linux-kernel - Re: inconsistent lock state (tty? input?)

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Date:	Mon, 13 Oct 2008 14:57:12 -0400
From:	Arjan van de Ven <arjan@...radead.org>
To:	Marcin Slusarz <marcin.slusarz@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Alan Cox <alan@...hat.com>,
	Dmitry Torokhov <dtor@...l.ru>
Subject: Re: inconsistent lock state (tty? input?)

On Mon, 13 Oct 2008 20:37:43 +0200
Marcin Slusarz <marcin.slusarz@...il.com> wrote:

> On current git (a447c0932445f92ce6f4c1bd020f62c5097a7842):
\

good spotting;

the patch below should fix this:

>From 26c117549415c55585f46ad38cd58a5f84f5adc7 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@...ux.intel.com>
Date: Mon, 13 Oct 2008 14:56:39 -0400
Subject: [PATCH] tty: make sure that proc_clear_tty stores the cpu flags

proc_clear_tty() gets called with interrupts off (while holding the task list lock)
from sys_setid. This means that it needs the _irqsave version of the locking primitives.

Reported-by: Marcin Slusarz <marcin.slusarz@...il.com>
Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
---
 drivers/char/tty_io.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index e4dce87..4715961 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -3595,9 +3595,10 @@ EXPORT_SYMBOL(tty_devnum);
 
 void proc_clear_tty(struct task_struct *p)
 {
-	spin_lock_irq(&p->sighand->siglock);
+	unsigned long flags;
+	spin_lock_irqsave(&p->sighand->siglock, flags);
 	p->signal->tty = NULL;
-	spin_unlock_irq(&p->sighand->siglock);
+	spin_unlock_irqrestore(&p->sighand->siglock, flags);
 }
 
 /* Called under the sighand lock */
-- 
1.5.5.1



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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