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From:   Vineeth Remanan Pillai <vpillai@digitalocean.com>
To:     Nishanth Aravamudan <naravamudan@digitalocean.com>,
        Julien Desfossez <jdesfossez@digitalocean.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tim Chen <tim.c.chen@linux.intel.com>, mingo@kernel.org,
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Cc:     linux-kernel@vger.kernel.org, subhra.mazumdar@oracle.com,
        fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com,
        Phil Auld <pauld@redhat.com>, Aaron Lu <aaron.lwe@gmail.com>,
        Aubrey Li <aubrey.intel@gmail.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: [RFC PATCH v2 01/17] stop_machine: Fix stop_cpus_in_progress ordering
Date:   Tue, 23 Apr 2019 16:18:06 +0000
Message-Id: <c40cb6dd8fb9fcaa26734f85cde40bb2a6688758.1556025155.git.vpillai@digitalocean.com>
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From: Peter Zijlstra (Intel) <peterz@infradead.org>

Make sure the entire for loop has stop_cpus_in_progress set.

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

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 067cb83f37ea..583119e0c51c 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -375,6 +375,7 @@ 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;
@@ -383,6 +384,7 @@ 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