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POpthreads_setaffinity_np: Invalid argument?
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copied!<p>I've managed to get my pthreads program sort of working. Basically I am trying to manually set the affinity of 4 threads such that thread 1 runs on CPU 1, thread 2 runs on CPU 2, thread 3 runs on CPU 3, and thread 4 runs on CPU 4.</p> <p>After compiling, my code works for a few threads but not others (seems like thread 1 never works) but running the same compiled program a couple of different times gives me different results.</p> <p>For example:<br> hao@Gorax:~/Desktop$ ./a.out<br> Thread 3 is running on CPU 3<br> pthread_setaffinity_np: Invalid argument<br> Thread Thread 2 is running on CPU 2<br> hao@Gorax:~/Desktop$ ./a.out<br> Thread 2 is running on CPU 2<br> pthread_setaffinity_np: Invalid argument<br> pthread_setaffinity_np: Invalid argument<br> Thread 3 is running on CPU 3<br> Thread 3 is running on CPU 3<br> hao@Gorax:~/Desktop$ ./a.out<br> Thread 2 is running on CPU 2<br> pthread_setaffinity_np: Invalid argument<br> Thread 4 is running on CPU 4<br> Thread 4 is running on CPU 4<br> hao@Gorax:~/Desktop$ ./a.out<br> pthread_setaffinity_np: Invalid argument </p> <p>My question is "Why does this happen? Also, why does the message sometimes print twice?"</p> <p>Here is the code:</p> <pre><code>#define _GNU_SOURCE #include <stdio.h> #include <pthread.h> #include <stdlib.h> #include <sched.h> #include <errno.h> #define handle_error_en(en, msg) \ do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0) void *thread_function(char *message) { int s, j, number; pthread_t thread; cpu_set_t cpuset; number = (int)message; thread = pthread_self(); CPU_SET(number, &cpuset); s = pthread_setaffinity_np(thread, sizeof(cpu_set_t), &cpuset); if (s != 0) { handle_error_en(s, "pthread_setaffinity_np"); } printf("Thread %d is running on CPU %d\n", number, sched_getcpu()); exit(EXIT_SUCCESS); } int main() { pthread_t thread1, thread2, thread3, thread4; int thread1Num = 1; int thread2Num = 2; int thread3Num = 3; int thread4Num = 4; int thread1Create, thread2Create, thread3Create, thread4Create, i, temp; thread1Create = pthread_create(&thread1, NULL, (void *)thread_function, (char *)thread1Num); thread2Create = pthread_create(&thread2, NULL, (void *)thread_function, (char *)thread2Num); thread3Create = pthread_create(&thread3, NULL, (void *)thread_function, (char *)thread3Num); thread4Create = pthread_create(&thread4, NULL, (void *)thread_function, (char *)thread4Num); pthread_join(thread1, NULL); pthread_join(thread2, NULL); pthread_join(thread3, NULL); pthread_join(thread4, NULL); return 0; } </code></pre>

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