pty: Lock the devpts bits privately

This is a private pty affair, we don't want to tangle it with the tty_lock
any more as we know all the other non tty locking is now handled by the vfs
so we too can move.

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

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index eeae7fa..5505ffc 100644 (file)
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -26,11 +26,13 @@
 #include <linux/bitops.h>
 #include <linux/devpts_fs.h>
 #include <linux/slab.h>
+#include <linux/mutex.h>
 
 
 #ifdef CONFIG_UNIX98_PTYS
 static struct tty_driver *ptm_driver;
 static struct tty_driver *pts_driver;
+static DEFINE_MUTEX(devpts_mutex);
 #endif
 
 static void pty_close(struct tty_struct *tty, struct file *filp)
@@ -54,8 +56,11 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
        if (tty->driver->subtype == PTY_TYPE_MASTER) {
                set_bit(TTY_OTHER_CLOSED, &tty->flags);
 #ifdef CONFIG_UNIX98_PTYS
-               if (tty->driver == ptm_driver)
+               if (tty->driver == ptm_driver) {
+                       mutex_lock(&devpts_mutex);
                        devpts_pty_kill(tty->link);
+                       mutex_unlock(&devpts_mutex);
+               }
 #endif
                tty_unlock();
                tty_vhangup(tty->link);
@@ -475,13 +480,17 @@ static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
  *     @idx: tty index
  *
  *     Look up a pty master device. Called under the tty_mutex for now.
- *     This provides our locking.
+ *     This provides our locking for the tty pointer.
  */
 
 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
                struct inode *pts_inode, int idx)
 {
-       struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
+       struct tty_struct *tty;
+
+       mutex_lock(&devpts_mutex);
+       tty = devpts_get_tty(pts_inode, idx);
+       mutex_unlock(&devpts_mutex);
        /* Master must be open before slave */
        if (!tty)
                return ERR_PTR(-EIO);
@@ -622,8 +631,10 @@ static int ptmx_open(struct inode *inode, struct file *filp)
        }
 
        mutex_lock(&tty_mutex);
-       tty_lock();
+       mutex_lock(&devpts_mutex);
        tty = tty_init_dev(ptm_driver, index);
+       mutex_unlock(&devpts_mutex);
+       tty_lock();
        mutex_unlock(&tty_mutex);
 
        if (IS_ERR(tty)) {