Subject: sched, rt: Fix migrate_enable() thinko
From: Mike Galbraith <efault@gmx.de>
Date: Tue, 23 Aug 2011 16:12:43 +0200

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.

[ Build fix from Stratos Psomadakis <psomas@gentoo.org> ]

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1314108763.6689.4.camel@marge.simson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 kernel/sched/core.c  |    4 +++-
 kernel/sched/debug.c |    7 +++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

Index: linux-stable/kernel/sched/core.c
===================================================================
--- linux-stable.orig/kernel/sched/core.c
+++ linux-stable/kernel/sched/core.c
@@ -5355,12 +5355,14 @@ 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->nr_cpus_allowed = cpumask_weight(mask);
Index: linux-stable/kernel/sched/debug.c
===================================================================
--- linux-stable.orig/kernel/sched/debug.c
+++ linux-stable/kernel/sched/debug.c
@@ -237,6 +237,9 @@ void print_rt_rq(struct seq_file *m, int
 	P(rt_throttled);
 	PN(rt_time);
 	PN(rt_runtime);
+#ifdef CONFIG_SMP
+	P(rt_nr_migratory);
+#endif
 
 #undef PN
 #undef P
@@ -491,6 +494,10 @@ void proc_sched_show_task(struct task_st
 	P(se.load.weight);
 	P(policy);
 	P(prio);
+#ifdef CONFIG_PREEMPT_RT_FULL
+	P(migrate_disable);
+#endif
+	P(nr_cpus_allowed);
 #undef PN
 #undef __PN
 #undef P