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Date: Wed, 17 Jul 2013 10:11:07 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] [RFC] aio/async: Add timed bottom-halves
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To: Alex Bligh <alex@alex.org.uk>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, rth@twiddle.net

Il 17/07/2013 10:07, Alex Bligh ha scritto:
> Stefan,
> 
> --On 17 July 2013 11:02:30 +0800 Stefan Hajnoczi <stefanha@gmail.com>
> wrote:
> 
>> The steps to achieving this:
>>
>> 1. Drop alarm timers from qemu-timer.c and calculate g_poll() timeout
>>    instead for the main loop.
>>
>> 2. Introduce a per-AioContext aio_ctx_clock that can be used with
>>    qemu_new_timer() to create a QEMUTimer that expires during
>>    aio_poll().
>>
>> 3. Calculate g_poll() timeout for aio_ctx_clock in aio_poll().
> 
> A couple of questions:
> 
> 1. How would this work where the user has no main loop, e.g. qemu-img? A
>   block driver may well still need timers.

The block driver should only use aio_ctx_clock, and those _would_ be
handled in aio_poll().

> 3. Is it safe to anything you can do in a bh in a timer? IE are users every
>   going to need to schedule a bh from a timer? If so, this seems a bit
>   long winded for users that want bh functionality.

It is safe.

Paolo