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
  21 struct semaphore {
  22         atomic_t count;
  23         atomic_t waking;
  24         wait_queue_head_t wait;
  25 };
  26
  27 #define __SEMAPHORE_INITIALIZER(name, n)                                \
  28 {                                                                       \
  29         .count          = ATOMIC_INIT(n),                               \
  30         .waking         = ATOMIC_INIT(0),                               \
  31         .wait           = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
  32 }
  33
  34 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
  35         struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
  36
  37 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
  38 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
  39
  40 static inline void sema_init(struct semaphore *sem, int val)
  41 {
  42         *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
  43 }
  44
  45 static inline void init_MUTEX (struct semaphore *sem)
  46 {
  47         sema_init(sem, 1);
  48 }
  49
  50 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
  51 {
  52         sema_init(sem, 0);
  53 }
  54
  55 extern void __down(struct semaphore * sem);
  56 extern int __down_interruptible(struct semaphore * sem);
  57 extern int __down_trylock(struct semaphore * sem);
  58 extern void __up(struct semaphore * sem);
  59
  60 /* notice - we probably can do cli/sti here instead of saving */
  61
  62 static inline void down(struct semaphore * sem)
  63 {
  64         unsigned long flags;
  65         int failed;
  66
  67         might_sleep();
  68
  69         /* atomically decrement the semaphores count, and if its negative, we wait */
  70         cris_atomic_save(sem, flags);
  71         failed = --(sem->count.counter) < 0;
  72         cris_atomic_restore(sem, flags);
  73         if(failed) {
  74                 __down(sem);
  75         }
  76 }
  77
  78 /*
  79  * This version waits in interruptible state so that the waiting
  80  * process can be killed.  The down_interruptible routine
  81  * returns negative for signalled and zero for semaphore acquired.
  82  */
  83
  84 static inline int down_interruptible(struct semaphore * sem)
  85 {
  86         unsigned long flags;
  87         int failed;
  88
  89         might_sleep();
  90
  91         /* atomically decrement the semaphores count, and if its negative, we wait */
  92         cris_atomic_save(sem, flags);
  93         failed = --(sem->count.counter) < 0;
  94         cris_atomic_restore(sem, flags);
  95         if(failed)
  96                 failed = __down_interruptible(sem);
  97         return(failed);
  98 }
  99
 100 static inline int down_trylock(struct semaphore * sem)
 101 {
 102         unsigned long flags;
 103         int failed;
 104
 105         cris_atomic_save(sem, flags);
 106         failed = --(sem->count.counter) < 0;
 107         cris_atomic_restore(sem, flags);
 108         if(failed)
 109                 failed = __down_trylock(sem);
 110         return(failed);
 111
 112 }
 113
 114 /*
 115  * Note! This is subtle. We jump to wake people up only if
 116  * the semaphore was negative (== somebody was waiting on it).
 117  * The default case (no contention) will result in NO
 118  * jumps for both down() and up().
 119  */
 120 static inline void up(struct semaphore * sem)
 121 {
 122         unsigned long flags;
 123         int wakeup;
 124
 125         /* atomically increment the semaphores count, and if it was negative, we wake people */
 126         cris_atomic_save(sem, flags);
 127         wakeup = ++(sem->count.counter) <= 0;
 128         cris_atomic_restore(sem, flags);
 129         if(wakeup) {
 130                 __up(sem);
 131         }
 132 }
 133
 134 #endif