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Subject[PATCH 13/13] tty: turn ldisc_mutex into a regular mutex
Date
This fixes the lock order of the BTM and
ldisc_mutex so that we never take the BTM
while holding ldisc_mutex, which means
we no longer have to use mutex_lock_tty
when getting ldisc_mutex.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
drivers/char/tty_io.c | 2 +-
drivers/char/tty_ldisc.c | 15 ++++++++-------
2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 4e16b34..80178cc 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1289,7 +1289,7 @@ static int tty_reopen(struct tty_struct *tty)
tty->count++;
tty->driver = driver; /* N.B. why do this every time?? */

- mutex_lock_tty_on(&tty->ldisc_mutex);
+ mutex_lock(&tty->ldisc_mutex);
WARN_ON(!test_bit(TTY_LDISC, &tty->flags));
mutex_unlock(&tty->ldisc_mutex);

diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index 0c0e935..dda31b0 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -598,7 +598,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

tty_wait_until_sent(tty, 0);

- mutex_lock_tty_off(&tty->ldisc_mutex);
+ tty_lock();
+ mutex_lock(&tty->ldisc_mutex);

/*
* We could be midstream of another ldisc change which has
@@ -607,13 +608,13 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
mutex_unlock(&tty->ldisc_mutex);
+ tty_unlock();
wait_event(tty_ldisc_wait,
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
- mutex_lock_tty_off(&tty->ldisc_mutex);
+ tty_lock();
+ mutex_lock(&tty->ldisc_mutex);
}

- tty_lock();
-
set_bit(TTY_LDISC_CHANGING, &tty->flags);

/*
@@ -650,8 +651,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

flush_scheduled_work();

- mutex_lock_tty_off(&tty->ldisc_mutex);
tty_lock();
+ mutex_lock(&tty->ldisc_mutex);
if (test_bit(TTY_HUPPED, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
the ldisc data and closed the ldisc down */
@@ -797,7 +798,7 @@ void tty_ldisc_hangup(struct tty_struct *tty)
*
* Avoid racing set_ldisc or tty_ldisc_release
*/
- mutex_lock_tty_on(&tty->ldisc_mutex);
+ mutex_lock(&tty->ldisc_mutex);
tty_ldisc_halt(tty);
/* At this point we have a closed ldisc and we want to
reopen it. We could defer this to the next open but
@@ -873,7 +874,7 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
tty_unlock();
flush_scheduled_work();
tty_lock();
- mutex_lock_tty_on(&tty->ldisc_mutex);
+ mutex_lock(&tty->ldisc_mutex);
/*
* Now kill off the ldisc
*/
--
1.7.0.4


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