linux-kernel - [tip:sched/urgent] sched: Revert 738d2be, simplify set_task

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Date:	Wed, 23 Dec 2009 09:06:36 GMT
From:	tip-bot for Peter Zijlstra <peterz@...radead.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, eparis@...hat.com, peterz@...radead.org,
	tglx@...utronix.de, mingo@...e.hu
Subject: [tip:sched/urgent] sched: Revert 738d2be, simplify set_task_cpu()

Commit-ID:  0c69774e6ce94364cfaa8bdeb18061edc414bc5a
Gitweb:     http://git.kernel.org/tip/0c69774e6ce94364cfaa8bdeb18061edc414bc5a
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Tue, 22 Dec 2009 15:43:19 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 23 Dec 2009 10:04:10 +0100

sched: Revert 738d2be, simplify set_task_cpu()

Effectively reverts 738d2be4301007f054541c5c4bf7fb6a361c9b3a.

As demonstrated by Eric, we really need to call __set_task_cpu()
early in the fork() path to properly initialize the various task
state -- specifically the cgroup state through set_task_rq().

[ we could probably fix this by explicitly calling
  __set_task_cpu() from   sched_fork(), but lets try that for the
  next cycle and simply revert to the old behaviour for now. ]

Reported-by: Eric Paris <eparis@...hat.com>
Tested-by: Eric Paris <eparis@...hat.com>,
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: efault@....de
LKML-Reference: <1261492999.4937.36.camel@...top>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched.c |    9 ++++-----
 1 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 87f1f47..c535cc4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2045,11 +2045,10 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 
 	trace_sched_migrate_task(p, new_cpu);
 
-	if (task_cpu(p) == new_cpu)
-		return;
-
-	p->se.nr_migrations++;
-	perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 1, NULL, 0);
+	if (task_cpu(p) != new_cpu) {
+		p->se.nr_migrations++;
+		perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 1, NULL, 0);
+	}
 
 	__set_task_cpu(p, new_cpu);
 }
--
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