Re: v3.13.5 intel_pstate: cpufreq: __cpufreq_add_dev: ->get() failed

[Dirk Brandewie <dirk.brandewie@gmail.com>]

On 03/11/2014 01:20 PM, Rafael J. Wysocki wrote:
> On Tuesday, March 11, 2014 10:58:59 AM Dirk Brandewie wrote:
>> Hi Patrick,
>>
>> Sorry for the slow response you caught me taking a few days off :-)
>>
>> On 03/07/2014 07:49 AM, Patrik Lundquist wrote:
>>> Hi,
>>>
>>> booting 3.13.5 on a dual socket Ivy Bridge-EP resulted in this error:
>>>
>>> [    0.194139] smpboot: CPU0: Intel(R) Xeon(R) CPU E5-2687W v2 @
>>> 3.40GHz (fam: 06, model: 3e, stepping: 04)
>>> ...
>>> [    0.246755] x86: Booting SMP configuration:
>>> [    0.250935] .... node  #0, CPUs:        #1  #2  #3  #4  #5  #6  #7
>>> [    0.357648] .... node  #1, CPUs:    #8  #9 #10 #11 #12 #13 #14 #15
>>> [    0.553293] x86: Booted up 2 nodes, 16 CPUs
>>> [    0.557666] smpboot: Total of 16 processors activated (108850.19 BogoMIPS)
>>> ...
>>> [    5.210204] Intel P-state driver initializing.
>>> [    5.232407] Intel pstate controlling: cpu 0
>>> [    5.253628] Intel pstate controlling: cpu 1
>>> [    5.274899] cpufreq: __cpufreq_add_dev: ->get() failed
>>> [    5.294856] Intel pstate controlling: cpu 2
>>> [    5.313553] Intel pstate controlling: cpu 3
>>> [    5.332526] Intel pstate controlling: cpu 4
>>> [    5.352347] Intel pstate controlling: cpu 5
>>> [    5.372112] Intel pstate controlling: cpu 6
>>> [    5.391097] Intel pstate controlling: cpu 7
>>> [    5.410272] Intel pstate controlling: cpu 8
>>> [    5.429092] Intel pstate controlling: cpu 9
>>> [    5.447714] Intel pstate controlling: cpu 10
>>> [    5.465872] Intel pstate controlling: cpu 11
>>> [    5.482942] Intel pstate controlling: cpu 12
>>> [    5.498414] Intel pstate controlling: cpu 13
>>> [    5.513586] Intel pstate controlling: cpu 14
>>> [    5.529200] Intel pstate controlling: cpu 15
>>>
>>> CPU 1 is alive and well but missing the cpufreq driver. The system is
>>> running fine otherwise.
>>
>> This is a regression introduced by commit
>> da60ce9f2fa cpufreq: call cpufreq_driver->get() after calling ->init()
>
> So the problem is that ->get() may return 0 in intel_pstate and that causes
> the core's _add function to abort?  That would mean sample->freq equal to 0,
> which shouldn't happen after intel_pstate_sample() called by intel_pstate_init_cpu().
>
> Or am I missing anything?
>

The problem is that the core has been running less than 1% of the time based on 
the absolute values of aperf/mperf and the second sample has not been taken to
get a more precise delta.

I thought about running sample twice during init but didn't want to propose it
until I made sure I was not going to break anything else.




second sample hasn't been taken
> Rafael
>