6pack,mkiss: fix lock inconsistency
authorArnd Bergmann <arnd@arndb.de>
Sat, 2 Jul 2011 00:30:00 +0000 (17:30 -0700)
committerDavid S. Miller <davem@davemloft.net>
Sat, 2 Jul 2011 00:30:00 +0000 (17:30 -0700)
commit6e4e2f811bade330126d4029c88c831784a7efd9
tree03d365ae386b9a8f43c24483eb0455a73a96bf48
parent60c2ce2b4facf28f569115a55e1f479eb12bd0f1
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>
drivers/net/hamradio/6pack.c
drivers/net/hamradio/mkiss.c