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SubjectRe: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem to be held for duration of changing governors [v2]


On 10/13/2014 06:43 AM, Viresh Kumar wrote:
> On 1 August 2014 22:48, Stephen Boyd <sboyd@codeaurora.org> wrote:
>> On 08/01/14 03:27, Prarit Bhargava wrote:
>>>
>>> Can you send me the test and the trace of the deadlock? I'm not creating it with:
>>>
>>
>> This was with conservative as the default, and switching to ondemand
>>
>> # cd /sys/devices/system/cpu/cpu2/cpufreq
>> # ls
>> affected_cpus scaling_available_governors
>> conservative scaling_cur_freq
>> cpuinfo_cur_freq scaling_driver
>> cpuinfo_max_freq scaling_governor
>> cpuinfo_min_freq scaling_max_freq
>> cpuinfo_transition_latency scaling_min_freq
>> related_cpus scaling_setspeed
>> scaling_available_frequencies stats
>> # cat conservative/down_threshold
>> 20
>> # echo ondemand > scaling_governor
>>
>> ======================================================
>> [ INFO: possible circular locking dependency detected ]
>> 3.16.0-rc3-00039-ge1e38f124d87 #47 Not tainted
>> -------------------------------------------------------
>> sh/75 is trying to acquire lock:
>> (s_active#9){++++..}, at: [<c0358a94>] kernfs_remove_by_name_ns+0x3c/0x84
>
> Can you please retry this on mainline? I wasn't able to reproduce it
> now over 3.17.
> I am trying this on Exynos b.L implementation..

I have 100% reproducibility on latest mainline.

Viresh, please see my next post on the locking issues in cpufreq.

P.

>


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