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Revert r282971. It depends on condvar consumers not destroying condvars

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until all threads sleeping on a condvar have resumed execution after being
awakened.  However, there are cases where that guarantee is very hard to
provide.
This commit is contained in:
John Baldwin 2015-05-21 16:43:26 +00:00
parent b6fb3fe0bd
commit c636f94bd2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=283250
2 changed files with 12 additions and 13 deletions
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23
sys/kern/kern_condvar.c
View File

@ -122,7 +122,7 @@ _cv_wait(struct cv *cvp, struct lock_object *lock)
sleepq_lock(cvp);
atomic_add_int(&cvp->cv_waiters, 1);
cvp->cv_waiters++;
if (lock == &Giant.lock_object)
mtx_assert(&Giant, MA_OWNED);
DROP_GIANT();
@ -137,7 +137,6 @@ _cv_wait(struct cv *cvp, struct lock_object *lock)
sleepq_lock(cvp);
}
sleepq_wait(cvp, 0);
atomic_subtract_int(&cvp->cv_waiters, 1);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
@ -185,7 +184,7 @@ _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
sleepq_lock(cvp);
atomic_add_int(&cvp->cv_waiters, 1);
cvp->cv_waiters++;
DROP_GIANT();
sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
@ -195,7 +194,6 @@ _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
if (class->lc_flags & LC_SLEEPABLE)
sleepq_lock(cvp);
sleepq_wait(cvp, 0);
atomic_subtract_int(&cvp->cv_waiters, 1);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
@ -242,7 +240,7 @@ _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
sleepq_lock(cvp);
atomic_add_int(&cvp->cv_waiters, 1);
cvp->cv_waiters++;
if (lock == &Giant.lock_object)
mtx_assert(&Giant, MA_OWNED);
DROP_GIANT();
@ -258,7 +256,6 @@ _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
sleepq_lock(cvp);
}
rval = sleepq_wait_sig(cvp, 0);
atomic_subtract_int(&cvp->cv_waiters, 1);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
@ -310,7 +307,7 @@ _cv_timedwait_sbt(struct cv *cvp, struct lock_object *lock, sbintime_t sbt,
sleepq_lock(cvp);
atomic_add_int(&cvp->cv_waiters, 1);
cvp->cv_waiters++;
if (lock == &Giant.lock_object)
mtx_assert(&Giant, MA_OWNED);
DROP_GIANT();
@ -326,7 +323,6 @@ _cv_timedwait_sbt(struct cv *cvp, struct lock_object *lock, sbintime_t sbt,
sleepq_lock(cvp);
}
rval = sleepq_timedwait(cvp, 0);
atomic_subtract_int(&cvp->cv_waiters, 1);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
@ -380,7 +376,7 @@ _cv_timedwait_sig_sbt(struct cv *cvp, struct lock_object *lock,
sleepq_lock(cvp);
atomic_add_int(&cvp->cv_waiters, 1);
cvp->cv_waiters++;
if (lock == &Giant.lock_object)
mtx_assert(&Giant, MA_OWNED);
DROP_GIANT();
@ -397,7 +393,6 @@ _cv_timedwait_sig_sbt(struct cv *cvp, struct lock_object *lock,
sleepq_lock(cvp);
}
rval = sleepq_timedwait_sig(cvp, 0);
atomic_subtract_int(&cvp->cv_waiters, 1);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
@ -426,8 +421,10 @@ cv_signal(struct cv *cvp)
wakeup_swapper = 0;
sleepq_lock(cvp);
if (cvp->cv_waiters > 0)
if (cvp->cv_waiters > 0) {
cvp->cv_waiters--;
wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 0);
}
sleepq_release(cvp);
if (wakeup_swapper)
kick_proc0();
@ -450,8 +447,10 @@ cv_broadcastpri(struct cv *cvp, int pri)
if (pri == -1)
pri = 0;
sleepq_lock(cvp);
if (cvp->cv_waiters > 0)
if (cvp->cv_waiters > 0) {
cvp->cv_waiters = 0;
wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0);
}
sleepq_release(cvp);
if (wakeup_swapper)
kick_proc0();

2
sys/sys/condvar.h
View File

@ -45,7 +45,7 @@ TAILQ_HEAD(cv_waitq, thread);
*/
struct cv {
const char *cv_description;
volatile int cv_waiters;
int cv_waiters;
};
#ifdef _KERNEL