include/asm-mips/semaphore.h

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1996  Linus Torvalds
   7  * Copyright (C) 1998, 99, 2000, 01, 04  Ralf Baechle
   8  * Copyright (C) 1999, 2000, 01  Silicon Graphics, Inc.
   9  * Copyright (C) 2000, 01 MIPS Technologies, Inc.
  10  *
  11  * In all honesty, little of the old MIPS code left - the PPC64 variant was
  12  * just looking nice and portable so I ripped it.  Credits to whoever wrote
  13  * it.
  14  */
  15 #ifndef __ASM_SEMAPHORE_H
  16 #define __ASM_SEMAPHORE_H
  17
  18 /*
  19  * Remove spinlock-based RW semaphores; RW semaphore definitions are
  20  * now in rwsem.h and we use the generic lib/rwsem.c implementation.
  21  * Rework semaphores to use atomic_dec_if_positive.
  22  * -- Paul Mackerras (paulus@samba.org)
  23  */
  24
  25 #ifdef __KERNEL__
  26
  27 #include <asm/atomic.h>
  28 #include <asm/system.h>
  29 #include <linux/wait.h>
  30 #include <linux/rwsem.h>
  31
  32 struct semaphore {
  33         /*
  34          * Note that any negative value of count is equivalent to 0,
  35          * but additionally indicates that some process(es) might be
  36          * sleeping on `wait'.
  37          */
  38         atomic_t count;
  39         wait_queue_head_t wait;
  40 };
  41
  42 #define __SEMAPHORE_INITIALIZER(name, n)                                \
  43 {                                                                       \
  44         .count          = ATOMIC_INIT(n),                               \
  45         .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  46 }
  47
  48 #define __DECLARE_SEMAPHORE_GENERIC(name, count) \
  49         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  50
  51 #define DECLARE_MUTEX(name)             __DECLARE_SEMAPHORE_GENERIC(name, 1)
  52 #define DECLARE_MUTEX_LOCKED(name)      __DECLARE_SEMAPHORE_GENERIC(name, 0)
  53
  54 static inline void sema_init (struct semaphore *sem, int val)
  55 {
  56         atomic_set(&sem->count, val);
  57         init_waitqueue_head(&sem->wait);
  58 }
  59
  60 static inline void init_MUTEX (struct semaphore *sem)
  61 {
  62         sema_init(sem, 1);
  63 }
  64
  65 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  66 {
  67         sema_init(sem, 0);
  68 }
  69
  70 extern void __down(struct semaphore * sem);
  71 extern int  __down_interruptible(struct semaphore * sem);
  72 extern void __up(struct semaphore * sem);
  73
  74 static inline void down(struct semaphore * sem)
  75 {
  76         might_sleep();
  77
  78         /*
  79          * Try to get the semaphore, take the slow path if we fail.
  80          */
  81         if (unlikely(atomic_dec_return(&sem->count) < 0))
  82                 __down(sem);
  83 }
  84
  85 static inline int down_interruptible(struct semaphore * sem)
  86 {
  87         int ret = 0;
  88
  89         might_sleep();
  90
  91         if (unlikely(atomic_dec_return(&sem->count) < 0))
  92                 ret = __down_interruptible(sem);
  93         return ret;
  94 }
  95
  96 static inline int down_trylock(struct semaphore * sem)
  97 {
  98         return atomic_dec_if_positive(&sem->count) < 0;
  99 }
 100
 101 static inline void up(struct semaphore * sem)
 102 {
 103         if (unlikely(atomic_inc_return(&sem->count) <= 0))
 104                 __up(sem);
 105 }
 106
 107 #endif /* __KERNEL__ */
 108
 109 #endif /* __ASM_SEMAPHORE_H */