include/asm-avr32/semaphore.h

   1 /*
   2  * SMP- and interrupt-safe semaphores.
   3  *
   4  * Copyright (C) 2006 Atmel Corporation
   5  *
   6  * Based on include/asm-i386/semaphore.h
   7  *   Copyright (C) 1996 Linus Torvalds
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  */
  13 #ifndef __ASM_AVR32_SEMAPHORE_H
  14 #define __ASM_AVR32_SEMAPHORE_H
  15
  16 #include <linux/linkage.h>
  17
  18 #include <asm/system.h>
  19 #include <asm/atomic.h>
  20 #include <linux/wait.h>
  21 #include <linux/rwsem.h>
  22
  23 struct semaphore {
  24         atomic_t count;
  25         int sleepers;
  26         wait_queue_head_t wait;
  27 };
  28
  29 #define __SEMAPHORE_INITIALIZER(name, n)                                \
  30 {                                                                       \
  31         .count          = ATOMIC_INIT(n),                               \
  32         .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  33 }
  34
  35 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
  36         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  37
  38 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
  39 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
  40
  41 static inline void sema_init (struct semaphore *sem, int val)
  42 {
  43         atomic_set(&sem->count, val);
  44         sem->sleepers = 0;
  45         init_waitqueue_head(&sem->wait);
  46 }
  47
  48 static inline void init_MUTEX (struct semaphore *sem)
  49 {
  50         sema_init(sem, 1);
  51 }
  52
  53 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  54 {
  55         sema_init(sem, 0);
  56 }
  57
  58 void __down(struct semaphore * sem);
  59 int  __down_interruptible(struct semaphore * sem);
  60 void __up(struct semaphore * sem);
  61
  62 /*
  63  * This is ugly, but we want the default case to fall through.
  64  * "__down_failed" is a special asm handler that calls the C
  65  * routine that actually waits. See arch/i386/kernel/semaphore.c
  66  */
  67 static inline void down(struct semaphore * sem)
  68 {
  69         might_sleep();
  70         if (unlikely(atomic_dec_return (&sem->count) < 0))
  71                 __down (sem);
  72 }
  73
  74 /*
  75  * Interruptible try to acquire a semaphore.  If we obtained
  76  * it, return zero.  If we were interrupted, returns -EINTR
  77  */
  78 static inline int down_interruptible(struct semaphore * sem)
  79 {
  80         int ret = 0;
  81
  82         might_sleep();
  83         if (unlikely(atomic_dec_return (&sem->count) < 0))
  84                 ret = __down_interruptible (sem);
  85         return ret;
  86 }
  87
  88 /*
  89  * Non-blockingly attempt to down() a semaphore.
  90  * Returns zero if we acquired it
  91  */
  92 static inline int down_trylock(struct semaphore * sem)
  93 {
  94         return atomic_dec_if_positive(&sem->count) < 0;
  95 }
  96
  97 /*
  98  * Note! This is subtle. We jump to wake people up only if
  99  * the semaphore was negative (== somebody was waiting on it).
 100  * The default case (no contention) will result in NO
 101  * jumps for both down() and up().
 102  */
 103 static inline void up(struct semaphore * sem)
 104 {
 105         if (unlikely(atomic_inc_return (&sem->count) <= 0))
 106                 __up (sem);
 107 }
 108
 109 #endif /*__ASM_AVR32_SEMAPHORE_H */