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SubjectRe: net/sched: latent livelock in dev_deactivate_many() due to yield() usage
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On Wed, 2017-04-05 at 17:31 -0700, Stephen Hemminger wrote:
> On Sun, 02 Apr 2017 06:28:41 +0200
> Mike Galbraith <efault@gmx.de> wrote:
>
> > Livelock can be triggered by setting kworkers to SCHED_FIFO, then
> > suspend/resume.. you come back from sleepy-land with a spinning
> > kworker. For whatever reason, I can only do that with an enterprise
> > like config, my standard config refuses to play, but no matter, it's
> > "Typical broken usage".
> >
> > (yield() should be rendered dead)
>
> The kernel is not normally built to have kworkers run at SCHED_FIFO.
> The user has do some action to alter the process priorities.
>
> I classify this as user error. We don't support killing kworker threads
> either.

We'll have to agree to disagree on that. I assert that any thread that
must run as SCHED_OTHER in order to be safe is in fact broken.

-Mike

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