linux-kernel - [RFC PATCH 2/6] stop_machine: don't do for_each_cpu() twice in queue_stop_cpus

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Message-ID: <20150626021512.GA5697@redhat.com>
Date:	Fri, 26 Jun 2015 04:15:12 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>, paulmck@...ux.vnet.ibm.com,
	tj@...nel.org, mingo@...hat.com, der.herr@...r.at,
	dave@...olabs.net, riel@...hat.com, viro@...IV.linux.org.uk,
	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/6] stop_machine: don't do for_each_cpu() twice in
	queue_stop_cpus_work()

queue_stop_cpus_work() can do everything in one for_each_cpu() loop.
This simplifies this code a bit, and this is also preparation for the
locking changes.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/stop_machine.c |   17 +++++++----------
 1 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 6e677b0..6212208 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -303,22 +303,19 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask,
 	struct cpu_stop_work *work;
 	unsigned int cpu;
 
-	/* initialize works and done */
-	for_each_cpu(cpu, cpumask) {
-		work = &per_cpu(cpu_stopper.stop_work, cpu);
-		work->fn = fn;
-		work->arg = arg;
-		work->done = done;
-	}
-
 	/*
 	 * Disable preemption while queueing to avoid getting
 	 * preempted by a stopper which might wait for other stoppers
 	 * to enter @fn which can lead to deadlock.
 	 */
 	lg_global_lock(&stop_cpus_lock);
-	for_each_cpu(cpu, cpumask)
-		cpu_stop_queue_work(cpu, &per_cpu(cpu_stopper.stop_work, cpu));
+	for_each_cpu(cpu, cpumask) {
+		work = &per_cpu(cpu_stopper.stop_work, cpu);
+		work->fn = fn;
+		work->arg = arg;
+		work->done = done;
+		cpu_stop_queue_work(cpu, work);
+	}
 	lg_global_unlock(&stop_cpus_lock);
 }
 
-- 
1.5.5.1

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