Re: [Qemu-devel] [PATCH v4 4/5] mirror: follow AioContext change gracefully

[Paolo Bonzini <pbonzini@redhat.com>]

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On 16/06/2016 12:17, Stefan Hajnoczi wrote:
> On Wed, Jun 15, 2016 at 10:57:49AM +0200, Paolo Bonzini wrote:
>> On 14/06/2016 20:17, Stefan Hajnoczi wrote:
>>> +/* There is no matching mirror_resume() because mirror_run() will begin
>>> + * iterating again when the job is resumed.
>>> + */
>>> +static void mirror_pause(BlockJob *job)
>>> +{
>>> +    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
>>> +
>>> +    while (s->in_flight > 0) {
>>> +        aio_poll(blk_get_aio_context(job->blk), true);
>>> +    }
>>
>> This is calling aio_poll from a coroutine, which is ugly -- see Fam's
>> recent introduction of bdrv_co_drain.  I think this should call
>> mirror_drain instead.
> 
> This is not called from coroutine context, so I couldn't use
> mirror_drain().
> 
> BlockJobDriver->pause() and attached_aio_context() are both not
> coroutine_fn.  That's because bdrv_attach_aio_context() is not
> coroutine_fn and can be called from a monitor command or device
> emulation code.

But mirror_pause is only called from block_job_pause_point, isn't it?
And block_job_pause_point is a coroutine_fn.

I think what you say was true for v3, though.

Paolo


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