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    Subject[19/35] 6pack,mkiss: fix lock inconsistency
    2.6.33-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Arnd Bergmann <arnd@arndb.de>

    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 | 4 ++--
    drivers/net/hamradio/mkiss.c | 4 ++--
    2 files changed, 4 insertions(+), 4 deletions(-)

    --- a/drivers/net/hamradio/6pack.c
    +++ b/drivers/net/hamradio/6pack.c
    @@ -691,10 +691,10 @@ static void sixpack_close(struct tty_str
    {
    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;

    --- a/drivers/net/hamradio/mkiss.c
    +++ b/drivers/net/hamradio/mkiss.c
    @@ -812,10 +812,10 @@ static void mkiss_close(struct tty_struc
    {
    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;



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