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wait_event()\wake_up order fails?

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  wait_event()\wake_up order fails? Muni Sekhar <munisekharrms@gmail.com> - 2016-06-16 14:50 +0200

#1424021 — wait_event()\wake_up order fails?

Hi All,


I have a kernel thread THREAD_A and it waits for an event by calling
wait_event() API.

Other thread THREAD_B wakes up the THREAD_A by calling wake_up() API.

In a concurrent execution, what if the wake_up() is called before
THREAD_A entering into TASK_UNINTERRUPTIBLE sleep?


I have noticed in running long soak test, THREAD_A enters into
TASK_UNINTERRUPTIBLE sleep and THREAD_B’s wake_up() not able to wake
the THREAD_A, what might be the reason for this?


I would like to know in which scenario wake_up() fails to wake the
sleeping thread?



-- 
Thanks,
Sekhar

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