Author: hselasky Date: Mon Oct 10 11:27:59 2016 New Revision: 306948 URL: https://svnweb.freebsd.org/changeset/base/306948
Log: MFC r306441 and r306634: While draining a timeout task prevent the taskqueue_enqueue_timeout() function from restarting the timer. Commonly taskqueue_enqueue_timeout() is called from within the task function itself without any checks for teardown. Then it can happen the timer stays active after the return of taskqueue_drain_timeout(), because the timeout and task is drained separately. This patch factors out the teardown flag into the timeout task itself, allowing existing code to stay as-is instead of applying a teardown flag to each and every of the timeout task consumers. Add assert to taskqueue_drain_timeout() which prevents parallel execution on the same timeout task. Update manual page documenting the return value of taskqueue_enqueue_timeout(). Differential Revision: https://reviews.freebsd.org/D8012 Reviewed by: kib, trasz Modified: stable/9/share/man/man9/taskqueue.9 stable/9/sys/kern/subr_taskqueue.c Directory Properties: stable/9/share/ (props changed) stable/9/share/man/ (props changed) stable/9/share/man/man9/ (props changed) stable/9/sys/ (props changed) Modified: stable/9/share/man/man9/taskqueue.9 ============================================================================== --- stable/9/share/man/man9/taskqueue.9 Mon Oct 10 11:25:11 2016 (r306947) +++ stable/9/share/man/man9/taskqueue.9 Mon Oct 10 11:27:59 2016 (r306948) @@ -193,6 +193,8 @@ Otherwise, the task is scheduled for enq after the absolute value of .Va ticks is passed. +This function returns -1 if the task is being drained. +Otherwise, the number of pending calls is returned. .Pp The .Fn taskqueue_cancel Modified: stable/9/sys/kern/subr_taskqueue.c ============================================================================== --- stable/9/sys/kern/subr_taskqueue.c Mon Oct 10 11:25:11 2016 (r306947) +++ stable/9/sys/kern/subr_taskqueue.c Mon Oct 10 11:27:59 2016 (r306948) @@ -70,6 +70,7 @@ struct taskqueue { #define TQ_FLAGS_PENDING (1 << 2) #define DT_CALLOUT_ARMED (1 << 0) +#define DT_DRAIN_IN_PROGRESS (1 << 1) #define TQ_LOCK(tq) \ do { \ @@ -244,7 +245,11 @@ taskqueue_enqueue_timeout(struct taskque KASSERT(!queue->tq_spin, ("Timeout for spin-queue")); timeout_task->q = queue; res = timeout_task->t.ta_pending; - if (ticks == 0) { + if (timeout_task->f & DT_DRAIN_IN_PROGRESS) { + /* Do nothing */ + TQ_UNLOCK(queue); + res = -1; + } else if (ticks == 0) { taskqueue_enqueue_locked(queue, &timeout_task->t); } else { if ((timeout_task->f & DT_CALLOUT_ARMED) != 0) { @@ -434,8 +439,24 @@ taskqueue_drain_timeout(struct taskqueue struct timeout_task *timeout_task) { + /* + * Set flag to prevent timer from re-starting during drain: + */ + TQ_LOCK(queue); + KASSERT((timeout_task->f & DT_DRAIN_IN_PROGRESS) == 0, + ("Drain already in progress")); + timeout_task->f |= DT_DRAIN_IN_PROGRESS; + TQ_UNLOCK(queue); + callout_drain(&timeout_task->c); taskqueue_drain(queue, &timeout_task->t); + + /* + * Clear flag to allow timer to re-start: + */ + TQ_LOCK(queue); + timeout_task->f &= ~DT_DRAIN_IN_PROGRESS; + TQ_UNLOCK(queue); } static void _______________________________________________ svn-src-stable-9@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-stable-9 To unsubscribe, send any mail to "svn-src-stable-9-unsubscr...@freebsd.org"
