From: Takashi Iwai Date: Wed, 3 Feb 2016 07:32:44 +0000 (+0100) Subject: ALSA: seq: Fix lockdep warnings due to double mutex locks X-Git-Tag: v3.2.78~29 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=96c6b772f57fa832c1d6f3fd9ba1a70ec0a0d4a6;p=pandora-kernel.git ALSA: seq: Fix lockdep warnings due to double mutex locks commit 7f0973e973cd74aa40747c9d38844560cd184ee8 upstream. The port subscription code uses double mutex locks for source and destination ports, and this may become racy once when wrongly set up. It leads to lockdep warning splat, typically triggered by fuzzer like syzkaller, although the actual deadlock hasn't been seen, so far. This patch simplifies the handling by reducing to two single locks, so that no lockdep warning will be trigger any longer. By splitting to two actions, a still-in-progress element shall be added in one list while handling another. For ignoring this element, a new check is added in deliver_to_subscribers(). Along with it, the code to add/remove the subscribers list element was cleaned up and refactored. BugLink: http://lkml.kernel.org/r/CACT4Y+aKQXV7xkBW9hpQbzaDO7LrUvohxWh-UwMxXjDy-yBD=A@mail.gmail.com Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed