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 #define DECLARE_MUTEX_LOCKED(name)      __DECLARE_SEMAPHORE_GENERIC(name,0)
  34
  35 static inline void sema_init(struct semaphore *sem, int val)
  36 {
  37         /*
  38          * Logically,
  39          *   *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
  40          * except that gcc produces better initializing by parts yet.
  41          */
  42
  43         atomic_set(&sem->count, val);
  44         init_waitqueue_head(&sem->wait);
  45 }
  46
  47 static inline void init_MUTEX (struct semaphore *sem)
  48 {
  49         sema_init(sem, 1);
  50 }
  51
  52 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  53 {
  54         sema_init(sem, 0);
  55 }
  56
  57 extern void down(struct semaphore *);
  58 extern void __down_failed(struct semaphore *);
  59 extern int  down_interruptible(struct semaphore *);
  60 extern int  __down_failed_interruptible(struct semaphore *);
  61 extern int  down_trylock(struct semaphore *);
  62 extern void up(struct semaphore *);
  63 extern void __up_wakeup(struct semaphore *);
  64
  65 /*
  66  * Hidden out of line code is fun, but extremely messy.  Rely on newer
  67  * compilers to do a respectable job with this.  The contention cases
  68  * are handled out of line in arch/alpha/kernel/semaphore.c.
  69  */
  70
  71 static inline void __down(struct semaphore *sem)
  72 {
  73         long count;
  74         might_sleep();
  75         count = atomic_dec_return(&sem->count);
  76         if (unlikely(count < 0))
  77                 __down_failed(sem);
  78 }
  79
  80 static inline int __down_interruptible(struct semaphore *sem)
  81 {
  82         long count;
  83         might_sleep();
  84         count = atomic_dec_return(&sem->count);
  85         if (unlikely(count < 0))
  86                 return __down_failed_interruptible(sem);
  87         return 0;
  88 }
  89
  90 /*
  91  * down_trylock returns 0 on success, 1 if we failed to get the lock.
  92  */
  93
  94 static inline int __down_trylock(struct semaphore *sem)
  95 {
  96         long ret;
  97
  98         /* "Equivalent" C:
  99
 100            do {
 101                 ret = ldl_l;
 102                 --ret;
 103                 if (ret < 0)
 104                         break;
 105                 ret = stl_c = ret;
 106            } while (ret == 0);
 107         */
 108         __asm__ __volatile__(
 109                 "1:     ldl_l   %0,%1\n"
 110                 "       subl    %0,1,%0\n"
 111                 "       blt     %0,2f\n"
 112                 "       stl_c   %0,%1\n"
 113                 "       beq     %0,3f\n"
 114                 "       mb\n"
 115                 "2:\n"
 116                 ".subsection 2\n"
 117                 "3:     br      1b\n"
 118                 ".previous"
 119                 : "=&r" (ret), "=m" (sem->count)
 120                 : "m" (sem->count));
 121
 122         return ret < 0;
 123 }
 124
 125 static inline void __up(struct semaphore *sem)
 126 {
 127         if (unlikely(atomic_inc_return(&sem->count) <= 0))
 128                 __up_wakeup(sem);
 129 }
 130
 131 #if !defined(CONFIG_DEBUG_SEMAPHORE)
 132 extern inline void down(struct semaphore *sem)
 133 {
 134         __down(sem);
 135 }
 136 extern inline int down_interruptible(struct semaphore *sem)
 137 {
 138         return __down_interruptible(sem);
 139 }
 140 extern inline int down_trylock(struct semaphore *sem)
 141 {
 142         return __down_trylock(sem);
 143 }
 144 extern inline void up(struct semaphore *sem)
 145 {
 146         __up(sem);
 147 }
 148 #endif
 149
 150 #endif