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/* $Id: semaphore.c,v 1.8 2001/05/18 08:01:35 davem Exp $
* semaphore.c: Sparc64 semaphore implementation.
*
* This is basically the PPC semaphore scheme ported to use
* the sparc64 atomic instructions, so see the PPC code for
* credits.
*/
#include <linux/sched.h>
/*
* Atomically update sem->count.
* This does the equivalent of the following:
*
* old_count = sem->count;
* tmp = MAX(old_count, 0) + incr;
* sem->count = tmp;
* return old_count;
*/
static __inline__ int __sem_update_count(struct semaphore *sem, int incr)
{
int old_count, tmp;
__asm__ __volatile__("\n"
" ! __sem_update_count old_count(%0) tmp(%1) incr(%4) &sem->count(%3)\n"
"1: ldsw [%3], %0\n"
" mov %0, %1\n"
" cmp %0, 0\n"
" movl %%icc, 0, %1\n"
" add %1, %4, %1\n"
" cas [%3], %0, %1\n"
" cmp %0, %1\n"
" bne,pn %%icc, 1b\n"
" nop\n"
: "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
: "r" (&sem->count), "r" (incr), "m" (sem->count)
: "cc");
return old_count;
}
void __up(struct semaphore *sem)
{
__sem_update_count(sem, 1);
wake_up(&sem->wait);
}
void __down(struct semaphore * sem)
{
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
tsk->state = TASK_UNINTERRUPTIBLE;
add_wait_queue_exclusive(&sem->wait, &wait);
while (__sem_update_count(sem, -1) <= 0) {
schedule();
tsk->state = TASK_UNINTERRUPTIBLE;
}
remove_wait_queue(&sem->wait, &wait);
tsk->state = TASK_RUNNING;
wake_up(&sem->wait);
}
int __down_interruptible(struct semaphore * sem)
{
int retval = 0;
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
tsk->state = TASK_INTERRUPTIBLE;
add_wait_queue_exclusive(&sem->wait, &wait);
while (__sem_update_count(sem, -1) <= 0) {
if (signal_pending(current)) {
__sem_update_count(sem, 0);
retval = -EINTR;
break;
}
schedule();
tsk->state = TASK_INTERRUPTIBLE;
}
tsk->state = TASK_RUNNING;
remove_wait_queue(&sem->wait, &wait);
wake_up(&sem->wait);
return retval;
}
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