linux-kernel - [RFC PATCH] cpuset: fix cpuset_cpus_allowed_fallback() don't update tsk->rt.nr_cpus

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Message-Id: <20110428232228.3D57.A69D9226@jp.fujitsu.com>
Date:	Thu, 28 Apr 2011 23:20:50 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Li Zefan <lizf@...fujitsu.com>,
	Miao Xie <miaox@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com
Subject: [RFC PATCH] cpuset: fix cpuset_cpus_allowed_fallback() don't update tsk->rt.nr_cpus_allowed

Oleg, Peter,

I apologize if I misunderstand a code. I'm afraid we need following
patch. Is there any gurantte that cpusets user task is not RT task?



>From 400e24f7b6e15d1397dc82d74fdd1e0a631493ef Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Date: Thu, 28 Apr 2011 16:14:16 +0900
Subject: [PATCH] cpuset: fix cpuset_cpus_allowed_fallback() don't update tsk->rt.nr_cpus_allowed

The rule is, we have to update tsk->rt.nr_cpus_allowed too if we change
tsk->cpus_allowed.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Ingo Molnar <mingo@...e.hu>
---
 include/linux/cpuset.h |    1 +
 kernel/cpuset.c        |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index f20eb8f..42dcbdc 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -147,6 +147,7 @@ static inline void cpuset_cpus_allowed(struct task_struct *p,
 static inline int cpuset_cpus_allowed_fallback(struct task_struct *p)
 {
 	cpumask_copy(&p->cpus_allowed, cpu_possible_mask);
+	p->rt.nr_cpus_allowed = cpumask_weight(&p->cpus_allowed);
 	return cpumask_any(cpu_active_mask);
 }
 
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 1ceeb04..6e5bbe8 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2220,6 +2220,7 @@ int cpuset_cpus_allowed_fallback(struct task_struct *tsk)
 		cpumask_copy(&tsk->cpus_allowed, cpu_possible_mask);
 		cpu = cpumask_any(cpu_active_mask);
 	}
+	tsk->rt.nr_cpus_allowed = cpumask_weight(&tsk->cpus_allowed);
 
 	return cpu;
 }
-- 
1.7.3.1



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