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 __MUTEX_INITIALIZER(name) \
  33         __SEMAPHORE_INITIALIZER(name,1)
  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         *sem = (struct semaphore) __SEMAPHORE_INITIALIZER((*sem),val);
  44 }
  45
  46 static inline void init_MUTEX (struct semaphore *sem)
  47 {
  48         sema_init(sem, 1);
  49 }
  50
  51 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  52 {
  53         sema_init(sem, 0);
  54 }
  55
  56 asmlinkage void __down(struct semaphore * sem);
  57 asmlinkage int  __down_interruptible(struct semaphore * sem);
  58 asmlinkage int  __down_trylock(struct semaphore * sem);
  59 asmlinkage void __up(struct semaphore * sem);
  60
  61 static inline void down(struct semaphore * sem)
  62 {
  63         might_sleep();
  64         if (atomic_dec_return(&sem->count) < 0)
  65                 __down(sem);
  66 }
  67
  68 static inline int down_interruptible(struct semaphore * sem)
  69 {
  70         int ret = 0;
  71
  72         might_sleep();
  73         if (atomic_dec_return(&sem->count) < 0)
  74                 ret = __down_interruptible(sem);
  75         return ret;
  76 }
  77
  78 static inline int down_trylock(struct semaphore * sem)
  79 {
  80         int old_val, new_val;
  81
  82         /*
  83          * This inline assembly atomically implements the equivalent
  84          * to the following C code:
  85          *   old_val = sem->count.counter;
  86          *   if ((new_val = old_val) > 0)
  87          *       sem->count.counter = --new_val;
  88          * In the ppc code this is called atomic_dec_if_positive.
  89          */
  90         __asm__ __volatile__ (
  91                 "   l    %0,0(%3)\n"
  92                 "0: ltr  %1,%0\n"
  93                 "   jle  1f\n"
  94                 "   ahi  %1,-1\n"
  95                 "   cs   %0,%1,0(%3)\n"
  96                 "   jl   0b\n"
  97                 "1:"
  98                 : "=&d" (old_val), "=&d" (new_val), "=m" (sem->count.counter)
  99                 : "a" (&sem->count.counter), "m" (sem->count.counter)
 100                 : "cc", "memory" );
 101         return old_val <= 0;
 102 }
 103
 104 static inline void up(struct semaphore * sem)
 105 {
 106         if (atomic_inc_return(&sem->count) <= 0)
 107                 __up(sem);
 108 }
 109
 110 #endif