tty: Don't take tty_mutex for tty count changes

Holding tty_mutex is no longer required to serialize changes to
the tty_count or to prevent concurrent opens of closing ttys;
tty_lock() is sufficient.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index ea8c6cae8d1254fc5b0f9a53976b3e0da8cdd00f..e59de81c39a922bc4a7bce42fa44a6a14e173a80 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1804,10 +1804,6 @@ int tty_release(struct inode *inode, struct file *filp)
         * each iteration we avoid any problems.
         */
        while (1) {
-               /* Guard against races with tty->count changes elsewhere and
-                  opens on /dev/tty */
-
-               mutex_lock(&tty_mutex);
                tty_lock_pair(tty, o_tty);
                tty_closing = tty->count <= 1;
                o_tty_closing = o_tty &&
@@ -1840,7 +1836,6 @@ int tty_release(struct inode *inode, struct file *filp)
                printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
                                __func__, tty_name(tty, buf));
                tty_unlock_pair(tty, o_tty);
-               mutex_unlock(&tty_mutex);
                schedule();
        }
 
@@ -1891,7 +1886,6 @@ int tty_release(struct inode *inode, struct file *filp)
                read_unlock(&tasklist_lock);
        }
 
-       mutex_unlock(&tty_mutex);
        tty_unlock_pair(tty, o_tty);
        /* At this point, the tty->count == 0 should ensure a dead tty
           cannot be re-opened by a racing opener */