Re: [PATCH 6/8] virtio-blk: mark IO_CODE functions

[Emanuele Giuseppe Esposito]

Am 05/07/2022 um 16:39 schrieb Stefan Hajnoczi:
> On Thu, Jun 09, 2022 at 10:37:25AM -0400, Emanuele Giuseppe Esposito wrote:
>> Just as done in the block API, mark functions in virtio-blk
>> that are called also from iothread(s).
>>
>> We know such functions are IO because many are blk_* callbacks,
>> running always in the device iothread, and remaining are propagated
>> from the leaf IO functions (if a function calls a IO_CODE function,
>> itself is categorized as IO_CODE too).
>>
>> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
>> ---
>>  hw/block/dataplane/virtio-blk.c |  4 ++++
>>  hw/block/virtio-blk.c           | 35 +++++++++++++++++++++++++++++++++
>>  2 files changed, 39 insertions(+)
> 
> The definition of IO_CODE() is:
> 
>   I/O API functions. These functions are thread-safe, and therefore
>   can run in any thread as long as the thread has called
>   aio_context_acquire/release().
> 
> I'm not sure it matches with the exact semantics you have in mind. Are
> they really allowed to be called from any thread and even from multiple
> threads? Or maybe just from the BlockBackend's AioContext thread?

I think it is just from the BlockBackend's AioContext thread. But I
classified blk_* functions as IO_CODE.

What is your opinion on that?

> 
> We need to be very careful to define these terms precisely and avoid
> applying them in cases that are similar but different as that will cause
> problems in the future.
> 
> Otherwise:
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>