Issues with task priorities in NDK

Hi,

A few things to check:
1.  What Tasks are in your system and what are their priorities relative to each other?  A ROV screen shot when the failure occurs would be nice!

2.  Make sure the dummy for-loop does not get optimized out.  You can do this by having a function call in the for-loop or a volatile variable.  Basically, make sure that you are actually spending some cycles spinning.

Judah

Thanks Judah, here is their response:

I do have code in the for loop so it's not optimized out. I also have a printf statement after each message is sent so I can see the delay loop is taking effect.

I've attached the ROV screenshots in both the working case (TxDataTask is priority 1) and not working (TxDataTask is priority 2). I can see that the NetworkTask priority has dropped to 1. Does the task normally change priorities on the fly like that?

Working Case ROV - Tasks snapshot

Not-Working Case ROV - Tasks Snapshot:

I know that the NetworkTask priority does change on the fly.  The NetworkTask priorty being 1 seems like a problem to me.  I don't know the details of the NDK and my colleague who does know is out of the office today.  I will have to get back to you.

It looks like there's a priority inversion occurring.

Johannes said:

Not-Working Case ROV - Tasks Snapshot:

Has the stack been shut down at this point? (i.e. has NC_NetStart() returned?

The only place where the priority would drop to 2 is in the following code, which happens after the NetScheduler exits and the stack shut down and clean up code runs:

    TaskSetPri( TaskSelf(), OS_SCHEDULER_LOWPRI );

Steve

Stever, here is the latest findings:

No – the stack has not been shutdown. I was able to figure one thing out – the initial priority of the task seems to have an effect.

I have TaskCreate(&NetworkTask, “NetworkTask”, PRI, 4096,0,0,0); This task will setup the network (call NC_SystemOpen and NC_NetStart etc).

I am always using NC_PRIORITY_HIGH in the NC_SystemOpen call. When I’m observing the problematic behavior, I have PRI set to 1. If set PRI = NC_PRIORITY_HIGH (which is 8) then everything works as expected. I don’t know why the original priority of the task should matter since the call to NC_SystemOpen changes the priority of the task (which I see in the ROV and debugger). But in my failure case, I see the priority of the task return to the original value of PRI that I had it set to (in my case it was 1).  

regards -emil