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Fix a potential LOR with sx_sleep() and cv_wait() with sx locks by

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1) adding the thread to the sleepq via sleepq_add() before dropping the
lock, and 2) dropping the sleepq lock around calls to lc_unlock() for
sleepable locks (i.e. locks that use sleepq's in their implementation).
This commit is contained in:
John Baldwin 2007-05-08 21:49:59 +00:00
parent fb610ca1f9
commit 9fa7ce0f23
2 changed files with 32 additions and 6 deletions
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30
sys/kern/kern_condvar.c
View File

@ -124,9 +124,13 @@ _cv_wait(struct cv *cvp, struct lock_object *lock)
cvp->cv_waiters++;
DROP_GIANT();
lock_state = class->lc_unlock(lock);
sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_release(cvp);
lock_state = class->lc_unlock(lock);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_lock(cvp);
sleepq_wait(cvp);
#ifdef KTRACE
@ -173,9 +177,13 @@ _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
cvp->cv_waiters++;
DROP_GIANT();
class->lc_unlock(lock);
sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_release(cvp);
class->lc_unlock(lock);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_lock(cvp);
sleepq_wait(cvp);
#ifdef KTRACE
@ -226,10 +234,14 @@ _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
cvp->cv_waiters++;
DROP_GIANT();
lock_state = class->lc_unlock(lock);
sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
SLEEPQ_INTERRUPTIBLE, 0);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_release(cvp);
lock_state = class->lc_unlock(lock);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_lock(cvp);
rval = sleepq_wait_sig(cvp);
#ifdef KTRACE
@ -282,10 +294,14 @@ _cv_timedwait(struct cv *cvp, struct lock_object *lock, int timo)
cvp->cv_waiters++;
DROP_GIANT();
lock_state = class->lc_unlock(lock);
sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
sleepq_set_timeout(cvp, timo);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_release(cvp);
lock_state = class->lc_unlock(lock);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_lock(cvp);
rval = sleepq_timedwait(cvp);
#ifdef KTRACE
@ -341,11 +357,15 @@ _cv_timedwait_sig(struct cv *cvp, struct lock_object *lock, int timo)
cvp->cv_waiters++;
DROP_GIANT();
lock_state = class->lc_unlock(lock);
sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
SLEEPQ_INTERRUPTIBLE, 0);
sleepq_set_timeout(cvp, timo);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_release(cvp);
lock_state = class->lc_unlock(lock);
if (class->lc_flags & LC_SLEEPABLE)
sleepq_lock(cvp);
rval = sleepq_timedwait_sig(cvp);
#ifdef KTRACE

8
sys/kern/kern_synch.c
View File

@ -182,7 +182,7 @@ _sleep(ident, lock, priority, wmesg, timo)
td->td_tid, p->p_pid, p->p_comm, wmesg, ident);
DROP_GIANT();
if (lock != NULL) {
if (lock != NULL && !(class->lc_flags & LC_SLEEPABLE)) {
WITNESS_SAVE(lock, lock_witness);
lock_state = class->lc_unlock(lock);
} else
@ -201,6 +201,12 @@ _sleep(ident, lock, priority, wmesg, timo)
sleepq_add(ident, ident == &lbolt ? NULL : lock, wmesg, flags, 0);
if (timo)
sleepq_set_timeout(ident, timo);
if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
sleepq_release(ident);
WITNESS_SAVE(lock, lock_witness);
lock_state = class->lc_unlock(lock);
sleepq_lock(ident);
}
/*
* Adjust this thread's priority, if necessary.