 {
 133         __down(sem);
 134 }
 135 extern inline int down_interruptible(struct semaphore *sem)
 136 {
 137         return __down_interruptible(sem);
 138 }
 139 extern inline int down_trylock(struct semaphore *sem)
 140 {
 141         return __down_trylock(sem);
 142 }
 143 extern inline void up(struct semaphore *sem)
 144 {
 145         __up(sem);
 146 }
 147 #endif
 148
 149 #endif