Re: net/sched: latent livelock in dev_deactivate_many() due to yield() usage

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From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: net/sched: latent livelock in dev_deactivate_many() due to yield() usage
Date	Thu, 06 Apr 2017 12:30:03 +0200
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X-Original-To	Stephen Hemminger <stephen@networkplumber.org>
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X-Original-Cc	Mike Galbraith <efault@gmx.de>, netdev <netdev@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>
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On Wed, Apr 05, 2017 at 05:31:05PM -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.

PI can boost anybody to FIFO, all you need is to be holding a lock.

Thread

net/sched: latent livelock in dev_deactivate_many() due to yield()  usage Mike Galbraith <efault@gmx.de> - 2017-04-02 06:30 +0200
  Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-05 00:40 +0200
    Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Mike Galbraith <efault@gmx.de> - 2017-04-05 05:30 +0200
      Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-05 07:30 +0200
        Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Mike Galbraith <efault@gmx.de> - 2017-04-05 08:20 +0200
          Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Cong Wang <xiyou.wangcong@gmail.com> - 2017-04-06 02:00 +0200
            Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Mike Galbraith <efault@gmx.de> - 2017-04-06 03:10 +0200
        Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Peter Zijlstra <peterz@infradead.org> - 2017-04-06 12:30 +0200
  Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Stephen Hemminger <stephen@networkplumber.org> - 2017-04-06 02:40 +0200
    Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Mike Galbraith <efault@gmx.de> - 2017-04-06 03:30 +0200
    Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Peter Zijlstra <peterz@infradead.org> - 2017-04-06 12:30 +0200
      Re: net/sched: latent livelock in dev_deactivate_many() due to  yield() usage Peter Zijlstra <peterz@infradead.org> - 2017-04-06 13:10 +0200

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