linux-kernel - Re: [PATCH] cpufreq: Stop BUGing the system

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Date:	Wed, 24 Dec 2014 09:06:05 -0600
From:	Nishanth Menon <nm@...com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>
CC:	Kevin Hilman <khilman@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] cpufreq: Stop BUGing the system

On 12/18/2014 08:08 PM, Rafael J. Wysocki wrote:
> On Friday, December 19, 2014 07:11:19 AM Viresh Kumar wrote:
>> On 18 December 2014 at 20:19, Nishanth Menon <nm@...com> wrote:
>>> I can add "could be unstable" -> the point being there can be psuedo
>>> errors reported in the system - example - clock framework bugs. Dont
>>> just stop the boot. example: what if cpufreq was a driver module - it
>>> would not have rescued the system because cpufreq had'nt detected the
>>> logic - if we are going to force this on the system, we should probably
>>> not do this in cpufreq code, instead should be somewhere generic.
>>>
>>> While I do empathise (and had infact advocated in the past) of not
>>> favouring system attempting to continue at an invalid configuration and
>>> our attempt to rescue has failed - given that we cannot provide a
>>> consistent behavior (it is not a core system behavior) and potential of
>>> a false-postive (example clk framework or underlying bug), it should be
>>> good enough to "enhance" WARN to be "severe sounding enough" to
>>> flag it for developer and continue while keeping the system alive as
>>> much as possible.
>>
>> There is no way out for the kernel to know if its a false positive or a real
>> bug. And in the worst case, it can screw up a platform completely.
>>
>> I am still not sure if changing it to a WARN would be good idea.
>>
>> @Rafael: Thoughts ?
> 
> I'm a bit divided here.  On the one hand I don't like BUG_ON() as a rule and it
> is used in too many places where it doesn't have to be used.
> 
> On the other hand, in this particular case, I'm not sure if allowing the system
> to run without cpufreq when it might rely on it for CPU cooling, for one example,
> is a good idea.

but then, CPUFReq is not a mandatory feature - we could as well do the
same with CPU_FREQ disabled.

-- 
Regards,
Nishanth Menon
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