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tty_ldisc: Fix BUG() on hangup 

A kernel BUG when bluetooth rfcomm connection drop while the associated
serial port is open is sometime triggered.

It seems that the line discipline can disappear between the
tty_ldisc_put and tty_ldisc_get. This patch fall back to the N_TTY line
discipline if the previous discipline is not available anymore.

Signed-off-by: Philippe Retornaz <philippe.retornaz@epfl.ch>
Acked-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Philippe Rétornaz 2010-10-27 17:13:21 +02:00 committed by Greg Kroah-Hartman
parent 100eeae2c5
commit 1c95ba1e1d
1 changed files with 13 additions and 7 deletions
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20
drivers/tty/tty_ldisc.c
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@ -743,9 +743,12 @@ static void tty_reset_termios(struct tty_struct *tty)
* state closed
*/
static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
{
struct tty_ldisc *ld;
struct tty_ldisc *ld = tty_ldisc_get(ldisc);
if (IS_ERR(ld))
return -1;
tty_ldisc_close(tty, tty->ldisc);
tty_ldisc_put(tty->ldisc);
@ -753,10 +756,10 @@ static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
/*
* Switch the line discipline back
*/
ld = tty_ldisc_get(ldisc);
BUG_ON(IS_ERR(ld));
tty_ldisc_assign(tty, ld);
tty_set_termios_ldisc(tty, ldisc);
return 0;
}
/**
@ -831,13 +834,16 @@ void tty_ldisc_hangup(struct tty_struct *tty)
a FIXME */
if (tty->ldisc) { /* Not yet closed */
if (reset == 0) {
tty_ldisc_reinit(tty, tty->termios->c_line);
err = tty_ldisc_open(tty, tty->ldisc);
if (!tty_ldisc_reinit(tty, tty->termios->c_line))
err = tty_ldisc_open(tty, tty->ldisc);
else
err = 1;
}
/* If the re-open fails or we reset then go to N_TTY. The
N_TTY open cannot fail */
if (reset || err) {
tty_ldisc_reinit(tty, N_TTY);
BUG_ON(tty_ldisc_reinit(tty, N_TTY));
WARN_ON(tty_ldisc_open(tty, tty->ldisc));
}
tty_ldisc_enable(tty);