diff options
Diffstat (limited to 'sys/kern/kern_timeout.c')
| -rw-r--r-- | sys/kern/kern_timeout.c | 40 |
1 files changed, 27 insertions, 13 deletions
diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c index 2e67ece1f9ed..62ec5754a762 100644 --- a/sys/kern/kern_timeout.c +++ b/sys/kern/kern_timeout.c @@ -491,7 +491,7 @@ _callout_stop_safe(c, safe) struct callout *c; int safe; { - int use_mtx; + int use_mtx, sq_locked; if (!safe && c->c_mtx != NULL) { #ifdef notyet /* Some callers do not hold Giant for Giant-locked callouts. */ @@ -504,6 +504,8 @@ _callout_stop_safe(c, safe) use_mtx = 0; } + sq_locked = 0; +again: mtx_lock_spin(&callout_lock); /* * If the callout isn't pending, it's not on the queue, so @@ -521,6 +523,8 @@ _callout_stop_safe(c, safe) CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p", c, c->c_func, c->c_arg); mtx_unlock_spin(&callout_lock); + if (sq_locked) + sleepq_release(&callout_wait); return (0); } @@ -539,20 +543,24 @@ _callout_stop_safe(c, safe) * a LOR between callout_lock and sleepqueue * chain spinlocks. This piece of code * emulates a msleep_spin() call actually. + * + * If we already have the sleepqueue chain + * locked, then we can safely block. If we + * don't already have it locked, however, + * we have to drop the callout_lock to lock + * it. This opens several races, so we + * restart at the beginning once we have + * both locks. If nothing has changed, then + * we will end up back here with sq_locked + * set. */ - mtx_unlock_spin(&callout_lock); - sleepq_lock(&callout_wait); - - /* - * Check again the state of curr_callout - * because curthread could have lost the - * race previously won. - */ - mtx_lock_spin(&callout_lock); - if (c != curr_callout) { - sleepq_release(&callout_wait); - break; + if (!sq_locked) { + mtx_unlock_spin(&callout_lock); + sleepq_lock(&callout_wait); + sq_locked = 1; + goto again; } + callout_wait = 1; DROP_GIANT(); mtx_unlock_spin(&callout_lock); @@ -560,6 +568,7 @@ _callout_stop_safe(c, safe) &callout_lock.lock_object, "codrain", SLEEPQ_SLEEP, 0); sleepq_wait(&callout_wait); + sq_locked = 0; /* Reacquire locks previously released. */ PICKUP_GIANT(); @@ -577,13 +586,18 @@ _callout_stop_safe(c, safe) CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p", c, c->c_func, c->c_arg); mtx_unlock_spin(&callout_lock); + KASSERT(!sq_locked, ("sleepqueue chain locked")); return (1); } CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p", c, c->c_func, c->c_arg); mtx_unlock_spin(&callout_lock); + KASSERT(!sq_locked, ("sleepqueue chain still locked")); return (0); } + if (sq_locked) + sleepq_release(&callout_wait); + c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING); if (nextsoftcheck == c) { |