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 if we change
tsk->cpus_allowed. Otherwise RT scheduler may confuse.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4DD4B3FA.5060901@jp.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

5 files changed, 24 insertions, 12 deletions

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index f20eb8f16025..e9eaec522655 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -146,7 +146,7 @@ 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);
+        do_set_cpus_allowed(p, cpu_possible_mask);
         return cpumask_any(cpu_active_mask);
 }
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index dc8871295a5a..8da84b7bc1b8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1841,9 +1841,16 @@ static inline void rcu_copy_process(struct task_struct *p)
 #endif
 
 #ifdef CONFIG_SMP
+extern void do_set_cpus_allowed(struct task_struct *p,
+                               const struct cpumask *new_mask);
+
 extern int set_cpus_allowed_ptr(struct task_struct *p,
                                 const struct cpumask *new_mask);
 #else
+static inline void do_set_cpus_allowed(struct task_struct *p,
+                                      const struct cpumask *new_mask)
+{
+}
 static inline int set_cpus_allowed_ptr(struct task_struct *p,
                                        const struct cpumask *new_mask)
 {
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 1ceeb049c827..9c9b7545c810 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2190,7 +2190,7 @@ int cpuset_cpus_allowed_fallback(struct task_struct *tsk)
         rcu_read_lock();
         cs = task_cs(tsk);
         if (cs)
-                cpumask_copy(&tsk->cpus_allowed, cs->cpus_allowed);
+                do_set_cpus_allowed(tsk, cs->cpus_allowed);
         rcu_read_unlock();
 
         /*
@@ -2217,7 +2217,7 @@ int cpuset_cpus_allowed_fallback(struct task_struct *tsk)
                  * Like above we can temporary set any mask and rely on
                  * set_cpus_allowed_ptr() as synchronization point.
                  */
-                cpumask_copy(&tsk->cpus_allowed, cpu_possible_mask);
+                do_set_cpus_allowed(tsk, cpu_possible_mask);
                 cpu = cpumask_any(cpu_active_mask);
         }
 
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3b34d2732bce..4ba7cccb4994 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -202,8 +202,8 @@ void kthread_bind(struct task_struct *p, unsigned int cpu)
                 return;
         }
 
-        p->cpus_allowed = cpumask_of_cpu(cpu);
-        p->rt.nr_cpus_allowed = 1;
+        /* It's safe because the task is inactive. */
+        do_set_cpus_allowed(p, cpumask_of(cpu));
         p->flags |= PF_THREAD_BOUND;
 }
 EXPORT_SYMBOL(kthread_bind);
diff --git a/kernel/sched.c b/kernel/sched.c
index a80ee911900e..cbb3a0eee58e 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5860,7 +5860,7 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu)
         idle->state = TASK_RUNNING;
         idle->se.exec_start = sched_clock();
 
-        cpumask_copy(&idle->cpus_allowed, cpumask_of(cpu));
+        do_set_cpus_allowed(idle, cpumask_of(cpu));
         /*
          * We're having a chicken and egg problem, even though we are
          * holding rq->lock, the cpu isn't yet set to this cpu so the
@@ -5948,6 +5948,16 @@ static inline void sched_init_granularity(void)
 }
 
 #ifdef CONFIG_SMP
+void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
+{
+        if (p->sched_class && p->sched_class->set_cpus_allowed)
+                p->sched_class->set_cpus_allowed(p, new_mask);
+        else {
+                cpumask_copy(&p->cpus_allowed, new_mask);
+                p->rt.nr_cpus_allowed = cpumask_weight(new_mask);
+        }
+}
+
 /*
  * This is how migration works:
  *
@@ -5993,12 +6003,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
                 goto out;
         }
 
-        if (p->sched_class->set_cpus_allowed)
-                p->sched_class->set_cpus_allowed(p, new_mask);
-        else {
-                cpumask_copy(&p->cpus_allowed, new_mask);
-                p->rt.nr_cpus_allowed = cpumask_weight(new_mask);
-        }
+        do_set_cpus_allowed(p, new_mask);
 
         /* Can the task run on the task's current CPU? If so, we're done */
         if (cpumask_test_cpu(task_cpu(p), new_mask))