tty: Wait interruptibly for tty lock on reopen

peterhurley · gregkh · commit 0bfd464d3fdd · 2016-01-26T23:17:54.000-08:00
Allow a signal to interrupt the wait for a tty reopen; eg., if
the tty has starting final close and is waiting for the device to
drain.

Signed-off-by: Peter Hurley &lt;peter@hurleysoftware.com&gt;
Cc: stable &lt;stable@vger.kernel.org&gt; # 4.4
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
@@ -2065,7 +2065,12 @@ static int tty_open(struct inode *inode, struct file *filp)
 
 		if (tty) {
 			mutex_unlock(&tty_mutex);
-			tty_lock(tty);
+			retval = tty_lock_interruptible(tty);
+			if (retval) {
+				if (retval == -EINTR)
+					retval = -ERESTARTSYS;
+				goto err_unref;
+			}
 			/* safe to drop the kref from tty_driver_lookup_tty() */
 			tty_kref_put(tty);
 			retval = tty_reopen(tty);
@@ -2152,6 +2157,7 @@ static int tty_open(struct inode *inode, struct file *filp)
 	return 0;
 err_unlock:
 	mutex_unlock(&tty_mutex);
+err_unref:
 	/* after locks to avoid deadlock */
 	if (!IS_ERR_OR_NULL(driver))
 		tty_driver_kref_put(driver);
diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
@@ -19,6 +19,14 @@ void __lockfunc tty_lock(struct tty_struct *tty)
 }
 EXPORT_SYMBOL(tty_lock);
 
+int tty_lock_interruptible(struct tty_struct *tty)
+{
+	if (WARN(tty->magic != TTY_MAGIC, "L Bad %p\n", tty))
+		return -EIO;
+	tty_kref_get(tty);
+	return mutex_lock_interruptible(&tty->legacy_mutex);
+}
+
 void __lockfunc tty_unlock(struct tty_struct *tty)
 {
 	if (WARN(tty->magic != TTY_MAGIC, "U Bad %p\n", tty))
diff --git a/include/linux/tty.h b/include/linux/tty.h
@@ -649,6 +649,7 @@ extern long vt_compat_ioctl(struct tty_struct *tty,
 /* tty_mutex.c */
 /* functions for preparation of BKL removal */
 extern void __lockfunc tty_lock(struct tty_struct *tty);
+extern int  tty_lock_interruptible(struct tty_struct *tty);
 extern void __lockfunc tty_unlock(struct tty_struct *tty);
 extern void __lockfunc tty_lock_slave(struct tty_struct *tty);
 extern void __lockfunc tty_unlock_slave(struct tty_struct *tty);

Original file line number	Diff line number	Diff line change
`@@ -19,6 +19,14 @@ void __lockfunc tty_lock(struct tty_struct *tty)`
`19`	`19`	`}`
`20`	`20`	`EXPORT_SYMBOL(tty_lock);`
`21`	`21`
	`22`	`+int tty_lock_interruptible(struct tty_struct *tty)`
	`23`	`+{`
	`24`	`+ if (WARN(tty->magic != TTY_MAGIC, "L Bad %p\n", tty))`
	`25`	`+ return -EIO;`
	`26`	`+ tty_kref_get(tty);`
	`27`	`+ return mutex_lock_interruptible(&tty->legacy_mutex);`
	`28`	`+}`
	`29`	`+`
`22`	`30`	`void __lockfunc tty_unlock(struct tty_struct *tty)`
`23`	`31`	`{`
`24`	`32`	`if (WARN(tty->magic != TTY_MAGIC, "U Bad %p\n", tty))`