Subject: [PATCH] tty ldisc: Close/Reopen race prevention should checkthe proper flag

From: Shachar Shemesh
Date: Sun Jul 01 2012 - 02:54:02 EST

From: Shachar Shemesh <shachar@xxxxxxxx>

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@xxxxxxxx>
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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