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Groups > linux.kernel > #1638438

Re: [patch] fs, epoll: short circuit fetching events if thread has been killed

From Andrew Morton <akpm@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [patch] fs, epoll: short circuit fetching events if thread has been killed
Date 2017-05-10 01:10 +0200
Message-ID <tFmqu-8sO-7@gated-at.bofh.it> (permalink)
References <tDcOB-4jz-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, 3 May 2017 17:22:53 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:

> We've encountered zombies that are waiting for a thread to exit that are
> looping in ep_poll() almost endlessly although there is a pending SIGKILL
> as a result of a group exit.
> 
> This happens because we always find ep_events_available() and fetch more
> events and never are able to check for signal_pending() that would break
> from the loop and return -EINTR.
> 
> Special case fatal signals and break immediately to guarantee that we
> loop to fetch more events and delay making a timely exit.
> 
> It would also be possible to simply move the check for signal_pending()
> higher than checking for ep_events_available(), but there have been no
> reports of delayed signal handling other than SIGKILL preventing zombies
> from exiting that would be fixed by this.

Any thoughts on the priority of this?  -stable?  If so, why?

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Thread

[patch] fs, epoll: short circuit fetching events if thread has been  killed David Rientjes <rientjes@google.com> - 2017-05-04 02:30 +0200
  Re: [patch] fs, epoll: short circuit fetching events if thread has  been killed Andrew Morton <akpm@linux-foundation.org> - 2017-05-10 01:10 +0200
    Re: [patch] fs, epoll: short circuit fetching events if thread has  been killed David Rientjes <rientjes@google.com> - 2017-05-10 02:10 +0200
  Re: [patch] fs, epoll: short circuit fetching events if thread has  been killed Michal Hocko <mhocko@kernel.org> - 2017-05-10 15:10 +0200

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