Re: [PATCH RT v2] Fix a lockup in wait_for_completion() and friends

From: Peter Zijlstra
Date: Tue May 14 2019 - 07:37:50 EST

On Tue, May 14, 2019 at 11:12:19AM +0200, Sebastian Andrzej Siewior wrote:
> On 2019-05-14 10:43:56 [+0200], Peter Zijlstra wrote:
> > Now.. that will fix it, but I think it is also wrong.
> >
> > The problem being that it violates FIFO, something that might be more
> > important on -RT than elsewhere.
> Wouldn't -RT be more about waking the task with the highest priority
> instead the one that waited the longest?

Possibly, but that's a far larger patch. Also, even with that
completions do not avoid inversions and thus don't really make nice RT
primitives anyway.