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Commit 6e4e2f811bade330126d4029c88c831784a7efd9

Authored by Arnd Bergmann
Committed by David S. Miller
1 parent 60c2ce2b4f
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 2 changed files with 4 additions and 4 deletions Side-by-side Diff

drivers/net/hamradio/6pack.c
Diff comments   View file @ 6e4e2f8
... ... @@ -692,10 +692,10 @@
692 692 {
693 693 struct sixpack *sp;
694 694  
695   - write_lock(&disc_data_lock);
  695 + write_lock_bh(&disc_data_lock);
696 696 sp = tty->disc_data;
697 697 tty->disc_data = NULL;
698   - write_unlock(&disc_data_lock);
  698 + write_unlock_bh(&disc_data_lock);
699 699 if (!sp)
700 700 return;
701 701  
drivers/net/hamradio/mkiss.c
Diff comments   View file @ 6e4e2f8
... ... @@ -813,10 +813,10 @@
813 813 {
814 814 struct mkiss *ax;
815 815  
816   - write_lock(&disc_data_lock);
  816 + write_lock_bh(&disc_data_lock);
817 817 ax = tty->disc_data;
818 818 tty->disc_data = NULL;
819   - write_unlock(&disc_data_lock);
  819 + write_unlock_bh(&disc_data_lock);
820 820  
821 821 if (!ax)
822 822 return;