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#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mut1 = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mut2 = PTHREAD_MUTEX_INITIALIZER;
static bool last_round;
static int ntogo;
static bool alldone;
static void *
cons (void *arg)
{
pthread_mutex_lock (&mut1);
do
{
if (--ntogo == 0)
{
pthread_mutex_lock (&mut2);
alldone = true;
pthread_cond_signal (&cond2);
pthread_mutex_unlock (&mut2);
}
pthread_cond_wait (&cond1, &mut1);
}
while (! last_round);
pthread_mutex_unlock (&mut1);
return NULL;
}
int
main (int argc, char *argv[])
{
int opt;
int err;
int nthreads = 10;
int nrounds = 100;
bool keeplock = false;
while ((opt = getopt (argc, argv, "n:r:k")) != -1)
switch (opt)
{
case 'n':
nthreads = atol (optarg);
break;
case 'r':
nrounds = atol (optarg);
break;
case 'k':
keeplock = true;
break;
}
ntogo = nthreads;
pthread_t th[nthreads];
int i;
for (i = 0; i < nthreads; ++i)
if (__builtin_expect ((err = pthread_create (&th[i], NULL, cons, (void *) (long) i)) != 0, 0))
printf ("pthread_create: %s\n", strerror (err));
for (i = 0; i < nrounds; ++i)
{
pthread_mutex_lock (&mut2);
while (! alldone)
pthread_cond_wait (&cond2, &mut2);
pthread_mutex_unlock (&mut2);
pthread_mutex_lock (&mut1);
if (! keeplock)
pthread_mutex_unlock (&mut1);
ntogo = nthreads;
alldone = false;
if (i + 1 >= nrounds)
last_round = true;
pthread_cond_broadcast (&cond1);
if (keeplock)
pthread_mutex_unlock (&mut1);
}
for (i = 0; i < nthreads; ++i)
if ((err = pthread_join (th[i], NULL)) != 0)
printf ("pthread_create: %s\n", strerror (err));
return 0;
}
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