linux-kernel - Re: [PATCH V3 3/7] workqueue: Add helpers to schedule work on any cpu

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Date:	Tue, 19 Mar 2013 10:45:33 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	pjt@...gle.com, paul.mckenney@...aro.org, tglx@...utronix.de,
	tj@...nel.org, suresh.b.siddha@...el.com, venki@...gle.com,
	mingo@...hat.com, peterz@...radead.org, rostedt@...dmis.org
Cc:	linaro-kernel@...ts.linaro.org, robin.randhawa@....com,
	Steve.Bannister@....com, Liviu.Dudau@....com,
	charles.garcia-tobin@....com, Arvind.Chauhan@....com,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH V3 3/7] workqueue: Add helpers to schedule work on any cpu

On 18 March 2013 20:53, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> queue_work() queues work on current cpu. This may wake up an idle CPU, which is
> actually not required.
>
> Some of these works can be processed by any CPU and so we must select a non-idle
> CPU here. The initial idea was to modify implementation of queue_work(), but
> that may end up breaking lots of kernel code that would be a nightmare to debug.
>
> So, we finalized to adding new workqueue interfaces, for works that don't depend
> on a cpu to execute them.

Fixup:

commit 6e5b6fac3353f5e4e5490931b3eb6d3fd7864ca0
Author: Viresh Kumar <viresh.kumar@...aro.org>
Date:   Tue Mar 19 10:34:20 2013 +0530

    fixup! workqueue: Add helpers to schedule work on any cpu
---
 kernel/workqueue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index cf9c570..68daf50 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1242,7 +1242,7 @@ retry:
        if (!(wq->flags & WQ_UNBOUND)) {
                if (cpu == WORK_CPU_UNBOUND) {
                        if (on_any_cpu)
-                               cpu = sched_select_cpu(0);
+                               cpu = sched_select_non_idle_cpu(0);
                        else
                                cpu = raw_smp_processor_id();
                }
--
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