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path: root/drivers/tty/pty.c
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Diffstat (limited to 'drivers/tty/pty.c')
-rw-r--r--drivers/tty/pty.c40
1 files changed, 28 insertions, 12 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index eeae7fafe9a7..59af3945ea85 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)
@@ -45,6 +47,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
wake_up_interruptible(&tty->read_wait);
wake_up_interruptible(&tty->write_wait);
tty->packet = 0;
+ /* Review - krefs on tty_link ?? */
if (!tty->link)
return;
tty->link->packet = 0;
@@ -54,12 +57,15 @@ 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_unlock(tty);
tty_vhangup(tty->link);
- tty_lock();
+ tty_lock(tty);
}
}
@@ -475,13 +481,17 @@ 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);
@@ -613,24 +623,29 @@ static int ptmx_open(struct inode *inode, struct file *filp)
return retval;
/* find a device that is not in use. */
- tty_lock();
+ mutex_lock(&devpts_mutex);
index = devpts_new_index(inode);
- tty_unlock();
if (index < 0) {
retval = index;
goto err_file;
}
+ mutex_unlock(&devpts_mutex);
+
mutex_lock(&tty_mutex);
- tty_lock();
+ mutex_lock(&devpts_mutex);
tty = tty_init_dev(ptm_driver, index);
- mutex_unlock(&tty_mutex);
if (IS_ERR(tty)) {
retval = PTR_ERR(tty);
goto out;
}
+ /* The tty returned here is locked so we can safely
+ drop the mutex */
+ mutex_unlock(&devpts_mutex);
+ mutex_unlock(&tty_mutex);
+
set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
tty_add_file(tty, filp);
@@ -643,16 +658,17 @@ static int ptmx_open(struct inode *inode, struct file *filp)
if (retval)
goto err_release;
- tty_unlock();
+ tty_unlock(tty);
return 0;
err_release:
- tty_unlock();
+ tty_unlock(tty);
tty_release(inode, filp);
return retval;
out:
+ mutex_unlock(&tty_mutex);
devpts_kill_index(inode, index);
- tty_unlock();
err_file:
+ mutex_unlock(&devpts_mutex);
tty_free_file(filp);
return retval;
}