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Subject[PATCH 2/3] pty: Lock the devpts bits privately
Date
From: Alan Cox <alan@linux.intel.com>

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>
---
drivers/tty/pty.c | 19 +++++++++++++++----
1 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index eeae7fa..5505ffc 100644
--- 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)) {


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