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/time/alarmtimer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c index eec50fc..624f2ed 100644 --- a/kernel/time/alarmtimer.c +++ b/kernel/time/alarmtimer.c @@ -629,16 +629,21 @@ static enum alarmtimer_restart alarmtimer_nsleep_wakeup(struct alarm *alarm, static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp) { alarm->data = (void *)current; + preempt_disable(); do { set_current_state(TASK_INTERRUPTIBLE); alarm_start(alarm, absexp); - if (likely(alarm->data)) + if (likely(alarm->data)) { + preempt_enable(); schedule(); + preempt_disable(); + } alarm_cancel(alarm); } while (alarm->data && !signal_pending(current)); __set_current_state(TASK_RUNNING); + preempt_enable(); return (alarm->data == 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/
