[libcamera-devel] [PATCH v2 2/8] utils: ipc: proxy: Process pending messages

[Niklas Söderlund]

Hi Kieran and Laurent,

On 2021-03-12 05:47:21 +0000, Kieran Bingham wrote:
> From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> Events may be queued to the pipeline handler between the pipeline
> handler entering the ::stop() function, and before the call to stop the
> IPA has completed.
> 
> Handle these events by dispatching all pending messages at the proxy
> after the IPA has fully stopped.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  utils/ipc/generators/libcamera_templates/proxy_functions.tmpl | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl b/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl
> index 13dc8fdcab6e..8addc2fad0a8 100644
> --- a/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl
> +++ b/utils/ipc/generators/libcamera_templates/proxy_functions.tmpl
> @@ -31,6 +31,8 @@
>  	thread_.exit();
>  	thread_.wait();
>  
> +	Thread::current()->dispatchMessages(Message::Type::InvokeMessage);

Is this not similar to the issue we have in cam? What if the events 
processed here themself queue events will they be processed? I wonder if 
the cleanest solution to all this would be to stop accepting messages as 
the first step and return errors for all calls that would generate an 
event. After we stopped accepting new events we can process the queue 
until it's empty and once that is done we can stop the IPA.

Maybe it's overkill but at least we would make the race windows smaller 
and easier to reproduce when found as they would only depend on the 
content of the queue at stop().

> +
>  	running_ = false;
>  {%- endmacro -%}
>  
> -- 
> 2.25.1
> 
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-- 
Regards,
Niklas Söderlund