linux-kernel - [tip:sched/core] sched: Fix the broken sched_rr_get

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Message-ID: <tip-a59f4e079d19464eebb9b06513a1d4f55fdae5ba@git.kernel.org>
Date:	Thu, 24 Jan 2013 12:15:35 -0800
From:	tip-bot for Zhu Yanhai <gaoyang.zyh@...bao.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, pjt@...gle.com,
	peterz@...radead.org, rostedt@...dmis.org,
	akpm@...ux-foundation.org, tglx@...utronix.de,
	gaoyang.zyh@...bao.com
Subject: [tip:sched/core] sched: Fix the broken sched_rr_get_interval()

Commit-ID:  a59f4e079d19464eebb9b06513a1d4f55fdae5ba
Gitweb:     http://git.kernel.org/tip/a59f4e079d19464eebb9b06513a1d4f55fdae5ba
Author:     Zhu Yanhai <gaoyang.zyh@...bao.com>
AuthorDate: Tue, 8 Jan 2013 12:56:52 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 24 Jan 2013 14:41:00 +0100

sched: Fix the broken sched_rr_get_interval()

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@...bao.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Paul Turner <pjt@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-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@...nel.org>
---
 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 5eea870..a7a19ff 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6101,7 +6101,7 @@ 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;
 }
--
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