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SubjectRe: [PATCH v4 2/3] locking/mutex: Enable optimistic spinning of woken task in wait queue
On 08/08/2016 01:29 PM, Peter Zijlstra wrote:
> On Mon, Jul 18, 2016 at 04:39:25PM -0400, Waiman Long wrote:
>> Ding Tianhong reported a live-lock situation where a constant stream
>> of incoming optimistic spinners blocked a task in the wait list from
>> getting the mutex.
>>
>> This patch attempts to fix this live-lock condition by enabling the
>> woken task in the wait queue to enter into an optimistic spinning
>> loop itself in parallel with the regular spinners in the OSQ. This
>> should prevent the live-lock condition from happening.
> No, two spinners are not in fact starvation proof. It makes the reported
> life-lock scenario much less likely, but it does not guarantee anything.

Yes, I should have said reducing the chance of live-locking.

>> + /*
>> + * Optimistically spinning on the mutex without the wait lock
> There should either be a '.' at the end of that line, or the next line
> should not start with a capital.
>
> Also, I don't see how the two sentences are related, should they be in
> the same paragraph?

Sorry for the missing '.', and I will split it into 2 paragraphs.

Cheers,
Longman

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