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From: Josh Boyer <jwboyer@redhat.com>
Subject: Re: [PATCH] epoll: Fix spurious lockdep warnings.
Date: Tue, 9 Aug 2011 11:11:55 -0400
Message-ID: <20110809151154.GA2411@zod.bos.redhat.com>
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Cc: Paul Bolle <pebolle@tiscali.nl>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org,
	Davide Libenzi <davidel@xmailserver.org>,
	Nelson Elhage <nelhage@nelhage.com>
To: Nelson Elhage <nelhage@ksplice.com>
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On Sat, Jul 30, 2011 at 06:30:22PM -0400, Nelson Elhage wrote:
> epoll can acquire multiple ep->mutex on multiple "struct eventpoll"s
> at once in the case where one epoll fd is monitoring another epoll
> fd. This is perfectly OK, since we're careful about the lock ordering,
> but causes spurious lockdep warnings. Annotate the recursion using
> mutex_lock_nested, and add a comment explaining the nesting rules for
> good measure.
> 
> Reported-by: Paul Bolle <pebolle@tiscali.nl>
> Signed-off-by: Nelson Elhage <nelhage@nelhage.com>

We were seeing lockdep warnings for this in rawhide until I applied the
patch.  Would it be possible to get it into 3.1 still?

josh