/* $Id: semaphore.c,v 1.9 2001/11/18 00:12:56 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>
#include <linux/errno.h>
#include <linux/init.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"
" membar #StoreLoad | #StoreStore\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;
}
static void __up(struct semaphore *sem)
{
__sem_update_count(sem, 1);
wake_up(&sem->wait);
}
void up(struct semaphore *sem)
{
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count + 1;
* sem->count = new_val;
* if (old_val < 0)
* __up(sem);
*
* The (old_val < 0) test is equivalent to
* the more straightforward (new_val <= 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! up sem(%0)\n"
" membar #StoreLoad | #LoadLoad\n"
"1: lduw [%0], %%g1\n"
" add %%g1, 1, %%g7\n"
" cas [%0], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" addcc %%g7, 1, %%g0\n"
" membar #StoreLoad | #StoreStore\n"
" ble,pn %%icc, 3f\n"
" nop\n"
"2:\n"
" .subsection 2\n"
"3: mov %0, %%g1\n"
" save %%sp, -160, %%sp\n"
" call %1\n"
" mov %%g1, %%o0\n"
" ba,pt %%xcc, 2b\n"
" restore\n"
" .previous\n"
: : "r" (sem), "i" (__up)
: "g1", "g2", "g3", "g7", "memory", "cc");
}
static void __sched __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);
}
void __sched down(struct semaphore *sem)
{
might_sleep();
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count - 1;
* sem->count = new_val;
* if (old_val < 1)
* __down(sem);
*
* The (old_val < 1) test is equivalent to
* the more straightforward (new_val < 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! down sem(%0)\n"
"1: lduw [%0], %%g1\n"
" sub %%g1, 1, %%g7\n"
" cas [%0], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" cmp %%g7, 1\n"
" membar #StoreLoad | #StoreStore\n"
" bl,pn %%icc, 3f\n"
" nop\n"
"2:\n"
" .subsection 2\n"
"3: mov %0, %%g1\n"
" save %%sp, -160, %%sp\n"
" call %1\n"
" mov %%g1, %%o0\n"
" ba,pt %%xcc, 2b\n"
" restore\n"
" .previous\n"
: : "r" (sem), "i" (__down)
: "g1", "g2", "g3", "g7", "memory", "cc");
}
int down_trylock(struct semaphore *sem)
{
int ret;
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count - 1;
* if (old_val < 1) {
* ret = 1;
* } else {
* sem->count = new_val;
* ret = 0;
* }
*
* The (old_val < 1) test is equivalent to
* the more straightforward (new_val < 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! down_trylock sem(%1) ret(%0)\n"
"1: lduw [%1], %%g1\n"
" sub %%g1, 1, %%g7\n"
" cmp %%g1, 1\n"
" bl,pn %%icc, 2f\n"
" mov 1, %0\n"
" cas [%1], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" mov 0, %0\n"
" membar #StoreLoad | #StoreStore\n"
"2:\n"
: "=&r" (ret)
: "r" (sem)
: "g1", "g7", "memory", "cc");
return ret;
}
static int __sched __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;
}
int __sched down_interruptible(struct semaphore *sem)
{
int ret = 0;
might_sleep();
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count - 1;
* sem->count = new_val;
* if (old_val < 1)
* ret = __down_interruptible(sem);
*
* The (old_val < 1) test is equivalent to
* the more straightforward (new_val < 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! down_interruptible sem(%2) ret(%0)\n"
"1: lduw [%2], %%g1\n"
" sub %%g1, 1, %%g7\n"
" cas [%2], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" cmp %%g7, 1\n"
" membar #StoreLoad | #StoreStore\n"
" bl,pn %%icc, 3f\n"
" nop\n"
"2:\n"
" .subsection 2\n"
"3: mov %2, %%g1\n"
" save %%sp, -160, %%sp\n"
" call %3\n"
" mov %%g1, %%o0\n"
" ba,pt %%xcc, 2b\n"
" restore\n"
" .previous\n"
: "=r" (ret)
: "0" (ret), "r" (sem), "i" (__down_interruptible)
: "g1", "g2", "g3", "g7", "memory", "cc");
return ret;
}
