Re: [PATCH RT v2] Fix a lockup in wait_for_completion() and friends
From: Sebastian Andrzej Siewior
Date: Fri May 10 2019 - 06:34:47 EST
On 2019-05-09 14:33:20 [-0500], minyard@xxxxxxx wrote:
> From: Corey Minyard <cminyard@xxxxxxxxxx>
> The function call do_wait_for_common() has a race condition that
> can result in lockups waiting for completions. Adding the thread
> to (and removing the thread from) the wait queue for the completion
> is done outside the do loop in that function. However, if the thread
> is woken up, the swake_up_locked() function will delete the entry
> from the wait queue. If that happens and another thread sneaks
> in and decrements the done count in the completion to zero, the
> loop will go around again, but the thread will no longer be in the
> wait queue, so there is no way to wake it up.
applied, thank you.