linux-kernel - [ 01/48] audit: wait_for_auditd() should use TASK

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Date:	Tue, 18 Jun 2013 09:17:27 -0700
From:	Greg Kroah-Hartman <greg@...ah.com>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Guy Streeter <streeter@...hat.com>,
	Eric Paris <eparis@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 01/48] audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@...hat.com>

commit f000cfdde5de4fc15dead5ccf524359c07eadf2b upstream.

audit_log_start() does wait_for_auditd() in a loop until
audit_backlog_wait_time passes or audit_skb_queue has a room.

If signal_pending() is true this becomes a busy-wait loop, schedule() in
TASK_INTERRUPTIBLE won't block.

Thanks to Guy for fully investigating and explaining the problem.

(akpm: that'll cause the system to lock up on a non-preemptible
uniprocessor kernel)

(Guy: "Our customer was in fact running a uniprocessor machine, and they
reported a system hang.")

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reported-by: Guy Streeter <streeter@...hat.com>
Cc: Eric Paris <eparis@...hat.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/audit.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1107,7 +1107,7 @@ static inline void audit_get_stamp(struc
 static void wait_for_auditd(unsigned long sleep_time)
 {
 	DECLARE_WAITQUEUE(wait, current);
-	set_current_state(TASK_INTERRUPTIBLE);
+	set_current_state(TASK_UNINTERRUPTIBLE);
 	add_wait_queue(&audit_backlog_wait, &wait);
 
 	if (audit_backlog_limit &&


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