linux-kernel - Re: [Regression] kdesu broken

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Date:	Sat, 25 Jul 2009 13:07:03 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Ray Lee <ray-lk@...rabbit.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Regression] kdesu broken

> > See the thread starting here: ("possible regression with pty.c commit")
> >    http://lkml.org/lkml/2009/7/11/125
> 
> I am also facing a similar problem.
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=13815

Probably something like this fixes it. I'll be working on that Monday/Tuesday
along with various other bugs that need a review.

--


pty: ensure writes hit the reader before close

From: Alan Cox <alan@...ux.intel.com>

Logically we move the buffering from one side to the other
---

 drivers/char/pty.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)


diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 6e6942c..7555890 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -36,6 +36,15 @@ static struct tty_driver *ptm_driver;
 static struct tty_driver *pts_driver;
 #endif
 
+static int pty_empty(struct tty_struct *tty)
+{
+	if (tty->buf.memory_used == 0)
+		return 1;
+	if (test_bit(TTY_HUPPED, &tty->flags))
+		return 1;
+	return 0;
+}
+
 static void pty_close(struct tty_struct *tty, struct file *filp)
 {
 	BUG_ON(!tty);
@@ -47,9 +56,11 @@ 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;
 	if (!tty->link)
 		return;
+	wait_event_interruptible(tty->write_wait, pty_empty(tty->link));
 	tty->link->packet = 0;
 	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 	wake_up_interruptible(&tty->link->read_wait);
--
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