Re: [Qemu-devel] [RFC] [PATCHv10 00/31] aio / timers: Add AioContext timers and use ppoll

[Alex Bligh]

Paolo,

On 18 Sep 2013, at 08:57, Paolo Bonzini wrote:

> Il 17/09/2013 19:32, Alex Bligh ha scritto:
>> 
>> On 17 Sep 2013, at 18:04, Paolo Bonzini wrote:
>> 
>>> Alex, what's missing before block.c and QED can use aio_timer_new on
>>> the main AioContext, instead of timer_new?
>> 
>> If we assume at this stage the threading is no different, very little
>> I think. Off the top of my head it should be a case of:
>> 
>> 1. Audit timer routines to ensure they are safe to call from
>>   inside aio_poll rather than mainloop. EG if there is a timer
>>   routine that itself calls aio_poll, that would presumably
>>   be bad. A quick check suggests we need to think about the
>>   coroutine stuff carefully here if we don't want recursion.
>> 
>> 2. Replace timer_new by aio_timer_new
>> 
>> 3. Cross fingers and hope for the best.
> 
> Yes, that was my understanding too.  Can we do it for 1.7?

Don't see why not. I'd need to immerse myself in coroutines
and understand how they all work and am off on vacation for
a week tomorrow, so someone else (Stefan?) may be able to
do it faster than me. I expect it's just a case of saying
"yup, that will work" for someone who knows the co-routine
call-graph. If not, I'll have a look at it on my return.

>> I think block/iscsi.c needs doing too.
>> 
>> If we're worried about threading changes, then I'm not sure
>> how much of the thread safety stuff has been pulled to master,
>> plus someone needs to audit thread safety for use_icount=1.
> 
> Nothing has.  use_icount=1 is still on my todo list.


Rather you than me!

-- 
Alex Bligh