From: Arnd Bergmann <arnd@arndb.de>
Date: Sat, 2 Jul 2011 00:30:00 +0000 (-0700)
Subject: 6pack,mkiss: fix lock inconsistency
X-Git-Tag: v3.0-rc7~41^2~21
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6e4e2f811bade330126d4029c88c831784a7efd9;p=pandora-kernel.git

6pack,mkiss: fix lock inconsistency

Lockdep found a locking inconsistency in the mkiss_close function:

> kernel: [ INFO: inconsistent lock state ]
> kernel: 2.6.39.1 #3
> kernel: ---------------------------------
> kernel: inconsistent {IN-SOFTIRQ-R} -> {SOFTIRQ-ON-W} usage.
> kernel: ax25ipd/2813 [HC0[0]:SC0[0]:HE1:SE1] takes:
> kernel: (disc_data_lock){+++?.-}, at: [<ffffffffa018552b>] mkiss_close+0x1b/0x90 [mkiss]
> kernel: {IN-SOFTIRQ-R} state was registered at:

The message hints that disc_data_lock is aquired with softirqs disabled,
but does not itself disable softirqs, which can in rare circumstances
lead to a deadlock.
The same problem is present in the 6pack driver, this patch fixes both
by using write_lock_bh instead of write_lock.

Reported-by: Bernard F6BVP <f6bvp@free.fr>
Tested-by: Bernard F6BVP <f6bvp@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ralf Baechle<ralf@linux-mips.org>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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