Commit-ID: aee38ea95419c818dfdde52b115aeffe9cbb259b Gitweb: http://git.kernel.org/tip/aee38ea95419c818dfdde52b115aeffe9cbb259b Author: Juri Lelli <juri.lelli@xxxxxxx> AuthorDate: Fri, 24 Oct 2014 10:16:38 +0100 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Tue, 28 Oct 2014 10:46:01 +0100 sched/deadline: Fix races between rt_mutex_setprio() and dl_task_timer() dl_task_timer() is racy against several paths. Daniel noticed that the replenishment timer may experience a race condition against an enqueue_dl_entity() called from rt_mutex_setprio(). With his own words: rt_mutex_setprio() resets p->dl.dl_throttled. So the pattern is: start_dl_timer() throttled = 1, rt_mutex_setprio() throlled = 0, sched_switch() -> enqueue_task(), dl_task_timer-> enqueue_task() throttled is 0 => BUG_ON(on_dl_rq(dl_se)) fires as the scheduling entity is already enqueued on the -deadline runqueue. As we do for the other races, we just bail out in the replenishment timer code. Reported-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx> Tested-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx> Signed-off-by: Juri Lelli <juri.lelli@xxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: vincent@xxxxxxxxxxx Cc: Dario Faggioli <raistlin@xxxxxxxx> Cc: Michael Trimarchi <michael@xxxxxxxxxxxxxxxxxxxx> Cc: Fabio Checconi <fchecconi@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1414142198-18552-5-git-send-email-juri.lelli@xxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/deadline.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 92279ea..4616789 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -518,12 +518,20 @@ again: } /* - * We need to take care of a possible races here. In fact, the - * task might have changed its scheduling policy to something - * different from SCHED_DEADLINE or changed its reservation - * parameters (through sched_setattr()). + * We need to take care of several possible races here: + * + * - the task might have changed its scheduling policy + * to something different than SCHED_DEADLINE + * - the task might have changed its reservation parameters + * (through sched_setattr()) + * - the task might have been boosted by someone else and + * might be in the boosting/deboosting path + * + * In all this cases we bail out, as the task is already + * in the runqueue or is going to be enqueued back anyway. */ - if (!dl_task(p) || dl_se->dl_new) + if (!dl_task(p) || dl_se->dl_new || + dl_se->dl_boosted || !dl_se->dl_throttled) goto unlock; sched_clock_tick(); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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