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SubjectRe: [RFC][PATCH 02/13] stop_machine: Fix stop_cpus_in_progress ordering
On Fri, 26 Jul 2019 16:54:11 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> Make sure the entire for loop has stop_cpus_in_progress set.


> kernel/stop_machine.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -383,6 +383,7 @@ static bool queue_stop_cpus_work(const s
> */
> preempt_disable();
> stop_cpus_in_progress = true;
> + barrier();

Like smp_mb() shouldn't barrier() have a comment to what is being
ordered and why?

-- Steve

> 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 s
> if (cpu_stop_queue_work(cpu, work))
> queued = true;
> }
> + barrier();
> stop_cpus_in_progress = false;
> preempt_enable();
>
>

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