linux-kernel - Re: [PATCH] cpuidle: Handle tick_broadcast

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Message-ID: <554BA5A8.3040009@linux.vnet.ibm.com>
Date:	Thu, 07 May 2015 23:19:28 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Sudeep Holla <sudeep.holla@....com>
CC:	"peterz@...radead.org" <peterz@...radead.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"rlippert@...gle.com" <rlippert@...gle.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] cpuidle: Handle tick_broadcast_enter() failure gracefully

On 05/07/2015 03:26 PM, Sudeep Holla wrote:
> Hi Preeti,
> 
> On 07/05/15 06:26, Preeti U Murthy wrote:
>> When a CPU has to enter an idle state where tick stops, it makes a call
>> to tick_broadcast_enter(). The call will fail if this CPU is the
>> broadcast CPU. Today, under such a circumstance, the arch cpuidle code
>> handles this CPU.  This is not convincing because not only are we not
>> aware what the arch cpuidle code does, but we also do not account for
>> the idle state residency time and usage of such a CPU.
>>
>> This scenario can be handled better by simply asking the cpuidle
>> governor to choose an idle state where in ticks do not stop. To
>> accommodate this change move the setting of runqueue idle state from the
>> core to the cpuidle driver, else the rq->idle_state will be set wrong.
>>
>> Signed-off-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
>> ---
>> Based on linux-pm/bleeding-edge
> 
> I am unable to apply this patch cleanly on linux-pm/bleeding-edge
> I think it conflicts with few patches that Rafael posted recently
> which are in the branch now.

Thanks so much for pointing out this! I have resent the patch as V2
after the rebase on the updated linux-pm/bleeding-edge branch

Regards
Preeti U Murthy
> 
> Regards,
> Sudeep
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