linux-kernel - [patch] sched, rt: fix migrate

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Date:	Tue, 23 Aug 2011 16:12:43 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: [patch] sched, rt: fix migrate_enable() thinko


Assigning mask = tsk_cpus_allowed(p) after p->migrate_disable = 0 ensures
that we won't see a mask change.. no push/pull, we stack tasks on one CPU.

Also add a couple fields to sched_debug for the next guy.

Signed-off-by: Mike Galbraith <efault@....de>

---
 kernel/sched.c       |    4 +++-
 kernel/sched_debug.c |    3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -6375,12 +6375,14 @@ void migrate_enable(void)
 	 */
 	rq = this_rq();
 	raw_spin_lock_irqsave(&rq->lock, flags);
-	p->migrate_disable = 0;
 	mask = tsk_cpus_allowed(p);
+	p->migrate_disable = 0;
 
 	WARN_ON(!cpumask_test_cpu(smp_processor_id(), mask));
 
 	if (!cpumask_equal(&p->cpus_allowed, mask)) {
+		/* Get the mask now that migration is enabled */
+		mask = tsk_cpus_allowed(p);
 		if (p->sched_class->set_cpus_allowed)
 			p->sched_class->set_cpus_allowed(p, mask);
 		p->rt.nr_cpus_allowed = cpumask_weight(mask);
Index: linux-2.6/kernel/sched_debug.c
===================================================================
--- linux-2.6.orig/kernel/sched_debug.c
+++ linux-2.6/kernel/sched_debug.c
@@ -235,6 +235,7 @@ void print_rt_rq(struct seq_file *m, int
 	P(rt_throttled);
 	PN(rt_time);
 	PN(rt_runtime);
+	P(rt_nr_migratory);
 
 #undef PN
 #undef P
@@ -484,6 +485,8 @@ void proc_sched_show_task(struct task_st
 	P(se.load.weight);
 	P(policy);
 	P(prio);
+	P(migrate_disable);
+	P(rt.nr_cpus_allowed);
 #undef PN
 #undef __PN
 #undef P


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