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

From Cong Wang <xiyou.wangcong@gmail.com>
Newsgroups linux.kernel
Subject Re: net/sched: latent livelock in dev_deactivate_many() due to yield() usage
Date 2017-04-05 07:30 +0200
Message-ID <tsLG1-6OS-1@gated-at.bofh.it> (permalink)
References <trFjj-40B-3@gated-at.bofh.it> <tsFhf-2yy-13@gated-at.bofh.it> <tsJNT-5yF-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Tue, Apr 4, 2017 at 8:20 PM, Mike Galbraith <efault@gmx.de> wrote:
> -               while (some_qdisc_is_busy(dev))
> -                       yield();
> +               swait_event_timeout(swait, !some_qdisc_is_busy(dev), 1);
>  }

I don't see why this is an improvement even if I don't care about the
hardcoded timeout for now... Why the scheduler can make a better
decision with swait_event_timeout() than with cond_resched()?

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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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