Re: [RFC PATCH 02/10] smp, cpu hotplug: Fix smp_call_function_*()to prevent CPU offline properly

[Srivatsa S. Bhat]

On 12/05/2012 05:09 AM, Rusty Russell wrote:
> "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> writes:
>> From: Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx>
>>
>> With stop_machine() gone from the CPU offline path, we can't depend on
>> preempt_disable() to prevent CPUs from going offline from under us.
> 
> Minor gripe: I'd prefer this paragraph to use the future rather than
> past tense, like: "Once stop_machine() is gone ... we won't be able to
> depend".
> 

Fixed in the new version.

> Since you're not supposed to use the _stable() accessors without calling
> get_online_cpus_stable_atomic(), why not have
> get_online_cpus_stable_atomic() return a pointer to the stable cpumask?
> (Which is otherwise static, at least for debug).
>

We don't have to worry about this now because the new version doesn't
use stable cpumask.
 
> Might make the patches messier though...
> 
> Oh, and I'd love to see actual benchmarks to make sure we've actually
> fixed a problem with this ;)
> 

Of course :-) They will follow, once we have a proper implementation
that we are happy with :-)

Regards,
Srivatsa S. Bhat

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