Patch "hung_task: fix false positive during vfork" has been added to the 3.1-stable tree

This is a note to let you know that I've just added the patch titled

hung_task: fix false positive during vfork

to the 3.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hung_task-fix-false-positive-during-vfork.patch
and it can be found in the queue-3.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mandeep Singh Baines <[email protected]>
Date: Tue, 3 Jan 2012 14:41:13 -0800
Subject: hung_task: fix false positive during vfork

From: Mandeep Singh Baines <[email protected]>

commit f9fab10bbd768b0e5254e53a4a8477a94bfc4b96 upstream.

vfork parent uninterruptibly and unkillably waits for its child to exec/exit. This wait is of unbounded length. Ignore such waits in the hung_task detector.

LKML-Reference: <1325344394.28904.43.camel@lappy>

---
 kernel/hung_task.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

@@ -74,11 +74,17 @@ static void check_hung_task(struct task_
 
 	/*
 	 * Ensure the task is not frozen.
-	 * Also, when a freshly created task is scheduled once, changes
-	 * its state to TASK_UNINTERRUPTIBLE without having ever been
-	 * switched out once, it musn't be checked.
+	 * Also, skip vfork and any other user process that freezer should skip.
 	 */
-	if (unlikely(t->flags & PF_FROZEN || !switch_count))
+	if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP)))
+	    return;
+
+	/*
+	 * When a freshly created task is scheduled once, changes its state to
+	 * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
+	 * musn't be checked.
+	 */
+	if (unlikely(!switch_count))
 		return;
 
 	if (switch_count != t->last_switch_count) {

Patches currently in stable-queue which might be from [email protected] are

queue-3.1/hung_task-fix-false-positive-during-vfork.patch queue-3.1/cgroups-fix-a-css_set-not-found-bug-in-cgroup_attach_proc.patch