[RFC PATCH v4 01/19] stop_machine: Fix stop_cpus_in_progress ordering

[Vineeth Remanan Pillai]

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Make sure the entire for loop has stop_cpus_in_progress set.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/stop_machine.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index b4f83f7bdf86..c7031a22aa7b 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -383,6 +383,7 @@ static bool queue_stop_cpus_work(const struct cpumask *cpumask,
 	 */
 	preempt_disable();
 	stop_cpus_in_progress = true;
+	barrier();
 	for_each_cpu(cpu, cpumask) {
 		work = &per_cpu(cpu_stopper.stop_work, cpu);
 		work->fn = fn;
@@ -391,6 +392,7 @@ static bool queue_stop_cpus_work(const struct cpumask *cpumask,
 		if (cpu_stop_queue_work(cpu, work))
 			queued = true;
 	}
+	barrier();
 	stop_cpus_in_progress = false;
 	preempt_enable();
 
-- 
2.17.1