[ 3.5.y.z extended stable ] Patch "workqueue: exit rescuer_thread() as TASK_RUNNING" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    workqueue: exit rescuer_thread() as TASK_RUNNING

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 98f8af8753cd3da6cc5b680079d64ad774989e4c Mon Sep 17 00:00:00 2001
From: Mike Galbraith <mgalbraith at suse.de>
Date: Wed, 28 Nov 2012 07:17:18 +0100
Subject: [PATCH] workqueue: exit rescuer_thread() as TASK_RUNNING

commit 412d32e6c98527078779e5b515823b2810e40324 upstream.

A rescue thread exiting TASK_INTERRUPTIBLE can lead to a task scheduling
off, never to be seen again.  In the case where this occurred, an exiting
thread hit reiserfs homebrew conditional resched while holding a mutex,
bringing the box to its knees.

PID: 18105  TASK: ffff8807fd412180  CPU: 5   COMMAND: "kdmflush"
 #0 [ffff8808157e7670] schedule at ffffffff8143f489
 #1 [ffff8808157e77b8] reiserfs_get_block at ffffffffa038ab2d [reiserfs]
 #2 [ffff8808157e79a8] __block_write_begin at ffffffff8117fb14
 #3 [ffff8808157e7a98] reiserfs_write_begin at ffffffffa0388695 [reiserfs]
 #4 [ffff8808157e7ad8] generic_perform_write at ffffffff810ee9e2
 #5 [ffff8808157e7b58] generic_file_buffered_write at ffffffff810eeb41
 #6 [ffff8808157e7ba8] __generic_file_aio_write at ffffffff810f1a3a
 #7 [ffff8808157e7c58] generic_file_aio_write at ffffffff810f1c88
 #8 [ffff8808157e7cc8] do_sync_write at ffffffff8114f850
 #9 [ffff8808157e7dd8] do_acct_process at ffffffff810a268f
    [exception RIP: kernel_thread_helper]
    RIP: ffffffff8144a5c0  RSP: ffff8808157e7f58  RFLAGS: 00000202
    RAX: 0000000000000000  RBX: 0000000000000000  RCX: 0000000000000000
    RDX: 0000000000000000  RSI: ffffffff8107af60  RDI: ffff8803ee491d18
    RBP: 0000000000000000   R8: 0000000000000000   R9: 0000000000000000
    R10: 0000000000000000  R11: 0000000000000000  R12: 0000000000000000
    R13: 0000000000000000  R14: 0000000000000000  R15: 0000000000000000
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018

Signed-off-by: Mike Galbraith <mgalbraith at suse.de>
Signed-off-by: Tejun Heo <tj at kernel.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 kernel/workqueue.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 478f2ab..a6a4c90 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2045,8 +2045,10 @@ static int rescuer_thread(void *__wq)
 repeat:
 	set_current_state(TASK_INTERRUPTIBLE);

-	if (kthread_should_stop())
+	if (kthread_should_stop()) {
+		__set_current_state(TASK_RUNNING);
 		return 0;
+	}

 	/*
 	 * See whether any cpu is asking for help.  Unbounded
--
1.7.9.5