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SubjectRe: [PATCH 0/3] coupled cpuidle state support
On 12/21/2011 10:40 AM, Colin Cross wrote:

>> this smells fundamentally racey to me; you can get an interrupt one
>> cycle after you think you're done, but before the last guy enters WFI...
>>
>> how do you solve that issue ?
>
> All the cpus have interrupts off when they increment the counter, so
> they cannot receive an interrupt. If an interrupt is pending on one
> of those cpus, it will be handled later when WFI aborts due to the
> pending interrupt.

... but this leads to cases where you're aborting before other cpus are
entering..... so your "last guy in" doesn't really work, since while cpu
0 thinks it's the last guy, cpu 1 is already on the way out/out
already... (heck it might already be going back to sleep if your idle
code can run fast, like in the size of a cache miss)


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