linux-kernel - Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle implementations

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Date:	Wed, 20 Nov 2013 09:23:52 -0800
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Peter Zijlstra <peterz@...radead.org>, lenb@...nel.org,
	rjw@...ysocki.net, Eliezer Tamir <eliezer.tamir@...ux.intel.com>,
	Chris Leech <christopher.leech@...el.com>,
	David Miller <davem@...emloft.net>, rui.zhang@...el.com,
	jacob.jun.pan@...ux.intel.com,
	Mike Galbraith <bitbucket@...ine.de>,
	Ingo Molnar <mingo@...nel.org>, hpa@...or.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle implementations

On 11/20/2013 9:23 AM, Thomas Gleixner wrote:
> On Wed, 20 Nov 2013, Arjan van de Ven wrote:
>
>> On 11/20/2013 8:04 AM, Peter Zijlstra wrote:
>>> This does not fully preseve existing behaviour in that the generic
>>> idle cycle function calls into the normal cpuidle governed idle
>>> routines and should thus respect things like QoS parameters and the
>>> like.
>>
>>
>> NAK on the powerclamp side.
>>
>> powerclamp MUST NOT do that....
>> it is needed to go to the deepest state no matter what
>> (this is for when your system is overheating. there is not a lot of choice
>> here... alternative is an emergency reset that the hardware does for safety)
>
> So that whole machinery falls apart when the thing which is running on
> that hot core is a while(1) loop with a higher or equal FIFO priority
> than this thread. Even if you'd run at prio 99, then there is no
> guarantee that the cpu hog does not run with prio 99 as well and due
> to FIFO and being on the CPU it's not going to let you on.

the idea was to at least give people who know what they're doing a chance to run

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