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- Remove apause(). It makes no sense with our present mutex implementation

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since simply unlocking a mutex does not ensure that one of the waiters
   will run and acquire it.  We're more likely to reacquire the mutex
   before anyone else has a chance.  It has also bit me three times now, as
   it's not safe to drop the interlock before sleeping in many cases.

Sponsored by:	Isilon Systems, Inc.
This commit is contained in:
jeff 2005-03-31 04:25:59 +00:00
parent f20140a893
commit c0b4cb178d
1 changed files with 0 additions and 40 deletions
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40
sys/kern/kern_lock.c
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@ -79,7 +79,6 @@ __FBSDID("$FreeBSD$");
static struct mtx lock_mtx;
static int acquire(struct lock **lkpp, int extflags, int wanted);
static int apause(struct lock *lkp, int flags);
static int acquiredrain(struct lock *lkp, int extflags) ;
static void
@ -113,32 +112,6 @@ shareunlock(struct thread *td, struct lock *lkp, int decr) {
}
}
/*
* This is the waitloop optimization.
*/
static int
apause(struct lock *lkp, int flags)
{
#ifdef SMP
int i, lock_wait;
#endif
if ((lkp->lk_flags & flags) == 0)
return 0;
#ifdef SMP
for (lock_wait = LOCK_WAIT_TIME; lock_wait > 0; lock_wait--) {
mtx_unlock(lkp->lk_interlock);
for (i = LOCK_SAMPLE_WAIT; i > 0; i--)
if ((lkp->lk_flags & flags) == 0)
break;
mtx_lock(lkp->lk_interlock);
if ((lkp->lk_flags & flags) == 0)
return 0;
}
#endif
return 1;
}
static int
acquire(struct lock **lkpp, int extflags, int wanted)
{
@ -152,12 +125,6 @@ acquire(struct lock **lkpp, int extflags, int wanted)
return EBUSY;
}
if ((extflags & LK_INTERLOCK) == 0) {
error = apause(lkp, wanted);
if (error == 0)
return 0;
}
s = splhigh();
while ((lkp->lk_flags & wanted) != 0) {
lkp->lk_flags |= LK_WAIT_NONZERO;
@ -496,13 +463,6 @@ acquiredrain(struct lock *lkp, int extflags) {
if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
return EBUSY;
}
if ((extflags & LK_INTERLOCK) == 0) {
error = apause(lkp, LK_ALL);
if (error == 0)
return 0;
}
while (lkp->lk_flags & LK_ALL) {
lkp->lk_flags |= LK_WAITDRAIN;
error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio,