linux-kernel - Re: [PATCH 0/3] cpuidle: updates related to tick_broadcast

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Message-ID: <5550C721.2050906@arm.com>
Date:	Mon, 11 May 2015 16:13:37 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	"peterz@...radead.org" <peterz@...radead.org>
CC:	Sudeep Holla <sudeep.holla@....com>,
	"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 0/3] cpuidle: updates related to tick_broadcast_enter()
 failures



On 10/05/15 00:15, Rafael J. Wysocki wrote:
> On Saturday, May 09, 2015 10:33:05 PM Rafael J. Wysocki wrote:
>> On Saturday, May 09, 2015 10:11:41 PM Rafael J. Wysocki wrote:
>>> On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote:
>>>> Hi Rafael,
>>>>
>>>> On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote:
>>>
>>> [cut]
>>>
>>>>>>
>>>>>> +	/* Take note of the planned idle state. */
>>>>>> +	idle_set_state(smp_processor_id(), target_state);
>>>>>
>>>>> And I wouldn't do this either.
>>>>>
>>>>> The behavior here is pretty much as though the driver demoted the state chosen
>>>>> by the governor and we don't call idle_set_state() again in those cases.
>>>>
>>>> Why is this wrong?
>>>
>>> It is not "wrong", but incomplete, because demotions done by the cpuidle driver
>>> should also be taken into account in the same way.
>>>
>>> But I'm seeing that the recent patch of mine that made cpuidle_enter_state()
>>> call default_idle_call() was a mistake, because it might confuse find_idlest_cpu()
>>> significantly as to what state the CPU is in.  I'll drop that one for now.
>>
>> OK, done.
>>
>> So after I've dropped it I think we need to do three things:
>> (1) Move the idle_set_state() calls to cpuidle_enter_state().
>> (2) Make cpuidle_enter_state() call default_idle_call() again, but this time
>>      do that *before* it has called idle_set_state() for target_state.
>> (3) Introduce demotion as per my last patch.
>>
>> Let me cut patches for that.
>
> Done as per the above and the patches follow in replies to this messge.
>
> All on top of the current linux-next branch of the linux-pm.git tree.
>

Tested on ARM Vexpress platforms with one of the CPU in broadcast mode
and also with broadcast timer. So, you can add:

Tested-by: Sudeep Holla <sudeep.holla@....com>

Regards,
Sudeep
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