[RFC][PATCH 01/16] stop_machine: Fix stop_cpus_in_progress ordering

[Peter Zijlstra]

Make sure the entire for loop has stop_cpus_in_progress set.

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

--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -375,6 +375,7 @@ static bool queue_stop_cpus_work(const s
         */
        preempt_disable();
        stop_cpus_in_progress = true;
+       barrier();
        for_each_cpu(cpu, cpumask) {
                work = &per_cpu(cpu_stopper.stop_work, cpu);
                work->fn = fn;
@@ -383,6 +384,7 @@ static bool queue_stop_cpus_work(const s
                if (cpu_stop_queue_work(cpu, work))
                        queued = true;
        }
+       barrier();
        stop_cpus_in_progress = false;
        preempt_enable();