diff options
Diffstat (limited to 'drivers/tty/tty_io.c')
| -rw-r--r-- | drivers/tty/tty_io.c | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index be18d60ddf4c..c6f4d711771b 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1465,7 +1465,6 @@ EXPORT_SYMBOL(tty_free_termios); * in use. It also gets called when setup of a device fails. * * Locking: - * tty_mutex - sometimes only * takes the file list lock internally when working on the list * of ttys that the driver keeps. * @@ -1526,17 +1525,16 @@ EXPORT_SYMBOL(tty_kref_put); * and decrement the refcount of the backing module. * * Locking: - * tty_mutex - sometimes only + * tty_mutex * takes the file list lock internally when working on the list * of ttys that the driver keeps. - * FIXME: should we require tty_mutex is held here ?? * */ static void release_tty(struct tty_struct *tty, int idx) { /* This should always be true but check for the moment */ WARN_ON(tty->index != idx); - + WARN_ON(!mutex_is_locked(&tty_mutex)); if (tty->ops->shutdown) tty->ops->shutdown(tty); tty_free_termios(tty); @@ -1708,6 +1706,9 @@ int tty_release(struct inode *inode, struct file *filp) * The closing flags are now consistent with the open counts on * both sides, and we've completed the last operation that could * block, so it's safe to proceed with closing. + * + * We must *not* drop the tty_mutex until we ensure that a further + * entry into tty_open can not pick up this tty. */ if (pty_master) { if (--o_tty->count < 0) { @@ -1759,12 +1760,13 @@ int tty_release(struct inode *inode, struct file *filp) } mutex_unlock(&tty_mutex); + tty_unlock(); + /* At this point the TTY_CLOSING flag should ensure a dead tty + cannot be re-opened by a racing opener */ /* check whether both sides are closing ... */ - if (!tty_closing || (o_tty && !o_tty_closing)) { - tty_unlock(); + if (!tty_closing || (o_tty && !o_tty_closing)) return 0; - } #ifdef TTY_DEBUG_HANGUP printk(KERN_DEBUG "%s: freeing tty structure...\n", __func__); @@ -1777,12 +1779,14 @@ int tty_release(struct inode *inode, struct file *filp) * The release_tty function takes care of the details of clearing * the slots and preserving the termios structure. */ + mutex_lock(&tty_mutex); release_tty(tty, idx); + mutex_unlock(&tty_mutex); /* Make this pty number available for reallocation */ if (devpts) devpts_kill_index(inode, idx); - tty_unlock(); + return 0; } |