If thread is preempted before calling set_current_state(TASK_INTERRUPTIBLE), and the other thread set the condition followed with wake_up_process. After that when this thread is re-scheduled, calling set_current_state to set itself as state TASK_INTERRUPTIBLE, if it is preempted again after that and before __set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem.
To solve this problem, using preempt_disable() to bound the operaion that setting the task state and the conditions(set by the wake thread) validation. Signed-off-by: Libin <[email protected]> --- kernel/hrtimer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 383319b..a7845ba 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1539,14 +1539,18 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod { hrtimer_init_sleeper(t, current); + preempt_disable(); do { set_current_state(TASK_INTERRUPTIBLE); hrtimer_start_expires(&t->timer, mode); if (!hrtimer_active(&t->timer)) t->task = NULL; - if (likely(t->task)) + if (likely(t->task)) { + preempt_enable(); freezable_schedule(); + preempt_disable(); + } hrtimer_cancel(&t->timer); mode = HRTIMER_MODE_ABS; @@ -1554,6 +1558,7 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod } while (t->task && !signal_pending(current)); __set_current_state(TASK_RUNNING); + preempt_enable(); return t->task == NULL; } -- 1.8.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
