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/*
* Test whether all data races are detected in a multithreaded program with
* user-annotated barriers. See also pth_barrier.c.
*/
#define _GNU_SOURCE
#include <pthread.h> /* pthread_create() */
#include <stdio.h> /* fprintf() */
#include <stdlib.h> /* atoi() */
#include <string.h> /* memset() */
#include <unistd.h> /* usleep() */
#include "../../drd/drd.h"
#include "../../config.h"
#define BARRIER_SERIAL_THREAD -1
/* Local datatypes. */
typedef struct
{
/*
* number of threads that must call barrier_wait() before any of them
* successfully return from the call.
*/
unsigned thread_count;
/* number of barrier_wait() calls since last barrier. */
volatile unsigned wait_count;
/*
* barrier count. Only the least significant bit matters -- a single bit
* counter would be sufficient.
*/
volatile unsigned barrier_count;
} barrier_t;
struct threadinfo
{
int thread_num;
barrier_t* b;
pthread_t tid;
int* array;
int iterations;
};
/* Local variables. */
static int s_silent;
/* Local functions. */
static void barrier_init(barrier_t* b, unsigned count)
{
b->thread_count = count;
b->wait_count = 0;
b->barrier_count = 0;
ANNOTATE_BARRIER_INIT(b, count, 0);
}
static void barrier_destroy(barrier_t* b)
{
ANNOTATE_BARRIER_DESTROY(b);
memset(b, 0, sizeof(*b));
}
static int barrier_wait(barrier_t* b)
{
int res;
unsigned barrier_count;
res = 0;
ANNOTATE_BARRIER_WAIT_BEFORE(b);
barrier_count = b->barrier_count;
if (__sync_add_and_fetch(&b->wait_count, 1) == b->thread_count)
{
__sync_sub_and_fetch(&b->wait_count, b->thread_count);
__sync_add_and_fetch(&b->barrier_count, 1);
res = BARRIER_SERIAL_THREAD;
}
else
{
while (b->barrier_count == barrier_count)
{
#ifndef HAVE_PTHREAD_YIELD
/* Darwin doesn't have an implementation of pthread_yield(). */
usleep(100 * 1000);
#else
pthread_yield();
#endif
}
}
ANNOTATE_BARRIER_WAIT_AFTER(b);
return res;
}
/*
* Single thread, which touches p->iterations elements of array p->array.
* Each modification of an element of p->array is a data race.
*/
static void* threadfunc(struct threadinfo* p)
{
int i;
int* const array = p->array;
barrier_t* const b = p->b;
if (! s_silent)
printf("thread %d iteration 0\n", p->thread_num);
barrier_wait(b);
for (i = 0; i < p->iterations; i++)
{
if (! s_silent)
printf("thread %d iteration %d; writing to %p\n",
p->thread_num, i + 1, &array[i]);
array[i] = i;
barrier_wait(b);
}
return 0;
}
/* Actual test, consisting of nthread threads. */
static void barriers_and_races(const int nthread, const int iterations)
{
const struct timespec delay = { 0, 100 * 1000 * 1000 };
int i;
struct threadinfo* t;
barrier_t b;
int* array;
t = malloc(nthread * sizeof(struct threadinfo));
array = malloc(iterations * sizeof(array[0]));
if (! s_silent)
printf("&array[0] = %p\n", array);
barrier_init(&b, nthread);
for (i = 0; i < nthread; i++)
{
t[i].thread_num = i + 1;
t[i].b = &b;
t[i].array = array;
t[i].iterations = iterations;
pthread_create(&t[i].tid, 0, (void*(*)(void*))threadfunc, &t[i]);
nanosleep(&delay, 0);
}
for (i = 0; i < nthread; i++)
pthread_join(t[i].tid, 0);
barrier_destroy(&b);
free(array);
free(t);
}
int main(int argc, char** argv)
{
int nthread;
int iterations;
nthread = (argc > 1) ? atoi(argv[1]) : 2;
iterations = (argc > 2) ? atoi(argv[2]) : 3;
s_silent = (argc > 3) ? atoi(argv[3]) : 0;
barriers_and_races(nthread, iterations);
fprintf(stderr, "Done.\n");
return 0;
}
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