MPCI not returning memory

[Sebastian Huber]

On 31/01/2019 13:41, Andres Monteverde wrote:
> Hi Sebastian, Thank you for your prompt response.
>
> > I don't think this is correct. If you call _MPCI_Send_request_packet(),
> > then the ownership of this packet is transferred to the implementation
> > of this function. With the shared memory driver, the packet is freed by
> > the receiver, see Shm_Free_envelope()."
>
> If you think that it's not correct, we can move the returning of the 
> packet inside _MPCI_Send_request_packet() but the reason why we return 
> the packet outside _MPCI_Send_request_packet() is because we were 
> focalized in queue behaviour and a change inside 
> _MPCI_Send_request_packet() is a broad solution with an unknown effect 
> for the test.
>
> Regarding "the packet is freed by the receiver, see 
> Shm_Free_envelope()", by looking at the code and running the code step 
> by step with jtag, the core0 (the owner of the queue) does not return 
> the packet in any case.
> The core0 MPCI handler for the receive request is:
>
> _Message_queue_MP_Process_packet()
> case MESSAGE_QUEUE_MP_RECEIVE_REQUEST:
>
>       the_packet->Prefix.return_code = rtems_message_queue_receive(
>         the_packet->Prefix.id,
>         the_packet->Buffer.buffer,
>         &the_packet->size,
>         the_packet->option_set,
>         the_packet->Prefix.timeout
>       );
>
>       if ( the_packet->Prefix.return_code != RTEMS_PROXY_BLOCKING )
>         _Message_queue_MP_Send_response_packet(
>           MESSAGE_QUEUE_MP_RECEIVE_RESPONSE,
>           the_packet->Prefix.id,
>           _Thread_Executing
>         );
>       break;
>
> The core1 MPCI handler for the receive response is:
>
> _Message_queue_MP_Process_packet()
> case MESSAGE_QUEUE_MP_RECEIVE_RESPONSE:
>
>       the_thread = _MPCI_Process_response( the_packet_prefix );
>
>       if (the_packet->Prefix.return_code == RTEMS_SUCCESSFUL) {
>         *(size_t *) the_thread->Wait.return_argument =
>            the_packet->size;
>
>         _CORE_message_queue_Copy_buffer(
>           the_packet->Buffer.buffer,
> the_thread->Wait.return_argument_second.mutable_object,
>           the_packet->size
>         );
>       }
>
>       _MPCI_Return_packet( the_packet_prefix );
>       break;
>
> As far as i understand is the core 1 who frees the packet.

Yes, this is also my understanding.

> And in case of a timeout waiting at the queue, there is no response at 
> all from core 0 so there's no return for the allocated packet nor the 
> proxy.

These are probably two independent problems.

Core 1 must still receive this packet at some time and free it.

The lost proxy in case of a timeout is another issue.

I don't have time to look into the details at the moment.

-- 
Sebastian Huber, embedded brains GmbH

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