LXR linux/include/asm-cris/semaphore.h

   1/* $Id: semaphore.h,v 1.3 2001/05/08 13:54:09 bjornw Exp $ */
   2
   3/* On the i386 these are coded in asm, perhaps we should as well. Later.. */
   4
   5#ifndef _CRIS_SEMAPHORE_H
   6#define _CRIS_SEMAPHORE_H
   7
   8#define RW_LOCK_BIAS             0x01000000
   9
  10#include <linux/wait.h>
  11#include <linux/spinlock.h>
  12#include <linux/rwsem.h>
  13
  14#include <asm/system.h>
  15#include <asm/atomic.h>
  16
  17/*
  18 * CRIS semaphores, implemented in C-only so far. 
  19 */
  20
  21int printk(const char *fmt, ...);
  22
  23struct semaphore {
  24        atomic_t count;
  25        atomic_t waking;
  26        wait_queue_head_t wait;
  27};
  28
  29#define __SEMAPHORE_INITIALIZER(name, n)                                \
  30{                                                                       \
  31        .count          = ATOMIC_INIT(n),                               \
  32        .waking         = ATOMIC_INIT(0),                               \
  33        .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  34}
  35
  36#define __MUTEX_INITIALIZER(name) \
  37        __SEMAPHORE_INITIALIZER(name,1)
  38
  39#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
  40        struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  41
  42#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
  43#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
  44
  45extern inline void sema_init(struct semaphore *sem, int val)
  46{
  47        *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
  48}
  49
  50extern inline void init_MUTEX (struct semaphore *sem)
  51{
  52        sema_init(sem, 1);
  53}
  54
  55extern inline void init_MUTEX_LOCKED (struct semaphore *sem)
  56{
  57        sema_init(sem, 0);
  58}
  59
  60extern void __down(struct semaphore * sem);
  61extern int __down_interruptible(struct semaphore * sem);
  62extern int __down_trylock(struct semaphore * sem);
  63extern void __up(struct semaphore * sem);
  64
  65/* notice - we probably can do cli/sti here instead of saving */
  66
  67extern inline void down(struct semaphore * sem)
  68{
  69        unsigned long flags;
  70        int failed;
  71
  72        might_sleep();
  73
  74        /* atomically decrement the semaphores count, and if its negative, we wait */
  75        local_save_flags(flags);
  76        local_irq_disable();
  77        failed = --(sem->count.counter) < 0;
  78        local_irq_restore(flags);
  79        if(failed) {
  80                __down(sem);
  81        }
  82}
  83
  84/*
  85 * This version waits in interruptible state so that the waiting
  86 * process can be killed.  The down_interruptible routine
  87 * returns negative for signalled and zero for semaphore acquired.
  88 */
  89
  90extern inline int down_interruptible(struct semaphore * sem)
  91{
  92        unsigned long flags;
  93        int failed;
  94
  95        might_sleep();
  96
  97        /* atomically decrement the semaphores count, and if its negative, we wait */
  98        local_save_flags(flags);
  99        local_irq_disable();
 100        failed = --(sem->count.counter) < 0;
 101        local_irq_restore(flags);
 102        if(failed)
 103                failed = __down_interruptible(sem);
 104        return(failed);
 105}
 106
 107extern inline int down_trylock(struct semaphore * sem)
 108{
 109        unsigned long flags;
 110        int failed;
 111
 112        local_save_flags(flags);
 113        local_irq_disable();
 114        failed = --(sem->count.counter) < 0;
 115        local_irq_restore(flags);
 116        if(failed)
 117                failed = __down_trylock(sem);
 118        return(failed);
 119}
 120
 121/*
 122 * Note! This is subtle. We jump to wake people up only if
 123 * the semaphore was negative (== somebody was waiting on it).
 124 * The default case (no contention) will result in NO
 125 * jumps for both down() and up().
 126 */
 127extern inline void up(struct semaphore * sem)
 128{  
 129        unsigned long flags;
 130        int wakeup;
 131
 132        /* atomically increment the semaphores count, and if it was negative, we wake people */
 133        local_save_flags(flags);
 134        local_irq_disable();
 135        wakeup = ++(sem->count.counter) <= 0;
 136        local_irq_restore(flags);
 137        if(wakeup) {
 138                __up(sem);
 139        }
 140}
 141
 142#endif
 143