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
  40 static inline void sema_init (struct semaphore *sem, int val)
  41 {
  42         atomic_set(&sem->count, val);
  43         sem->sleepers = 0;
  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 void __down(struct semaphore * sem);
  58 int  __down_interruptible(struct semaphore * sem);
  59 void __up(struct semaphore * sem);
  60
  61 /*
  62  * This is ugly, but we want the default case to fall through.
  63  * "__down_failed" is a special asm handler that calls the C
  64  * routine that actually waits. See arch/i386/kernel/semaphore.c
  65  */
  66 static inline void down(struct semaphore * sem)
  67 {
  68         might_sleep();
  69         if (unlikely(atomic_dec_return (&sem->count) < 0))
  70                 __down (sem);
  71 }
  72
  73 /*
  74  * Interruptible try to acquire a semaphore.  If we obtained
  75  * it, return zero.  If we were interrupted, returns -EINTR
  76  */
  77 static inline int down_interruptible(struct semaphore * sem)
  78 {
  79         int ret = 0;
  80
  81         might_sleep();
  82         if (unlikely(atomic_dec_return (&sem->count) < 0))
  83                 ret = __down_interruptible (sem);
  84         return ret;
  85 }
  86
  87 /*
  88  * Non-blockingly attempt to down() a semaphore.
  89  * Returns zero if we acquired it
  90  */
  91 static inline int down_trylock(struct semaphore * sem)
  92 {
  93         return atomic_dec_if_positive(&sem->count) < 0;
  94 }
  95
  96 /*
  97  * Note! This is subtle. We jump to wake people up only if
  98  * the semaphore was negative (== somebody was waiting on it).
  99  * The default case (no contention) will result in NO
 100  * jumps for both down() and up().
 101  */
 102 static inline void up(struct semaphore * sem)
 103 {
 104         if (unlikely(atomic_inc_return (&sem->count) <= 0))
 105                 __up (sem);
 106 }
 107
 108 #endif /*__ASM_AVR32_SEMAPHORE_H */