thread pool ownership

[Wolfgang]

Hi,

when shutting down a multithreaded application, the main thread schedules functions that will terminate the secondary threads, using PostDeferredCallToThread ( callback_function, callback_data, thread_id ) in a loop over all seconadry threads.

This works fine, and I can close the application as intended. 

However, if I add another line to the loop, as recommended by the NI sample programs, CmtWaitForThreadPoolFunctionCompletion ( pool_handle, thread_function_id, OPT_TP_PROCESS_EVENTS_WHILE_WAITING ),

I receive an error message:

The function ID you passed is owned by the thread pool. This operation can only be performed on a function ID that you own.

This loop is initiated by the main thread, so how can the thread pool own a function ID?

I am using the pool handle that I obtained from the CmtNewThreadPool and not the default thread pool handle.

Thanks (and no more posts today)

Wolfgang

[cdk52]

Hi Wolfgang.

Keep in mind that callback_function you specify in the CmtWaitForThreadPoolFunctionCompletion() call will not execute until the thread becomes idle, so thread_function_id will not be valid.

Here is a simple approach that works for me:

int Shutdown;    // global variable

int myThreadPool;

int main (int argc, char *argv[])
{

  Shutdown = 0;

  CmtNewThreadPool(nThreads, &myThreadPool);

  ...

  // Signal threads - application is closing

  Shutdown = 1; 

  CmtDiscardThreadPool(myThreadPool);  // Blocks until all threads in thread pool are idle

  return 0;

}

Each thread function (including those running in the default thread pool) includes lines similar to:

  while(!Shutdown && someOtherCondition)

    ProcessSystemEvents();

  return 0;

Colin.

Message Edited by cdk52 on 05-11-2009 10:07 AM

[Wolfgang]

Hi Colin,

sounds reasonable, but still this answer is confusing me because...

Recently, I have obtained a nice sample code from Roberto (here http://forums.ni.com/ni/board/message?board.id=180&message.id=41004#M41004)

which does exactly (?!) the same thing:

  PostDeferredCallToThread (QuitUICallback, 0, threadID);
  CmtWaitForThreadPoolFunctionCompletion (poolHandle, fnID, OPT_TP_PROCESS_EVENTS_WHILE_WAITING);

and it worked just fine...

Wolfgang

[cdk52]

Hello Wolfgang.

My apologies. When you wrote "...the main thread schedules functions..." I assumed that you were calling CmtScheduleThreadPoolFunction() or CmtScheduleThreadPoolFunctionAdv() - I ignored "...using PostDeferredCallToThread()...".

I looked at the modified MultiPanel sample provided by Roberto. If your code is similar in structure, I can see no reason why it should not work as you expect.

Does your code include any calls to CmtReleaseThreadPoolFunctionID()? I imagine that if you call CmtWaitForThreadPoolFunctionCompletion() after the function ID has been released, you will generate an error.

Good luck.

Colin.

[Wolfgang]

Hi Colin,

Thanks for suggesting to check for CmtReleaseThreadPoolFunctionID. Indeed I had such a call, but even if commenting it out the error remains the same. By the way, when calling CmtReleaseThreadPoolFunctionID instead of CmtWaitForThreadPoolFunctionCompletion, I receive the same error...?? This seems to suggest that something with my pool handle is wrong, but I make use of it only once, when starting the secondary threads from the primay threads using

CmtScheduleThreadPoolFunctionAdv ( pool_handle, thread_function, thread_function_data, csi_process_class, callback_function,

( EVENT_TP_THREAD_FUNCTION_BEGIN || EVENT_TP_THREAD_FUNCTION_END ), 0, RUN_IN_SCHEDULED_THREAD, NULL )

I can't see anything wrong here... 

Wolfgang