68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/*
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* This program ends up in a threadrace when the argument is around 1M
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*
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* We need synchronization primitives to help here!
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*/
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#include <pthread.h>
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#include <stdio.h>
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#include <stdlib.h>
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struct args {
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int max;
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char letter;
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pthread_mutex_t* mutex;
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};
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volatile int counter = 0;
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void* count_thread(void* arg) {
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struct args* a = arg;
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for (int i = 0; i < a->max; i++) {
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pthread_mutex_lock(a->mutex);
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counter = counter + 1;
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pthread_mutex_unlock(a->mutex);
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}
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// // But given this process is pretty fast... this is better
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// pthread_mutex_lock(a->mutex);
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// for (int i = 0; i < a->max; i++) {
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// counter = counter + 1;
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// }
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// pthread_mutex_unlock(a->mutex);
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printf("Thread %c: done with counter at %d\n", a->letter, counter);
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return NULL;
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}
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void* make_args(int max, char letter, pthread_mutex_t* mutex) {
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struct args* a = malloc(sizeof(struct args));
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a->max = max;
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a->letter = letter;
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a->mutex = mutex;
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return (void*) a;
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}
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int main(int argc, char* argv[]) {
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if (argc != 2) {
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exit(1);
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}
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int max = atoi(argv[1]);
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pthread_mutex_t* mutex = malloc(sizeof(pthread_mutex_t));
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pthread_mutex_init(mutex, NULL);
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pthread_t p1, p2;
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pthread_create(&p1, NULL, count_thread, make_args(max, 'A', mutex));
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pthread_create(&p2, NULL, count_thread, make_args(max, 'B', mutex));
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pthread_join(p1, NULL);
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pthread_join(p2, NULL);
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pthread_mutex_destroy(mutex);
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printf("main: done\n [counter: %d]\n [should: %d]\n", counter, max * 2);
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return 0;
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}
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