Date: Thu, 29 Sep 2016 10:38:21 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r306441 - in head: share/man/man9 sys/kern Message-ID: <201609291038.u8TAcLfO045154@repo.freebsd.org>
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Author: hselasky Date: Thu Sep 29 10:38:20 2016 New Revision: 306441 URL: https://svnweb.freebsd.org/changeset/base/306441 Log: 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 MFC after: 1 week Modified: head/share/man/man9/taskqueue.9 head/sys/kern/subr_taskqueue.c Modified: head/share/man/man9/taskqueue.9 ============================================================================== --- head/share/man/man9/taskqueue.9 Thu Sep 29 09:16:02 2016 (r306440) +++ head/share/man/man9/taskqueue.9 Thu Sep 29 10:38:20 2016 (r306441) @@ -223,6 +223,8 @@ Otherwise, the task is scheduled for enq after the absolute value of .Va ticks is passed. +This function will return -1 if the queue is being drained. +Otherwise the number of pending calls will be returned. .Pp The .Fn taskqueue_cancel Modified: head/sys/kern/subr_taskqueue.c ============================================================================== --- head/sys/kern/subr_taskqueue.c Thu Sep 29 09:16:02 2016 (r306440) +++ head/sys/kern/subr_taskqueue.c Thu Sep 29 10:38:20 2016 (r306441) @@ -81,6 +81,7 @@ struct taskqueue { #define TQ_FLAGS_UNLOCKED_ENQUEUE (1 << 2) #define DT_CALLOUT_ARMED (1 << 0) +#define DT_DRAIN_IN_PROGRESS (1 << 1) #define TQ_LOCK(tq) \ do { \ @@ -299,7 +300,11 @@ 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); /* The lock is released inside. */ } else { @@ -559,8 +564,24 @@ 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
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