[RFC PATCH for 4.16 01/11] Fix: membarrier: add missing preempt off around smp_call_function_many

smp_call_function_many requires disabling preemption around the call.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
CC: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
CC: Peter Zijlstra <redacted>
CC: Paul E. McKenney <redacted>
CC: Boqun Feng <redacted>
CC: Andrew Hunter <redacted>
CC: Maged Michael <redacted>
CC: Avi Kivity <avi-VrcmuVmyx1hWk0Htik3J/w@public.gmane.org>
CC: Benjamin Herrenschmidt <redacted>
CC: Paul Mackerras <redacted>
CC: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
CC: Dave Watson <redacted>
CC: Thomas Gleixner <redacted>
CC: Ingo Molnar <redacted>
CC: "H. Peter Anvin" <redacted>
CC: Andrea Parri <redacted>
CC: <redacted> #v4.14
---
 kernel/sched/membarrier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index dd7908743dab..9bcbacba82a8 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c

@@ -89,7 +89,9 @@ static int membarrier_private_expedited(void)
 		rcu_read_unlock();
 	}
 	if (!fallback) {
+		preempt_disable();
 		smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
+		preempt_enable();
 		free_cpumask_var(tmpmask);
 	}
 	cpus_read_unlock();

-- 
2.11.0