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Date: Tue, 17 Sep 2013 18:19:26 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC] [PATCHv10 00/31] aio / timers: Add
 AioContext timers and use ppoll
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, liu ping fan <qemulist@gmail.com>, Alex Bligh <alex@alex.org.uk>, MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>, rth@twiddle.net

Il 17/09/2013 18:09, Jan Kiszka ha scritto:
> On 2013-08-13 16:22, Stefan Hajnoczi wrote:
>> On Tue, Aug 13, 2013 at 03:45:44PM +0200, Jan Kiszka wrote:
>>> Yeah:
>>>
>>> -    /* No AIO operations?  Get us out of here */
>>> -    if (!busy) {
>>> +    /* early return if we only have the aio_notify() fd */
>>> +    if (ctx->pollfds->len == 1) {
>>>          return progress;
>>>      }
>>>
>>> So this is even worse for my use case.
>>
>> We can change the semantics of aio_poll() so long as we don't break
>> existing callers and tests.  It would make sense to do that after
>> merging the io_flush and AioContext timers series.
> 
> Need to pick up this topic again because above change is now mainline
> and breaks aio_poll-based timer threads:
> 
> How can we make progress with overcoming that check, at least for the
> timer thread use case? Additional argument "truly_block" for aio_poll?

I wonder if we still need that "if" at all.  Guys, do you remember what
it is good for? O:-)

Paolo