How to start two threads at the same time

Question

Hi there,
  I want to include multithreading in the CVI program. I have two tasks which has no dependence between them, so I would like to start two threads for perform the tasks. I follow the introduction http://www.ni.com/white-paper/3663/en/ to start my code. In my code, I add a command button, when it is pressed, I create two threads to perform the tasks. In each task, I have a big loop and in each iteration, I use ProcessSystemEvents to avoid no response on system message. But it doesn't work actually, the program suspended. I wonder must I initialize the threads in main. I am looking for a way to start the threads in the callback function for a button since I am not starting those threads at the beginning but while it is triggered.
the main frame of the code looks
int CVICALLBACK Test1(void *functionData)
{ int i=0;
for (i = 0; i<100000; i++) {ProcessSystemEvents();}
return 0;
int CVICALLBACK Test2(void *functionData)
int i = 0;
for (i = 0; i<100000; i++) {ProcessSystemEvents();}
return 0;
int CVICALLBACK cmdcb(int panel, int control, int event, void *callbackData, int eventData1, int eventData2)
{ int threadID1, threadID2;
if (event==EVENT_COMMIT)
SetPanelAttribute(panelHandle, ATTR_DIMMED, 1);
CmtScheduleThreadPoolFunction(DEFAULT_THREAD_POOL_HANDLE, Test1, NULL, &threadID1);
CmtScheduleThreadPoolFunction(DEFAULT_THREAD_POOL_HANDLE, Test2, NULL, &threadID2);
CmtWaitForThreadPoolFunctionCompletion (DEFAULT_THREAD_POOL_HANDLE, threadID1, 0);
CmtWaitForThreadPoolFunctionCompletion (DEFAULT_THREAD_POOL_HANDLE, threadID2, 0);
return 0;
Attachments:
TestThread.zip ‏239 KB

Answer 1

In my opinion your threads may be simply lasting longer than expected due to an incorrect sleep policy of threads paired with with ProcessSystemEvents () in the loop.
I made up a quick example that shows this behaviour: playing with "Do not sleep" and "Call ProcessSystemEvents" options you can see how threads execute.
BTW: do not forget to release the thread function IDs at the end of functions.
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Attachments:
thread.zip ‏7 KB