Re: [KVM PATCH 2/3] eventfd: add a notifier mechanism

Gregory Haskins
2009-04-24T04:12:27Z

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Davide Libenzi wrote:
> On Thu, 23 Apr 2009, Gregory Haskins wrote:
>
>
>>> Take a look at init_waitqueue_func_entry(), in particula at that "func"
>>> parameter. Then look at how __wake_up_common() does its thing.
>>> You don't need to be "waiting" for our wakeup system to work. Callbacks
>>> works just fine, otherwise things like epoll could not work at all.
>>>
>>>
>> Yeah, I was looking at that this afternoon after you mentioned it. That
>> makes sense.
>>
>> As of right now the wqh is embedded in the eventfd, accessible only by
>> the .read() vtable entry. In order to do this as you suggest, I imagine
>> I need to slightly modify the eventfd interface to allow waiters other
>> than the embedded readers to join the wait-queue. How would you like to
>> see that interface look?
>>
>
> Actually, you need no changes in eventfd, since you can use its poll()
> directly, by dropping a callback entry.
> Take a look at how epoll does it in ep_insert()...
>
Ah! I just tried your suggestion and it was simple and it works. That
is brilliant.

I will post a follow-up v2 that drops patch 2/3. Thanks, Davide.

-Greg

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