diff options
| author | Arnd Bergmann <arnd@arndb.de> | 2010-06-01 22:53:06 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-08-10 13:47:43 -0700 |
| commit | 60af22d2ed490554cc92c8d0fed0b5b9cf687568 (patch) | |
| tree | 6c9d1b2d9b5c409dc6a38f26ed5b7ec0f37a041a /drivers/char/tty_ldisc.c | |
| parent | be1bc2889a4db4961ef69f47fb471ecae9f23ade (diff) | |
tty: reorder ldisc locking
We need to release the BTM in paste_selection() when
sleeping in tty_ldisc_ref_wait to avoid deadlocks
with tty_ldisc_enable.
In tty_set_ldisc, we now always grab the BTM before
taking the ldisc_mutex in order to avoid AB-BA
deadlocks between the two.
tty_ldisc_halt potentially blocks on a workqueue
function that takes the BTM, so we must release
the BTM before calling it.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/char/tty_ldisc.c')
| -rw-r--r-- | drivers/char/tty_ldisc.c | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c index 97681ffd6cb..0f494799da8 100644 --- a/drivers/char/tty_ldisc.c +++ b/drivers/char/tty_ldisc.c @@ -582,6 +582,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) tty_wait_until_sent(tty, 0); + tty_lock(); mutex_lock(&tty->ldisc_mutex); /* @@ -591,13 +592,13 @@ 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); + tty_lock(); mutex_lock(&tty->ldisc_mutex); } - tty_lock(); - set_bit(TTY_LDISC_CHANGING, &tty->flags); /* @@ -634,8 +635,8 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) flush_scheduled_work(); - mutex_lock(&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 */ @@ -782,7 +783,20 @@ void tty_ldisc_hangup(struct tty_struct *tty) * Avoid racing set_ldisc or tty_ldisc_release */ mutex_lock(&tty->ldisc_mutex); - tty_ldisc_halt(tty); + + /* + * this is like tty_ldisc_halt, but we need to give up + * the BTM before calling cancel_delayed_work_sync, + * which may need to wait for another function taking the BTM + */ + clear_bit(TTY_LDISC, &tty->flags); + tty_unlock(); + cancel_delayed_work_sync(&tty->buf.work); + mutex_unlock(&tty->ldisc_mutex); + + tty_lock(); + mutex_lock(&tty->ldisc_mutex); + /* At this point we have a closed ldisc and we want to reopen it. We could defer this to the next open but it means auditing a lot of other paths so this is @@ -853,8 +867,10 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) * race with the set_ldisc code path. */ + tty_unlock(); tty_ldisc_halt(tty); flush_scheduled_work(); + tty_lock(); mutex_lock(&tty->ldisc_mutex); /* |