[PATCH] Fix: membarrier: add missing preempt off around smp_call_function_many

[Mathieu Desnoyers]

smp_call_function_many requires disabling preemption around the call.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Peter Zijlstra <pet...@infradead.org>
CC: Paul E. McKenney <paul...@linux.vnet.ibm.com>
CC: Boqun Feng <boqun.f...@gmail.com>
CC: Andrew Hunter <a...@google.com>
CC: Maged Michael <maged.mich...@gmail.com>
CC: Avi Kivity <a...@scylladb.com>
CC: Benjamin Herrenschmidt <b...@kernel.crashing.org>
CC: Paul Mackerras <pau...@samba.org>
CC: Michael Ellerman <m...@ellerman.id.au>
CC: Dave Watson <davejwat...@fb.com>
CC: Thomas Gleixner <t...@linutronix.de>
CC: Ingo Molnar <mi...@redhat.com>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Andrea Parri <parri.and...@gmail.com>
CC: <sta...@vger.kernel.org>    # 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