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SubjectRe: [PATCH 19/21] cpuidle: create list of registered drivers
On 09/26/2013 08:17 AM, Viresh Kumar wrote:
> On 26 September 2013 04:00, Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
>> If you introduce a list, you will have to introduce a lock to protect
>> it.
>
> I missed it, should have added that :)
>
>> This lock will be in the fast path cpuidle_idle_call with the
>> get_driver function and conforming to the comment: "NOTE: no locks or
>> semaphores should be used here".
>>
>> A lock has been introduced in this function already and the system hangs
>> with 1024 cpus.
>
> Hmm... I see.. I didn't knew about this expectation.. What about a rcu
> read/write lock? As far as I know its too lightweight... Can we have that
> in fast path?

Nope, we can't use rcu in the idle path :)

http://lists.infradead.org/pipermail/linux-arm-kernel/2012-February/083054.html


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