Re: [patch] aio: add per task aio wait event condition

[Zach Brown]

On Jan 2, 2007, at 5:50 PM, Chen, Kenneth W wrote:

> Zach Brown wrote on Tuesday, January 02, 2007 5:24 PM
> > > That is not possible because when multiple tasks waiting for
> > > events, they
> > > enter the wait queue in FIFO order, prepare_to_wait_exclusive() does
> > > __add_wait_queue_tail().  So first io_getevents() with min_nr of 2
> > > will be woken up when 2 ops completes.
> >
> > So switch the order of the two sleepers in the example?
>
> Not sure why that would be a problem though:  whoever sleep first will
> be woken up first.

Why would the min_nr = 3 sleeper be woken up in that case?  Only 2  
ios were issued.

Maybe the app was relying on the min_nr = 2 completion to issue 3  
more ios for the min_nr = 3 sleeper, who knows.

> Before I challenge that semantics, I want to mention that in current
> implementation, dribbling AIO events will be distributed in round  
> robin
> fashion to all pending tasks waiting in io_getevents.

Yeah, don't misunderstand me -- we agree that the current situation  
is bad.

>   In the example you
> gave earlier, task with min_nr of 2 will be woken up after 4 completed
> events.

I only gave 2 ios/events in that example.

Does that clear up the confusion?

- z
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