This is a note to let you know that I've just added the patch titled
sched/fair: Do not announce throttled next buddy in dequeue_task_fair()
to the 4.4-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:
sched-fair-do-not-announce-throttled-next-buddy-in-dequeue_task_fair.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 754bd598be9bbc953bc709a9e8ed7f3188bfb9d7 Mon Sep 17 00:00:00 2001
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Date: Thu, 16 Jun 2016 15:57:15 +0300
Subject: sched/fair: Do not announce throttled next buddy in dequeue_task_fair()
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
commit 754bd598be9bbc953bc709a9e8ed7f3188bfb9d7 upstream.
Hierarchy could be already throttled at this point. Throttled next
buddy could trigger a NULL pointer dereference in pick_next_task_fair().
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/146608183552.21905.15924473394414832071.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Ben Pineau <benjamin.pineau@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4233,15 +4233,14 @@ static void dequeue_task_fair(struct rq
/* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight) {
+ /* Avoid re-evaluating load for this entity: */
+ se = parent_entity(se);
/*
* Bias pick_next to pick a task from this cfs_rq, as
* p is sleeping when it is within its sched_slice.
*/
- if (task_sleep && parent_entity(se))
- set_next_buddy(parent_entity(se));
-
- /* avoid re-evaluating load for this entity */
- se = parent_entity(se);
+ if (task_sleep && se && !throttled_hierarchy(cfs_rq))
+ set_next_buddy(se);
break;
}
flags |= DEQUEUE_SLEEP;
Patches currently in stable-queue which might be from khlebnikov@xxxxxxxxxxxxxx are
queue-4.4/sched-fair-do-not-announce-throttled-next-buddy-in-dequeue_task_fair.patch
queue-4.4/sched-fair-initialize-throttle_count-for-new-task-groups-lazily.patch