linux-kernel - Re: [PATCH 3/3] cpuidle: Using the wake_up_all_idle

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Message-ID: <20140904154710.GH346@worktop.programming.kicks-ass.net>
Date:	Thu, 4 Sep 2014 17:47:10 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"luto@...capital.net" <luto@...capital.net>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Liu, Changcheng" <changcheng.liu@...el.com>,
	"Wang, Xiaoming" <xiaoming.wang@...el.com>,
	"Chakravarty, Souvik K" <souvik.k.chakravarty@...el.com>
Subject: Re: [PATCH 3/3] cpuidle: Using the wake_up_all_idle_cpus() to wake
 up all idle cpus

On Thu, Sep 04, 2014 at 01:39:38PM +0000, Liu, Chuansheng wrote:
> > So IIUC, kick_all_cpus_sync is a broken function, right ?

> kick_all_cpus_sync has other callers, and those other callers want the
> old behavior.  I think this should be a new function.

Correct, things like arch/powerpc/mm/pgtable_64.c:pmdp_clear_flush()
really want the old behaviour. It basically uses
local_irq_disable()/local_irq_enable() vs kick_all_cpus_sync() as a RCU
like serialization primitive.
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