[solved] can't change scaling governor

[matroskin]

Hi
I'm trying to change scaling governor and get "invalid argument" error.. Actually I can't change any value under cpufreq directory. While I run ubuntu on that comp, everything works.

Here is a bash session

[netixen]

Try

[Roman_Gruber]

for some reason only cpupower works here.

example

[matroskin]

Thank you for the answers, but both cpupower and cpufreq-set fails
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[Roman_Gruber]

well you could compare ubutnu kernel config with your current kernel config and check wheres the difference.

also check which modules are loaded in both distributions and compare.

also maybe a userspace issue. ... could be /dev related too but thats just a guess

[matroskin]

Well, I think I came close to the answer - the config is ok, the combination of patches brings problem

I run kernel with aufs and RT patch
kernel with RT patch alone works ok
Kernel with aufs patch alone works ok
The problem arise only on a kernel with both patches
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[matroskin]

The final answer is this: the RT kernel prevents changing scaling governor

Here is an explanation found on RT mailing list discussing exactly same problem
Thread http://www.spinics.net/lists/linux-rt-users/msg12170.html

They dug into the code and found that RT patch holds additional lock preventing taking semaphore needed to change a governor. Calling code returns EINVAL if taking semaphore fails - this is the reason for "invalid argument" error

Details are here http://www.spinics.net/lists/linux-rt-users/msg12207.html
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