From f309532bf3e1cc1b787403d84e3039812a7dbe50 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 2 Jun 2012 15:21:43 -0700 Subject: tty: Revert the tty locking series, it needs more work This reverts the tty layer change to use per-tty locking, because it's not correct yet, and fixing it will require some more deep surgery. The main revert is d29f3ef39be4 ("tty_lock: Localise the lock"), but there are several smaller commits that built upon it, they also get reverted here. The list of reverted commits is: fde86d310886 - tty: add lockdep annotations 8f6576ad476b - tty: fix ldisc lock inversion trace d3ca8b64b97e - pty: Fix lock inversion b1d679afd766 - tty: drop the pty lock during hangup abcefe5fc357 - tty/amiserial: Add missing argument for tty_unlock() fd11b42e3598 - cris: fix missing tty arg in wait_event_interruptible_tty call d29f3ef39be4 - tty_lock: Localise the lock The revert had a trivial conflict in the 68360serial.c staging driver that got removed in the meantime. Signed-off-by: Linus Torvalds --- drivers/tty/tty_ldisc.c | 67 +++++++++++++++++++++---------------------------- 1 file changed, 29 insertions(+), 38 deletions(-) (limited to 'drivers/tty/tty_ldisc.c') diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index ba8be396a621..9911eb6b34cd 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -568,7 +568,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (IS_ERR(new_ldisc)) return PTR_ERR(new_ldisc); - tty_lock(tty); + tty_lock(); /* * We need to look at the tty locking here for pty/tty pairs * when both sides try to change in parallel. @@ -582,12 +582,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) */ if (tty->ldisc->ops->num == ldisc) { - tty_unlock(tty); + tty_unlock(); tty_ldisc_put(new_ldisc); return 0; } - tty_unlock(tty); + tty_unlock(); /* * Problem: What do we do if this blocks ? * We could deadlock here @@ -595,7 +595,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) tty_wait_until_sent(tty, 0); - tty_lock(tty); + tty_lock(); mutex_lock(&tty->ldisc_mutex); /* @@ -605,10 +605,10 @@ 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(tty); + tty_unlock(); wait_event(tty_ldisc_wait, test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); - tty_lock(tty); + tty_lock(); mutex_lock(&tty->ldisc_mutex); } @@ -623,7 +623,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) o_ldisc = tty->ldisc; - tty_unlock(tty); + tty_unlock(); /* * Make sure we don't change while someone holds a * reference to the line discipline. The TTY_LDISC bit @@ -650,7 +650,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) retval = tty_ldisc_wait_idle(tty, 5 * HZ); - tty_lock(tty); + tty_lock(); mutex_lock(&tty->ldisc_mutex); /* handle wait idle failure locked */ @@ -665,7 +665,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) clear_bit(TTY_LDISC_CHANGING, &tty->flags); mutex_unlock(&tty->ldisc_mutex); tty_ldisc_put(new_ldisc); - tty_unlock(tty); + tty_unlock(); return -EIO; } @@ -708,7 +708,7 @@ enable: if (o_work) schedule_work(&o_tty->buf.work); mutex_unlock(&tty->ldisc_mutex); - tty_unlock(tty); + tty_unlock(); return retval; } @@ -816,11 +816,11 @@ void tty_ldisc_hangup(struct tty_struct *tty) * need to wait for another function taking the BTM */ clear_bit(TTY_LDISC, &tty->flags); - tty_unlock(tty); + tty_unlock(); cancel_work_sync(&tty->buf.work); mutex_unlock(&tty->ldisc_mutex); retry: - tty_lock(tty); + tty_lock(); mutex_lock(&tty->ldisc_mutex); /* At this point we have a closed ldisc and we want to @@ -831,7 +831,7 @@ retry: if (atomic_read(&tty->ldisc->users) != 1) { char cur_n[TASK_COMM_LEN], tty_n[64]; long timeout = 3 * HZ; - tty_unlock(tty); + tty_unlock(); while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) { timeout = MAX_SCHEDULE_TIMEOUT; @@ -894,23 +894,6 @@ int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) tty_ldisc_enable(tty); return 0; } - -static void tty_ldisc_kill(struct tty_struct *tty) -{ - mutex_lock(&tty->ldisc_mutex); - /* - * Now kill off the ldisc - */ - tty_ldisc_close(tty, tty->ldisc); - tty_ldisc_put(tty->ldisc); - /* Force an oops if we mess this up */ - tty->ldisc = NULL; - - /* Ensure the next open requests the N_TTY ldisc */ - tty_set_termios_ldisc(tty, N_TTY); - mutex_unlock(&tty->ldisc_mutex); -} - /** * tty_ldisc_release - release line discipline * @tty: tty being shut down @@ -929,19 +912,27 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) * race with the set_ldisc code path. */ - tty_unlock_pair(tty, o_tty); + tty_unlock(); tty_ldisc_halt(tty); tty_ldisc_flush_works(tty); - if (o_tty) { - tty_ldisc_halt(o_tty); - tty_ldisc_flush_works(o_tty); - } - tty_lock_pair(tty, o_tty); + tty_lock(); + mutex_lock(&tty->ldisc_mutex); + /* + * Now kill off the ldisc + */ + tty_ldisc_close(tty, tty->ldisc); + tty_ldisc_put(tty->ldisc); + /* Force an oops if we mess this up */ + tty->ldisc = NULL; + + /* Ensure the next open requests the N_TTY ldisc */ + tty_set_termios_ldisc(tty, N_TTY); + mutex_unlock(&tty->ldisc_mutex); - tty_ldisc_kill(tty); + /* This will need doing differently if we need to lock */ if (o_tty) - tty_ldisc_kill(o_tty); + tty_ldisc_release(o_tty, NULL); /* And the memory resources remaining (buffers, termios) will be disposed of when the kref hits zero */ -- cgit v1.2.3