include/asm-s390/semaphore.h

   1 /*
   2  *  include/asm-s390/semaphore.h
   3  *
   4  *  S390 version
   5  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   6  *
   7  *  Derived from "include/asm-i386/semaphore.h"
   8  *    (C) Copyright 1996 Linus Torvalds
   9  */
  10
  11 #ifndef _S390_SEMAPHORE_H
  12 #define _S390_SEMAPHORE_H
  13
  14 #include <asm/system.h>
  15 #include <asm/atomic.h>
  16 #include <linux/wait.h>
  17 #include <linux/rwsem.h>
  18
  19 struct semaphore {
  20         /*
  21          * Note that any negative value of count is equivalent to 0,
  22          * but additionally indicates that some process(es) might be
  23          * sleeping on `wait'.
  24          */
  25         atomic_t count;
  26         wait_queue_head_t wait;
  27 };
  28
  29 #define __SEMAPHORE_INITIALIZER(name,count) \
  30         { ATOMIC_INIT(count), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) }
  31
  32 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
  33         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  34
  35 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
  36 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
  37
  38 static inline void sema_init (struct semaphore *sem, int val)
  39 {
  40         atomic_set(&sem->count, val);
  41         init_waitqueue_head(&sem->wait);
  42 }
  43
  44 static inline void init_MUTEX (struct semaphore *sem)
  45 {
  46         sema_init(sem, 1);
  47 }
  48
  49 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  50 {
  51         sema_init(sem, 0);
  52 }
  53
  54 asmlinkage void __down(struct semaphore * sem);
  55 asmlinkage int  __down_interruptible(struct semaphore * sem);
  56 asmlinkage int  __down_trylock(struct semaphore * sem);
  57 asmlinkage void __up(struct semaphore * sem);
  58
  59 static inline void down(struct semaphore * sem)
  60 {
  61         might_sleep();
  62         if (atomic_dec_return(&sem->count) < 0)
  63                 __down(sem);
  64 }
  65
  66 static inline int down_interruptible(struct semaphore * sem)
  67 {
  68         int ret = 0;
  69
  70         might_sleep();
  71         if (atomic_dec_return(&sem->count) < 0)
  72                 ret = __down_interruptible(sem);
  73         return ret;
  74 }
  75
  76 static inline int down_trylock(struct semaphore * sem)
  77 {
  78         int old_val, new_val;
  79
  80         /*
  81          * This inline assembly atomically implements the equivalent
  82          * to the following C code:
  83          *   old_val = sem->count.counter;
  84          *   if ((new_val = old_val) > 0)
  85          *       sem->count.counter = --new_val;
  86          * In the ppc code this is called atomic_dec_if_positive.
  87          */
  88         asm volatile(
  89                 "       l       %0,0(%3)\n"
  90                 "0:     ltr     %1,%0\n"
  91                 "       jle     1f\n"
  92                 "       ahi     %1,-1\n"
  93                 "       cs      %0,%1,0(%3)\n"
  94                 "       jl      0b\n"
  95                 "1:"
  96                 : "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter)
  97                 : "a" (&sem->count.counter), "m" (sem->count.counter)
  98                 : "cc", "memory");
  99         return old_val <= 0;
 100 }
 101
 102 static inline void up(struct semaphore * sem)
 103 {
 104         if (atomic_inc_return(&sem->count) <= 0)
 105                 __up(sem);
 106 }
 107
 108 #endif