netdev - Re: net/sched: latent livelock in dev_deactivate

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Date:   Tue, 4 Apr 2017 22:25:19 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Mike Galbraith <efault@....de>
Cc:     netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: net/sched: latent livelock in dev_deactivate_many() due to
 yield() usage

On Tue, Apr 4, 2017 at 8:20 PM, Mike Galbraith <efault@....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()?