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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>
This commit is contained in:
Arnd Bergmann 2011-07-01 17:30:00 -07:00 committed by David S. Miller
parent 60c2ce2b4f
commit 6e4e2f811b
2 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/net/hamradio/6pack.c
View File

@ -692,10 +692,10 @@ static void sixpack_close(struct tty_struct *tty)
{
struct sixpack *sp;
write_lock(&disc_data_lock);
write_lock_bh(&disc_data_lock);
sp = tty->disc_data;
tty->disc_data = NULL;
write_unlock(&disc_data_lock);
write_unlock_bh(&disc_data_lock);
if (!sp)
return;

4
drivers/net/hamradio/mkiss.c
View File

@ -813,10 +813,10 @@ static void mkiss_close(struct tty_struct *tty)
{
struct mkiss *ax;
write_lock(&disc_data_lock);
write_lock_bh(&disc_data_lock);
ax = tty->disc_data;
tty->disc_data = NULL;
write_unlock(&disc_data_lock);
write_unlock_bh(&disc_data_lock);
if (!ax)
return;