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SubjectRe: [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit
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On 06/07/17 12:15, Viresh Kumar wrote:
> On 06-07-17, 11:59, Juri Lelli wrote:
>> On 06/07/17 15:52, Viresh Kumar wrote:

[...]

>>
>> If that's the case I'm wondering however if we need explicit
>> synchronization though. Otherwise both threads can read the mask as
>> full, clear only their bits and not schedule the workfn?
>
> Maybe not as the policies are created one by one only, not concurrently.
>
>> But, can the policies be concurrently initialized? Or is the
>> initialization process serialized or the different domains?
>
> There can be complex cases here. For example consider this.
>
> Only the little CPUs are brought online at boot. Their policy is set and they
> are cleared from the cpus_to_visit mask. Now we try to bring any big CPU online
> and at the same time try changing min/max from sysfs for the LITTLE CPU policy.
>
> The notifier may get called concurrently here I believe and cause the problem I
> mentioned earlier.
>

I chatted with Juri and your proposed fix to do the unregister before
the free makes sense to us. Thanks for spotting this! I will change in
the next version.

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