patch "tty: Wait interruptibly for tty lock on reopen" added to tty-testing

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    tty: Wait interruptibly for tty lock on reopen

to my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the tty-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


>From 0bfd464d3fdd5bb322f9cace4cc47f1796545cf7 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Sat, 9 Jan 2016 21:13:44 -0800
Subject: tty: Wait interruptibly for tty lock on reopen

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 <peter@hurleysoftware.com>
Cc: stable <stable@vger.kernel.org> # 4.4
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/tty_io.c    | 8 +++++++-
 drivers/tty/tty_mutex.c | 8 ++++++++
 include/linux/tty.h     | 1 +
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 892c92354745..765935b144d6 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2065,7 +2065,12 @@ retry_open:
 
 		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 @@ retry_open:
 	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
index 77703a391207..d2f3c4cd697f 100644
--- 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
index 2fd8708ea888..d9fb4b043f56 100644
--- 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);
-- 
2.7.0