linux-kernel - Subject: [PATCH] tty ldisc: Close/Reopen race prevention should check the proper flag

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Message-ID: <4FEFF3DF.9000909@liveu.tv>
Date:	Sun, 01 Jul 2012 09:53:19 +0300
From:	Shachar Shemesh <shachar@...eu.tv>
To:	unlisted-recipients:; (no To-header on input)
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Subject: [PATCH] tty ldisc: Close/Reopen race prevention should check
 the proper flag

From: Shachar Shemesh <shachar@...eu.tv>

Commit acfa747b introduced the TTY_HUPPING flag to distinguish closed 
TTY from currently closing ones. The test in tty_set_ldisc still 
remained pointing at the old flag. This causes pppd to sometimes lapse 
into uninterruptible sleep when killed and restarted.

Signed-off-by: Shachar Shemesh <shachar@...eu.tv>
---
Tested with 3.2.20 kernel.

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 24b95db..a662a24 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -658,7 +658,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
          goto enable;
      }

-    if (test_bit(TTY_HUPPED, &tty->flags)) {
+    if (test_bit(TTY_HUPPING, &tty->flags)) {
          /* We were raced by the hangup method. It will have stomped
             the ldisc data and closed the ldisc down */
          clear_bit(TTY_LDISC_CHANGING, &tty->flags);


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