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POWeird behavior of gettimeofday
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copied!<p>I would like to obtain the elapsed time between one thread enters to the Critical Zone and the other takes the permision to enter in the same Critical Zone on ARM CortexA8. For this I have been using the function gettimeofday() in C.</p> <pre><code> void *Thread1_Routine (); //Create the Semaphore void *Thread2_Routine (); //Wait for Thread1_Routine's Semaphore void configured_malloc_behavior(); void Calc_Dif_Time (struct timeval *time1,struct timeval *time2); //Definition to represent the time typedef struct te_tim96 { int64_t sec; int32_t usec; }te_tim96; //Variables to save the time struct timeval t1,t2; //Variable to control the order enter Critical zone char lock=0; int count=0; //Variable to make the create the mutex pthread_mutex_t mutex; int main (void) { //Variables define threads pthread_t threadadd1, threadadd2; pthread_attr_t attr1, attr2; struct sched_param p1, p2; //Configured malloc behavior configured_malloc_behavior(); //Init the Thread pthread_mutex_init(&mutex, NULL); //Define Threads pthread_attr_init(&attr1); pthread_attr_init(&attr2); //Thread1 pthread_attr_setschedpolicy(&attr1, SCHED_FIFO); p1.sched_priority= 98; //This is lower than Thread2 pthread_attr_setschedparam(&attr1, &p1); //Thread2 pthread_attr_setschedpolicy(&attr2, SCHED_FIFO); p2.sched_priority= 99; pthread_attr_setschedparam(&attr2, &p2); //End define Threads //Init the gpio63 as Output do Stuff() //Create the threads pthread_create(&threadadd1,&attr1,&Thread1_Routine, NULL); pthread_create(&threadadd2,&attr2,&Thread2_Routine, NULL); //Wait to end the Threads () pthread_join(threadadd1, NULL); pthread_join(threadadd2, NULL); return 0; } //Thread Producer void *Thread1_Routine (void) { //Variable to write in gpio/value char value=1; while (count<MAXCOUNT) { sleep (3); pthread_mutex_lock(&mutex); lock=lock+1; //Increment variable lock to indicate that the Thread Producer was done. gettimeofday(&t1, NULL); pthread_mutex_unlock(&mutex); } pthread_exit(NULL); } //Thread Consumer void *Thread2_Routine (void) { //Variable to write in gpio/value char value=0; while (count<MAXCOUNT) { //Wait for the semaphore is free!!!!! while (lock=0); pthread_mutex_lock(&mutex); lock=lock-1; //Decrement variable lock to indicate that the Thread Producer was done. gettimeofday(&t2, NULL); Calc_Dif_Time(&t1, &t2); //Function to calculate the latency and plot it pthread_mutex_unlock(&mutex); count++; //To incremate the count of how many time goes the thread are made } pthread_exit(NULL); } void Calc_Dif_Time (struct timeval *time1,struct timeval *time2) { struct te_tim96 Tmeasure1, Tmeasure2; double Elapsedtime; //TmeasureY=tY Tmeasure1.sec=(*time1).tv_sec; Tmeasure1.usec=(*time1).tv_usec; Tmeasure2.sec=(*time2).tv_sec; Tmeasure2.usec=(*time2).tv_usec; //Calculate //Part in sec to miliseconds Elapsedtime=(Tmeasure2.sec-Tmeasure1.sec)*1000; //Part in usec to miliseconds Elapsedtime+=(Tmeasure2.usec-Tmeasure1.usec)*0.001; //Work with the rest of the division to convert usec to miliseconds printf("Time to create the Semaphore[%lld.%6ld] Time to take the Semaphore[%lld.%6ld] Elapsed Time [%f ms]\n", Tmeasure1.sec, Tmeasure1.usec, Tmeasure2.sec, Tmeasure2.usec, Elapsedtime); Elapsedtime=0; //Reset Elapsedtime to the next measure } </code></pre> <p>The program is without error, but my problem, when I execute it, is that the console show the following result:</p> <blockquote> <p>./R_T_Measure4</p> <p>Time to create the Semaphore[0. 0] Time to take the Semaphore[4878.153276] Elapsed Time [4878153.276000 ms]</p> <p>Time to create the Semaphore[0. 0] Time to take the Semaphore[4878.153886] Elapsed Time [4878153.886000 ms]</p> </blockquote> <p>This result shows how I might that the t1 variable is not pointed well or it is restarted. But I don't know that I am overlooking in this case because t2 works well.</p> <p>Any help will be grateful</p> <p>-Regards</p>

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