6pack,mkiss: fix lock inconsistency
commit06ce414d4a0811a979a82cddc3e429e6bd704c98
authorArnd Bergmann <arnd@arndb.de>
Sat, 2 Jul 2011 00:30:00 +0000 (1 17:30 -0700)
committerGreg Kroah-Hartman <gregkh@suse.de>
Wed, 13 Jul 2011 03:29:25 +0000 (13 05:29 +0200)
tree9ff0ef50bf725b2668d164fa713910f3e3d8bdc6
parentd2c7e885624f03cdbba80f124096e5073156969e
6pack,mkiss: fix lock inconsistency

commit 6e4e2f811bade330126d4029c88c831784a7efd9 upstream.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
drivers/net/hamradio/6pack.c
drivers/net/hamradio/mkiss.c