int
main(int argc, char **argv)
{
int fd = 0, stat, nconflicts;
long i, j, nproc;
sem_t *ptr;
pid_t pid;
ssize_t n;
if (argc != 2)
err_quit("usage: locksvsemrace1 <#processes>");
nproc = atol(argv[1]);
Pipe(pipefd);
ptr = My_shm(sizeof(sem_t)); /* create memory-based semaphore */
Sem_init(ptr, 1, 0);
for (j = 0; j < nproc; j++) {
if (Fork() == 0) {
/* 4child */
Sem_wait(ptr); /* wait for parent to start children */
for (i = 0; i < 10; i++) {
my_lock(fd); /* lock the file */
my_unlock(fd); /* unlock the file */
}
exit(0);
}
/* parent loops around, creating next child */
}
for (j = 0; j < nproc; j++)
Sem_post(ptr); /* start all the children */
/* now just wait for all the children to finish */
while ( (pid = waitpid(-1, &stat, WNOHANG)) > 0)
;
Close(pipefd[1]);
nconflicts = 0;
while ( (n = Read(pipefd[0], &stat, 1)) > 0)
nconflicts += n;
printf("%d conflicts\n", nconflicts);
exit(0);
}
int
main(int argc, char **argv)
{
int i, nprocs;
pid_t childpid[MAXNPROC];
if (argc != 3)
err_quit("usage: incr_rwlock5 <#loops> <#processes>");
nloop = atoi(argv[1]);
nprocs = min(atoi(argv[2]), MAXNPROC);
/* 4get shared memory for parent and children */
shared = My_shm(sizeof(struct shared));
/* 4initialize the read-write lock and obtain write lock */
Rwlock_init(&shared->rwlock, USYNC_PROCESS, NULL);
Rw_wrlock(&shared->rwlock);
/* 4create all the children */
for (i = 0; i < nprocs; i++) {
if ( (childpid[i] = Fork()) == 0) {
incr(NULL);
exit(0);
}
}
/* 4parent: start the timer and release the write lock */
Start_time();
Rw_unlock(&shared->rwlock);
/* 4wait for all the children */
for (i = 0; i < nprocs; i++) {
Waitpid(childpid[i], NULL, 0);
}
printf("microseconds: %.0f usec\n", Stop_time());
if (shared->counter != nloop * nprocs)
printf("error: counter = %ld\n", shared->counter);
exit(0);
}
int
main(int argc, char **argv)
{
int i, nprocs;
pid_t childpid[MAXNPROC];
if (argc != 3)
err_quit("usage: incr_pxsem9 <#loops> <#processes>");
nloop = atoi(argv[1]);
nprocs = min(atoi(argv[2]), MAXNPROC);
/* 4get shared memory for parent and children */
shared = My_shm(sizeof(struct shared));
/* 4initialize memory-based semaphore to 0 */
Sem_init(&mutex, 1, 0);
/* 4create all the children */
for (i = 0; i < nprocs; i++) {
if ( (childpid[i] = Fork()) == 0) {
incr(NULL);
exit(0);
}
}
/* 4parent: start the timer and release the semaphore */
Start_time();
Sem_post(&mutex);
/* 4wait for all the children */
for (i = 0; i < nprocs; i++) {
Waitpid(childpid[i], NULL, 0);
}
printf("microseconds: %.0f usec\n", Stop_time());
if (shared->counter != nloop * nprocs)
printf("error: counter = %ld\n", shared->counter);
exit(0);
}