diff options
author | Kirill Tkhai <tkhai@yandex.ru> | 2015-02-16 15:38:34 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2015-02-18 14:27:31 +0100 |
commit | a79ec89fd8459f0de850898f432a2a57d60e64de (patch) | |
tree | 23b42d39bfc96342d22cd55dade4fef1c52f89ef /kernel/sched/deadline.c | |
parent | 3960c8c0c7891dfc0f7be687cbdabb0d6916d614 (diff) | |
download | linux-a79ec89fd8459f0de850898f432a2a57d60e64de.tar.bz2 |
sched/dl: Prevent enqueue of a sleeping task in dl_task_timer()
A deadline task may be throttled and dequeued at the same time.
This happens, when it becomes throttled in schedule(), which
is called to go to sleep:
current->state = TASK_INTERRUPTIBLE;
schedule()
deactivate_task()
dequeue_task_dl()
update_curr_dl()
start_dl_timer()
__dequeue_task_dl()
prev->on_rq = 0;
Later the timer fires, but the task is still dequeued:
dl_task_timer()
enqueue_task_dl() /* queues on dl_rq; on_rq remains 0 */
Someone wakes it up:
try_to_wake_up()
enqueue_dl_entity()
BUG_ON(on_dl_rq())
Patch fixes this problem, it prevents queueing !on_rq tasks
on dl_rq.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Wrote comment. ]
Cc: Juri Lelli <juri.lelli@arm.com>
Fixes: 1019a359d3dc ("sched/deadline: Fix stale yield state")
Link: http://lkml.kernel.org/r/1374601424090314@web4j.yandex.ru
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/deadline.c')
-rw-r--r-- | kernel/sched/deadline.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index e88847d9fc6a..9908c950d776 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -535,6 +535,26 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) sched_clock_tick(); update_rq_clock(rq); + + /* + * If the throttle happened during sched-out; like: + * + * schedule() + * deactivate_task() + * dequeue_task_dl() + * update_curr_dl() + * start_dl_timer() + * __dequeue_task_dl() + * prev->on_rq = 0; + * + * We can be both throttled and !queued. Replenish the counter + * but do not enqueue -- wait for our wakeup to do that. + */ + if (!task_on_rq_queued(p)) { + replenish_dl_entity(dl_se, dl_se); + goto unlock; + } + enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); if (dl_task(rq->curr)) check_preempt_curr_dl(rq, p, 0); |