46 lines
1.7 KiB
Diff
46 lines
1.7 KiB
Diff
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Thu, 6 Dec 2018 10:15:13 +0100
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Subject: [PATCH] hrtimer: move state change before hrtimer_cancel in
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do_nanosleep()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.10-rt8.tar.xz
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There is a small window between setting t->task to NULL and waking the
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task up (which would set TASK_RUNNING). So the timer would fire, run and
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set ->task to NULL while the other side/do_nanosleep() wouldn't enter
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freezable_schedule(). After all we are peemptible here (in
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do_nanosleep() and on the timer wake up path) and on KVM/virt the
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virt-CPU might get preempted.
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So do_nanosleep() wouldn't enter freezable_schedule() but cancel the
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timer which is still running and wait for it via
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hrtimer_wait_for_timer(). Then wait_event()/might_sleep() would complain
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that it is invoked with state != TASK_RUNNING.
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This isn't a problem since it would be reset to TASK_RUNNING later
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anyway and we don't rely on the previous state.
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Move the state update to TASK_RUNNING before hrtimer_cancel() so there
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are no complains from might_sleep() about wrong state.
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Cc: stable-rt@vger.kernel.org
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Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/time/hrtimer.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/kernel/time/hrtimer.c
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+++ b/kernel/time/hrtimer.c
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@@ -1785,12 +1785,12 @@ static int __sched do_nanosleep(struct h
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if (likely(t->task))
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freezable_schedule();
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+ __set_current_state(TASK_RUNNING);
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hrtimer_cancel(&t->timer);
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mode = HRTIMER_MODE_ABS;
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} while (t->task && !signal_pending(current));
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- __set_current_state(TASK_RUNNING);
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if (!t->task)
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return 0;
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