[ 3.5.y.z extended stable ] Patch "sched: Fix the broken sched_rr_get_interval()" has been added to staging queue

[Luis Henriques]

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

    sched: Fix the broken sched_rr_get_interval()

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.
-Luis

------

>From 8e01d996e0b9ad069f588c92f055875e69068f20 Mon Sep 17 00:00:00 2001
From: Zhu Yanhai <gaoyang.zyh at taobao.com>
Date: Tue, 8 Jan 2013 12:56:52 +0800
Subject: [PATCH] sched: Fix the broken sched_rr_get_interval()

commit a59f4e079d19464eebb9b06513a1d4f55fdae5ba upstream.

The caller of sched_sliced() should pass se.cfs_rq and se as the
arguments, however in sched_rr_get_interval() we gave it
rq.cfs_rq and se, which made the following computation obviously
wrong.

The change was introduced by commit:

  77034937dc45 sched: fix crash in sys_sched_rr_get_interval()

... 5 years ago, while it had been the correct 'cfs_rq_of' before
the commit. The change seems to be irrelevant to the commit
msg, which was to return a 0 timeslice for tasks that are on an
idle runqueue. So I believe that was just a plain typo.

Signed-off-by: Zhu Yanhai <gaoyang.zyh at taobao.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Paul Turner <pjt at google.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Steven Rostedt <rostedt at goodmis.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Link: http://lkml.kernel.org/r/1357621012-15039-1-git-send-email-gaoyang.zyh@taobao.com
[ Since this is an ABI and an old bug, we'll test this via a
  slow upstream route, to hopefully discover any app breakage. ]
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Cc: Li Zefan <lizefan at huawei.com>
Acked-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c099cc6..eb12b9e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5250,7 +5250,7 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task
 	 * idle runqueue:
 	 */
 	if (rq->cfs.load.weight)
-		rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
+		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));

 	return rr_interval;
 }
--
1.8.3.2