From: Joseph Qi <joseph.qi@huawei.com>
Date: Tue, 22 Sep 2015 21:59:20 +0000 (-0700)
Subject: ocfs2/dlm: fix deadlock when dispatch assert master
X-Git-Tag: v3.2.72~21
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=307c6c27d5de3b44965cdba2a69e1d5f922a01c1;p=pandora-kernel.git

ocfs2/dlm: fix deadlock when dispatch assert master

commit 012572d4fc2e4ddd5c8ec8614d51414ec6cae02a upstream.

The order of the following three spinlocks should be:
dlm_domain_lock < dlm_ctxt->spinlock < dlm_lock_resource->spinlock

But dlm_dispatch_assert_master() is called while holding
dlm_ctxt->spinlock and dlm_lock_resource->spinlock, and then it calls
dlm_grab() which will take dlm_domain_lock.

Once another thread (for example, dlm_query_join_handler) has already
taken dlm_domain_lock, and tries to take dlm_ctxt->spinlock deadlock
happens.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: "Junxiao Bi" <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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