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Date: Thu, 30 Nov 2017 12:50:50 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Ingo Molnar <mingo@redhat.com>,
        eter Zijlstra <peterz@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: waitqueue lockdep annotation
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On Thu, 30 Nov 2017 06:20:35 -0800 Christoph Hellwig <hch@lst.de> wrote:

> Hi all,
> 
> this series adds a strategic lockdep_assert_held to __wake_up_common
> to ensure callers really do hold the wait_queue_head lock when calling
> the unlocked wake_up variants.  It turns out epoll did not do this
> for a fairly common path (hit all the time by systemd during bootup),
> so the second patch fixed this instance as well.

What are the runtime effects of the epoll bug?