CC2340R5: How to create a non-blocking message queue?

Shuyang Zhong

Part Number: CC2340R5

I'm trying to create a non-blocking message queue by changing attr.mq_flags to O_NONBLOCK in BLEAppUtil_createQueue(), but it did not seem to work. The queue still blocked when it was full, and when I debugged into mq_open(), I found that msgQueueDesc->flags was 0, not the expected O_NONBLOCK.

Does the BLEAppUtil APIs support to create a non-blocking queue? If yes, how to make the queue non-blocking?

Best regards,

Shuyang

over 2 years ago

0 Clément over 2 years ago

TI__Guru** 101540 points

Hi Shuyang,

Thank you for reaching out.
To be sure I understand properly, can you please confirm you expect the queue to return an error when trying to enqueue a message while not having enough memory. Is it correct?

Best regards,

0 Shuyang Zhong over 2 years ago in reply to Clément

TI__Expert 5115 points

Yes, that is what I’m expecting.

Regards,

Shuyang

0 Clément over 2 years ago in reply to Shuyang Zhong

TI__Guru** 101540 points

Hi Shuyang,

It seems BLEAppUtil_createQueue() forces the use of a blocking queue.This means we have not tested the code for non-blocking queues, but you can run a test.

I would suggest you alter the BLEAppUtil_createQueue() function as following for a test:

static bStatus_t BLEAppUtil_createQueue(void)
{
     struct mq_attr attr;

     //attr.mq_flags = 0; //Blocking
     attr.mq_flags = O_NONBLOCK; //Non-blocking
     attr.mq_curmsgs = 0;
     attr.mq_maxmsg = 8;
     attr.mq_msgsize = sizeof(BLEAppUtil_appEvt_t);

     /* Create the message queue */
     BLEAppUtil_theardEntity.queueHandle = mq_open("BLEAppUtil_theardQueue", O_CREAT , 0, &attr);

     if (BLEAppUtil_theardEntity.queueHandle == (mqd_t)-1)
     {
         return FAILURE;
     }
     return SUCCESS;
}

Best regards,

0 Shuyang Zhong over 2 years ago in reply to Clément

TI__Expert 5115 points

Hi Clement,

Thanks for the reply. I did some tests and actually setting mq_flags = O_NONBLOCK will not work, because mq_flags is ignored when O_CREAT is true. This is from POSIX document:

Following the document, I used O_NONBLOCK along with O_CREAT as the oflags parameter into mq_open(), from my test this works. When the message queue is full and user tries to put another message into the queue, it returns EAGAIN instead of blocking the call.

Maybe the comment in BLEAppUtil_createQueue should be modified to avoid misguiding customers to believe changing mq_flags will create a non-blocking queue?

attr.mq_flags = 0; //Blocking

Best regards,

Shuyang

0 Clément over 2 years ago in reply to Shuyang Zhong

TI__Guru** 101540 points

Hi Shuyang,

Great findings, thank you for sharing!

I have reported your suggestions.

Thank you for helping us improving our product.

Kind regards,

Bluetooth®︎

Bluetooth forum

CC2340R5: How to create a non-blocking message queue?