linux-kernel - [PATCH 5/8] stop_machine: change __stop_cpus() to rely on cpu_stop_queue

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Message-ID: <20151115193323.GA8262@redhat.com>
Date:	Sun, 15 Nov 2015 20:33:23 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Milos Vyletel <milos@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>, Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 5/8] stop_machine: change __stop_cpus() to rely on
	cpu_stop_queue_work()

Change queue_stop_cpus_work() to return true if it queues at least one
work, this means that the caller should wait.

__stop_cpus() can check the value returned by queue_stop_cpus_work() and
avoid done.executed, just like stop_one_cpu() does.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/stop_machine.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 68b73c4..ed2019a 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -318,12 +318,13 @@ bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
 /* static data for stop_cpus */
 static DEFINE_MUTEX(stop_cpus_mutex);
 
-static void queue_stop_cpus_work(const struct cpumask *cpumask,
+static bool queue_stop_cpus_work(const struct cpumask *cpumask,
 				 cpu_stop_fn_t fn, void *arg,
 				 struct cpu_stop_done *done)
 {
 	struct cpu_stop_work *work;
 	unsigned int cpu;
+	bool queued = false;
 
 	/*
 	 * Disable preemption while queueing to avoid getting
@@ -336,9 +337,12 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask,
 		work->fn = fn;
 		work->arg = arg;
 		work->done = done;
-		cpu_stop_queue_work(cpu, work);
+		if (cpu_stop_queue_work(cpu, work))
+			queued = true;
 	}
 	lg_global_unlock(&stop_cpus_lock);
+
+	return queued;
 }
 
 static int __stop_cpus(const struct cpumask *cpumask,
@@ -347,9 +351,11 @@ static int __stop_cpus(const struct cpumask *cpumask,
 	struct cpu_stop_done done;
 
 	cpu_stop_init_done(&done, cpumask_weight(cpumask));
-	queue_stop_cpus_work(cpumask, fn, arg, &done);
+	if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
+		return -ENOENT;
 	wait_for_completion(&done.completion);
-	return done.executed ? done.ret : -ENOENT;
+	WARN_ON(!done.executed);
+	return done.ret;
 }
 
 /**
-- 
1.5.5.1

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