There is a small window between setting t->task to NULL and waking the task up (which would set TASK_RUNNING). So the timer would fire, run and set ->task to NULL while the other side/do_nanosleep() wouldn't enter freezable_schedule(). After all we are peemptible here (in do_nanosleep() and on the timer wake up path) and on KVM/virt the virt-CPU might get preempted. So do_nanosleep() wouldn't enter freezable_schedule() but cancel the timer which is still running and wait for it via hrtimer_wait_for_timer(). Then wait_event()/might_sleep() would complain that it is invoked with state != TASK_RUNNING. This isn't a problem since it would be reset to TASK_RUNNING later anyway and we don't rely on the previous state.
Move the state update to TASK_RUNNING before hrtimer_cancel() so there are no complains from might_sleep() about wrong state. Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- kernel/time/hrtimer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index bf0ec3fbbe797..851b2134e77f4 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1785,12 +1785,12 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod if (likely(t->task)) freezable_schedule(); + __set_current_state(TASK_RUNNING); hrtimer_cancel(&t->timer); mode = HRTIMER_MODE_ABS; } while (t->task && !signal_pending(current)); - __set_current_state(TASK_RUNNING); if (!t->task) return 0; -- 2.20.0.rc2
