I have a situation where the programme counter(PC) shows
that vxworks msgQreceive function has been called by task A
and Q is full, still I am not picking up the messages. There
is no other task registered to receive messages from this Q.
The sending task B, which is ISR in this case, is getting
timedout everytime it tries posting new message in it. A's
state is PEND which means I am waiting for some resource to
get free but PC shows I have called vxworks msgQReceive and
currently at qJobget+0x018 location. There seems to be two
causes now(identified by me): either vxworks qjobget task is
not able to do semTake or no messages in Q. But Q is full
and semTake failure seems unlikely(though I dont have a
mechanism to check so).

Besides explaining root cause for above, can anyone suggest
how to get my task in READY state again? I also tried
flushing the Q; on doing this, more messages get posted in Q
but A still doesnt pick up any :(

Answer Posted / gaurav srivastava

That is very strange , in your case the problem does not
seem to be the queue or msgQRecieve .I would go through the
following checklist :

1)What is the priority given to task A ? Is it high enough
when compared to other coexisting tasks ? If the priority
is very low then A wouldnt get executed often enough to
clear the queue (with task A being the only reader) , the
queue would get full and B would time out if it is
WAIT_FOREVER .

2)Make sure you are reading from the right queue.

I can't think of anything else , please let me know if you
have already found a solution to your problem.

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