[RFC PATCH 13/15] sched: Protect nohz task cpu affinity

[Frederic Weisbecker]

Don't allow to change a nohz task cpu affinity as we want them
to be bound to a single CPU and we want this affinity not to
change.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxxxx>
Cc: Tim Pepper <lnxninja@xxxxxxxxxxxxxxxxxx>
---
 kernel/sched.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 4412493..bd0a41f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5712,6 +5712,13 @@ again:
 		goto out;
 	}
 
+	/* Nohz tasks must keep their affinity */
+	if (test_tsk_thread_flag(p, TIF_NOHZ) &&
+	    !cpumask_equal(&p->cpus_allowed, new_mask)) {
+		ret = -EBUSY;
+		goto out;
+	}
+
 	if (p->sched_class->set_cpus_allowed)
 		p->sched_class->set_cpus_allowed(p, new_mask);
 	else {
-- 
1.7.3.2

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