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POUnpredictable behavior with SetEvent and WaitForMultipleObjects
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  1. POUnpredictable behavior with SetEvent and WaitForMultipleObjects
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    copied!<p>I am attempting to use <code>SetEvent</code> and <code>WaitForMultipleObjects</code> so I wrote a couple of functions that I wanted to synchronize using Events. I want the first function to execute, and then signal the second function to execute, which in turn signals the first function to execute again etc. </p> <p>Two events were created, one initialized to a signaled state, the other unsignaled. The only way I can get the execution to flow as expected is when putting the each thread to sleep for 10 ms. I read about some caveats about using SetEvent: <a href="http://cboard.cprogramming.com/windows-programming/100818-setevent-resetevent-3.html" rel="nofollow">http://cboard.cprogramming.com/windows-programming/100818-setevent-resetevent-3.html</a></p> <p>My question is must I put my threads to sleep because these function calls require extra time to actually signal the events? When debugging sometimes an event that is set still remains unsignalled. I verify this using process explorer. My code basically looks like this:</p> <p>in the main:</p> <pre><code>//1. FinCalcpidUpdatestruct &lt;&lt; initialize to unsignalled //2. FinUpdatestructCalcpid &lt;&lt; initialize to signalled FinCalcpidUpdatestruct = CreateEvent (NULL, FALSE, FALSE, TEXT("FinCalcpidUpdatestruct")); FinUpdatestructCalcpid = CreateEvent (NULL, FALSE, TRUE, TEXT ("FinUpdatestructCalcpid")); void function1() { int n; int noGoCode; n=0; noGoCode = 0; while(1) { //Sleep(10); noGoCode = WaitForSingleObject (FinCalcpidUpdatestruct, INFINITE); if (noGoCode == WAIT_OBJECT_0) { //wait for FinCalcpidUpdatestruct to be signalled BufferOut[n] = pid_data_array -&gt; output; //signal FinUpdatestructCalcpid if(!SetEvent (FinUpdatestructCalcpid)) printf("Couldn't set the event FinUpdatestructCalcpid\n"); else{ printf("FinUpdatestructCalcpid event set\n"); Sleep(10); } } else printf("error\n"); } } void function2() { int nGoCode = 0; while(1) { //wait for FinUpdatestructCalcpid to be signalled // Sleep(10); nGoCode = WaitForSingleObject (FinUpdatestructCalcpid, INFINITE); if (nGoCode == WAIT_OBJECT_0) { if(!SetEvent (FinCalcpidUpdatestruct)) printf("Couldn't set the event FinCalcpidUpdatestruct\n"); else{ printf("FinCalcpidUpdatestruct event set\n"); Sleep(10); } } else printf("error\n"); }//end while(1) </code></pre> <p>If the sleep is not used then sometimes the same function will run through the while loop a couple of times instead of ping ponging back and forth between the two functions. Any ideas?</p>
 

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