diff options
Diffstat (limited to 'drivers/char/tty_ldisc.c')
| -rw-r--r-- | drivers/char/tty_ldisc.c | 43 |
1 files changed, 30 insertions, 13 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c index 500e740..412f977 100644 --- a/drivers/char/tty_ldisc.c +++ b/drivers/char/tty_ldisc.c @@ -440,6 +440,8 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) * * A helper opening method. Also a convenient debugging and check * point. + * + * Locking: always called with BTM already held. */ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) @@ -447,10 +449,9 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); if (ld->ops->open) { int ret; - /* BKL here locks verus a hangup event */ - lock_kernel(); + /* BTM here locks versus a hangup event */ + WARN_ON(!tty_locked()); ret = ld->ops->open(tty); - unlock_kernel(); return ret; } return 0; @@ -553,7 +554,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (IS_ERR(new_ldisc)) return PTR_ERR(new_ldisc); - lock_kernel(); + tty_lock(); /* * We need to look at the tty locking here for pty/tty pairs * when both sides try to change in parallel. @@ -567,12 +568,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) */ if (tty->ldisc->ops->num == ldisc) { - unlock_kernel(); + tty_unlock(); tty_ldisc_put(new_ldisc); return 0; } - unlock_kernel(); + tty_unlock(); /* * Problem: What do we do if this blocks ? * We could deadlock here @@ -580,6 +581,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) tty_wait_until_sent(tty, 0); + tty_lock(); mutex_lock(&tty->ldisc_mutex); /* @@ -589,13 +591,13 @@ 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); } - lock_kernel(); - set_bit(TTY_LDISC_CHANGING, &tty->flags); /* @@ -607,7 +609,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) o_ldisc = tty->ldisc; - unlock_kernel(); + tty_unlock(); /* * Make sure we don't change while someone holds a * reference to the line discipline. The TTY_LDISC bit @@ -632,15 +634,15 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) flush_scheduled_work(); + tty_lock(); mutex_lock(&tty->ldisc_mutex); - lock_kernel(); 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 */ clear_bit(TTY_LDISC_CHANGING, &tty->flags); mutex_unlock(&tty->ldisc_mutex); tty_ldisc_put(new_ldisc); - unlock_kernel(); + tty_unlock(); return -EIO; } @@ -682,7 +684,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) if (o_work) schedule_delayed_work(&o_tty->buf.work, 1); mutex_unlock(&tty->ldisc_mutex); - unlock_kernel(); + tty_unlock(); return retval; } @@ -780,7 +782,20 @@ 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 @@ -851,8 +866,10 @@ 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); /* |