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
  53 static inline void sema_init(struct semaphore *sem, int val)
  54 {
  55         atomic_set(&sem->count, val);
  56         init_waitqueue_head(&sem->wait);
  57 }
  58
  59 static inline void init_MUTEX(struct semaphore *sem)
  60 {
  61         sema_init(sem, 1);
  62 }
  63
  64 static inline void init_MUTEX_LOCKED(struct semaphore *sem)
  65 {
  66         sema_init(sem, 0);
  67 }
  68
  69 extern void __down(struct semaphore * sem);
  70 extern int  __down_interruptible(struct semaphore * sem);
  71 extern void __up(struct semaphore * sem);
  72
  73 static inline void down(struct semaphore * sem)
  74 {
  75         might_sleep();
  76
  77         /*
  78          * Try to get the semaphore, take the slow path if we fail.
  79          */
  80         if (unlikely(atomic_dec_return(&sem->count) < 0))
  81                 __down(sem);
  82 }
  83
  84 static inline int down_interruptible(struct semaphore * sem)
  85 {
  86         int ret = 0;
  87
  88         might_sleep();
  89
  90         if (unlikely(atomic_dec_return(&sem->count) < 0))
  91                 ret = __down_interruptible(sem);
  92         return ret;
  93 }
  94
  95 static inline int down_trylock(struct semaphore * sem)
  96 {
  97         return atomic_dec_if_positive(&sem->count) < 0;
  98 }
  99
 100 static inline void up(struct semaphore * sem)
 101 {
 102         if (unlikely(atomic_inc_return(&sem->count) <= 0))
 103                 __up(sem);
 104 }
 105
 106 #endif /* __KERNEL__ */
 107
 108 #endif /* __ASM_SEMAPHORE_H */