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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAM_iQpVTmDfATw1HMPE9NnRBNnhgidz+UZOQDqyeq2uo0=c-+g@mail.gmail.com>
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()?