linux-kernel - [RFC PATCH v4 01/19] stop_machine: Fix stop_cpus_in

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Message-Id: <94254706c6b697b6351d604642c404ace101d3fb.1572437285.git.vpillai@digitalocean.com>
Date:   Wed, 30 Oct 2019 18:33:14 +0000
From:   Vineeth Remanan Pillai <vpillai@...italocean.com>
To:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Dario Faggioli <dfaggioli@...e.com>,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [RFC PATCH v4 01/19] stop_machine: Fix stop_cpus_in_progress ordering

From: Peter Zijlstra <peterz@...radead.org>

Make sure the entire for loop has stop_cpus_in_progress set.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 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