linux-kernel - [tip:sched/core] stop_machine: Don't do for_each_cpu() twice in queue_stop_cpus

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Date:	Mon, 3 Aug 2015 10:09:02 -0700
From:	tip-bot for Oleg Nesterov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	efault@....de, linux-kernel@...r.kernel.org, hpa@...or.com,
	peterz@...radead.org, tj@...nel.org, tglx@...utronix.de,
	mingo@...nel.org, oleg@...hat.com, torvalds@...ux-foundation.org
Subject: [tip:sched/core] stop_machine: Don't do for_each_cpu()
  twice in queue_stop_cpus_work()

Commit-ID:  b377c2a089d4538e6e62e51fa595c896c314d83d
Gitweb:     http://git.kernel.org/tip/b377c2a089d4538e6e62e51fa595c896c314d83d
Author:     Oleg Nesterov <oleg@...hat.com>
AuthorDate: Tue, 30 Jun 2015 03:29:48 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 3 Aug 2015 12:21:26 +0200

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.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: dave@...olabs.net
Cc: der.herr@...r.at
Cc: paulmck@...ux.vnet.ibm.com
Cc: riel@...hat.com
Cc: viro@...IV.linux.org.uk
Link: http://lkml.kernel.org/r/20150630012948.GA23927@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/stop_machine.c | 17 +++++++----------
 1 file 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);
 }
 
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