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Fix cv_timedwait timeout

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Perform the already past expiration time check before updating
cvp->cv_mutex with the provided mutex.  This check only depends
on local state.  Doing it first ensures that cvp->cv_mutex will not
be updated in the timeout case or if it's ever called with an
expire_time <= now.

Reviewed-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #616
This commit is contained in:
Brian Behlendorf 2017-05-25 10:01:44 -07:00 committed by GitHub
parent 8f87971e1f
commit 2ded1c7eff
1 changed files with 12 additions and 18 deletions
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30
module/spl/spl-condvar.c
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@ -166,22 +166,19 @@ __cv_timedwait_common(kcondvar_t *cvp, kmutex_t *mp, clock_t expire_time,
ASSERT(mp); ASSERT(mp);
ASSERT(cvp->cv_magic == CV_MAGIC); ASSERT(cvp->cv_magic == CV_MAGIC);
ASSERT(mutex_owned(mp)); ASSERT(mutex_owned(mp));
atomic_inc(&cvp->cv_refs);
/* XXX - Does not handle jiffie wrap properly */
time_left = expire_time - jiffies;
if (time_left <= 0)
return (-1);
atomic_inc(&cvp->cv_refs);
m = ACCESS_ONCE(cvp->cv_mutex); m = ACCESS_ONCE(cvp->cv_mutex);
if (!m) if (!m)
m = xchg(&cvp->cv_mutex, mp); m = xchg(&cvp->cv_mutex, mp);
/* Ensure the same mutex is used by all callers */ /* Ensure the same mutex is used by all callers */
ASSERT(m == NULL || m == mp); ASSERT(m == NULL || m == mp);
/* XXX - Does not handle jiffie wrap properly */
time_left = expire_time - jiffies;
if (time_left <= 0) {
/* XXX - doesn't reset cv_mutex */
atomic_dec(&cvp->cv_refs);
return (-1);
}
prepare_to_wait_exclusive(&cvp->cv_event, &wait, state); prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
atomic_inc(&cvp->cv_waiters); atomic_inc(&cvp->cv_waiters);
@ -238,28 +235,25 @@ __cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp, hrtime_t expire_time,
{ {
DEFINE_WAIT(wait); DEFINE_WAIT(wait);
kmutex_t *m; kmutex_t *m;
hrtime_t time_left, now; hrtime_t time_left;
ktime_t ktime_left; ktime_t ktime_left;
ASSERT(cvp); ASSERT(cvp);
ASSERT(mp); ASSERT(mp);
ASSERT(cvp->cv_magic == CV_MAGIC); ASSERT(cvp->cv_magic == CV_MAGIC);
ASSERT(mutex_owned(mp)); ASSERT(mutex_owned(mp));
atomic_inc(&cvp->cv_refs);
time_left = expire_time - gethrtime();
if (time_left <= 0)
return (-1);
atomic_inc(&cvp->cv_refs);
m = ACCESS_ONCE(cvp->cv_mutex); m = ACCESS_ONCE(cvp->cv_mutex);
if (!m) if (!m)
m = xchg(&cvp->cv_mutex, mp); m = xchg(&cvp->cv_mutex, mp);
/* Ensure the same mutex is used by all callers */ /* Ensure the same mutex is used by all callers */
ASSERT(m == NULL || m == mp); ASSERT(m == NULL || m == mp);
now = gethrtime();
time_left = expire_time - now;
if (time_left <= 0) {
atomic_dec(&cvp->cv_refs);
return (-1);
}
prepare_to_wait_exclusive(&cvp->cv_event, &wait, state); prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
atomic_inc(&cvp->cv_waiters); atomic_inc(&cvp->cv_waiters);