Try reinstating locks that affect cpu hotplug around sched affinity calls.

-ck

---
 kernel/sched/bfs.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-3.15.5-ck1/kernel/sched/bfs.c
===================================================================
--- linux-3.15.5-ck1.orig/kernel/sched/bfs.c	2014-07-18 11:21:26.343767043 +1000
+++ linux-3.15.5-ck1/kernel/sched/bfs.c	2014-07-23 23:22:35.445070612 +1000
@@ -4321,11 +4321,13 @@ long sched_setaffinity(pid_t pid, const
 	struct task_struct *p;
 	int retval;
 
+	get_online_cpus();
 	rcu_read_lock();
 
 	p = find_process_by_pid(pid);
 	if (!p) {
 		rcu_read_unlock();
+		put_online_cpus();
 		return -ESRCH;
 	}
 
@@ -4382,6 +4384,7 @@ out_free_cpus_allowed:
 	free_cpumask_var(cpus_allowed);
 out_put_task:
 	put_task_struct(p);
+	put_online_cpus();
 	return retval;
 }
 
@@ -4427,6 +4430,7 @@ long sched_getaffinity(pid_t pid, cpumas
 	unsigned long flags;
 	int retval;
 
+	get_online_cpus();
 	rcu_read_lock();
 
 	retval = -ESRCH;
@@ -4444,6 +4448,7 @@ long sched_getaffinity(pid_t pid, cpumas
 
 out_unlock:
 	rcu_read_unlock();
+	put_online_cpus();
 
 	return retval;
 }