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SubjectRe: [tip:x86/idle] x86, hotplug: Move WBINVD back outside the play_dead loop
On 09/17/2010 05:48 PM, Venkatesh Pallipadi wrote:
>>
>> + wbinvd();
>> +
>> while (1) {
>> - mb();
>> - wbinvd();
>> __monitor(&current_thread_info()->flags, 0, 0);
>> mb();
>
>
> Just one observation. There are some CPUs with errata that need
> clflush before monitor. So, if that CPU wakesup spuriously it may have
> problem reentering idle. Not sure whether that will be a problem as
> that errata also depended on read happening on the flag. May be its
> better to do monitor (0, 0, 0).
>

It seems the easy way to deal with that would be to just add clflush
before monitor... it is *probably* redundant, but it should be safe to
do. It means depending on X86_FEATURE_CLFLUSH as well as
X86_FEATURE_MWAIT, but I don't think there is any x86 processor which
has MWAIT and not CLFLUSH, and I highly doubt there ever will be.

Does anyone see any downside?

-hpa


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