Re: [PATCH] cpufreq: Stop BUGing the system

From: Nishanth Menon
Date: Wed Dec 24 2014 - 10:06:16 EST

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@xxxxxx> 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.

Nishanth Menon
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