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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#include <assert.h>
struct thread_data {
pthread_t thrd;
int id;
int result;
};
#define NTHREADS 8
static const unsigned int nthreads = NTHREADS;
static const unsigned int iterations = 4000;
static struct thread_data thrds[NTHREADS];
/* r/w by threads */
static int sum = 0;
void *
thread_func(void *arg)
{
int i;
int s;
struct thread_data *td = (struct thread_data *) arg;
printf("Thread %d started ..\n", td->id);
/* critical section - no sync */
s = sum; // READ
for (i = 0; i < iterations; i++) {
s++;
}
sum = s; // WRITE
return NULL;
}
int
main(int argc, char *argv[])
{
int i;
for (i = 0; i < nthreads; i++) {
thrds[i].id = i;
thrds[i].result = 0;
assert( pthread_create( &(thrds[i].thrd), NULL, thread_func, (void*)&thrds[i] ) == 0 );
}
for (i = 0; i < nthreads; i++) {
assert( pthread_join(thrds[i].thrd, NULL) == 0 );
}
printf("Expected result: sum == %d\n", iterations*nthreads);
if (sum == iterations*nthreads) {
printf("It worked randomly, lucky dude ..\n");
} else {
printf("This should be the common occasion: sum == %d\n", sum);
}
return 0;
}
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