linux-kernel - [RFC][PATCH 01/16] stop_machine: Fix stop_cpus_in

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Message-Id: <20190218173513.946214276@infradead.org>
Date:   Mon, 18 Feb 2019 17:56:21 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     mingo@...nel.org, tglx@...utronix.de, pjt@...gle.com,
        tim.c.chen@...ux.intel.com, torvalds@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: [RFC][PATCH 01/16] stop_machine: Fix stop_cpus_in_progress ordering

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(+)

--- 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();