linux-kernel - Re: 9908859acaa9 cpuidle/menu: add per CPU PM QoS resume latency consideration

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Message-ID: <6f016a9b-8968-e7c1-b1c7-c6b023431623@linaro.org>
Date:   Thu, 23 Feb 2017 21:58:47 +0800
From:   Alex Shi <alex.shi@...aro.org>
To:     Mike Galbraith <efault@....de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Rik van Riel <riel@...hat.com>
Subject: Re: 9908859acaa9 cpuidle/menu: add per CPU PM QoS resume latency
 consideration



On 02/23/2017 09:08 PM, Mike Galbraith wrote:
> On Thu, 2017-02-23 at 13:15 +0100, Rafael J. Wysocki wrote:
>> On Wednesday, February 22, 2017 10:55:04 PM Alex Shi wrote:
>>>>
>>>> Its not hard; spinlock_t ends up being a mutex, and this is ran
>>>> from the
>>>> idle thread. What thread do you think we ought to run when we
>>>> block
>>>> idle?
>>>>
>>>
>>> Straight right.
>>> Thanks for explanations! :)
>>
>> I overlooked that, sorry.
>>
>> Shall we revert?
>>
>> I don't want RT to be broken because of this.
> 
> Just whacking the lock would take care of that.  The question is who is
> gonna use this, and what does it really buy them?  When I look at that
> commit, an eyebrow raises, lock or no lock.
> 

Right per cpu lock for per cpu data is unnecessary.