linux-kernel - [PATCH 07/12] tty: Wait interruptibly for tty lock on reopen

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Message-Id: <1448677557-16420-8-git-send-email-peter@hurleysoftware.com>
Date:	Fri, 27 Nov 2015 21:25:52 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org,
	Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH 07/12] 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@...leysoftware.com>
---
 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 64978ca..afd378e 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2064,7 +2064,12 @@ 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);
@@ -2151,6 +2156,7 @@ 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 79dac6f..75351e4 100644
--- a/drivers/tty/tty_mutex.c
+++ b/drivers/tty/tty_mutex.c
@@ -19,6 +19,14 @@ void 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 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 c3ea90a..c7c5d3c 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -645,6 +645,7 @@ extern long vt_compat_ioctl(struct tty_struct *tty,
 /* tty_mutex.c */
 /* functions for preparation of BKL removal */
 extern void tty_lock(struct tty_struct *tty);
+extern int  tty_lock_interruptible(struct tty_struct *tty);
 extern void tty_unlock(struct tty_struct *tty);
 extern void tty_lock_slave(struct tty_struct *tty);
 extern void tty_unlock_slave(struct tty_struct *tty);
-- 
2.6.3

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