Re: [KVM-RFC PATCH 1/2] eventfd: add an explicit srcu based notifier interface

Gregory Haskins
2009-06-18T22:47:29Z

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Davide Libenzi wrote:
> On Thu, 18 Jun 2009, Gregory Haskins wrote:
>
>
>> Davide Libenzi wrote:
>>
>>> On Thu, 18 Jun 2009, Gregory Haskins wrote:
>>>
>>>
>>>
>>>> Actually there is only one (the tx-thread) aside from the eventfd
>>>> imposed workqueue one. Incidentally, I would love to get rid of the
>>>> other thread too, so I am not just picking on eventfd ;). The other is
>>>> a lot harder since it has to update the virtio-ring and may need to page
>>>> in guest memory to do so.
>>>>
>>>>
>>> No, there is the interface rx softirq too, that makes two.
>>>
>> Actually, I believe you are mistaken. It normally executes the softirq
>> in interrupt context, not a thread.
>>
>> But I digress. Lets just shelve the SRCU conversation for another day.
>> It was my bad for introducing it now prematurely to solve a mostly
>> unrelated problem: the module-reference thing. I didn't realize the
>> SRCU change would be so controversial, and I didn't think to split
>> things apart as I have done today.
>>
>> But the fact is: I do not see any way to actually use your referenceless
>> POLLHUP release code in a race free way without doing something like I
>> propose in 3/4, 4/4. Lets keep the discussion focused on that for now,
>> if we could.
>>
>
> OK, since I got literally swamped by the amount of talks and patches over
> this theoretically simple topic, would you mind 1) posting the global
> patch over eventfd 2) describe exactly what races are you talking about
> 3) explain why this should be any concern of eventfd at all?
>
>
>
Yes, I can do that. Thanks Davide,

-Greg

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