void my_lock(int fd)
{
int oflag, i;
union semun arg;
struct semid_ds seminfo;
if (initflag == 0) {
oflag = IPC_CREAT | IPC_EXCL | SVSEM_MODE;
if ((semid = semget(Ftok(LOCK_PATH, 0), 1, oflag)) >= 0) {
arg.val = 1;
Semctl(semid, 0, SETVAL, arg);
} else if (errno == EEXIST) {
semid = Semget(Ftok(LOCK_PATH, 0), 1, SVSEM_MODE);
arg.buf = &seminfo;
for (i = 0; i < MAX_TRIES; i++) {
Semctl(semid, 0, IPC_STAT, arg);
if (arg.buf->sem_otime != 0)
goto init;
sleep(1);
}
err_quit("semget OK, but semaphore not initalized");
} else
err_sys("semget error");
init:
initflag = 1;
postop.sem_num = 0;
postop.sem_op = 1;
postop.sem_flg = SEM_UNDO;
waitop.semnum = 0;
waitop.semop = -1;
waitop.semflg = SEM_UNDO;
}
Semop(semid, &waitop, 1);
}
int
main(int argc, char **argv)
{
int i, nthreads;
pthread_t tid[MAXNTHREADS];
union semun arg;
if (argc != 3)
err_quit("usage: incr_svsem2 <#loops> <#threads>");
nloop = atoi(argv[1]);
nthreads = min(atoi(argv[2]), MAXNTHREADS);
/* 4create semaphore and initialize to 0 */
shared.semid = Semget(IPC_PRIVATE, 1, IPC_CREAT | SVSEM_MODE);
arg.val = 0;
Semctl(shared.semid, 0, SETVAL, arg);
postop.sem_num = 0; /* and init the two semop() structures */
postop.sem_op = 1;
postop.sem_flg = SEM_UNDO;
waitop.sem_num = 0;
waitop.sem_op = -1;
waitop.sem_flg = SEM_UNDO;
/* 4create all the threads */
Set_concurrency(nthreads);
for (i = 0; i < nthreads; i++) {
Pthread_create(&tid[i], NULL, incr, NULL);
}
/* 4start the timer and release the semaphore */
Start_time();
Semop(shared.semid, &postop, 1); /* up by 1 */
/* 4wait for all the threads */
for (i = 0; i < nthreads; i++) {
Pthread_join(tid[i], NULL);
}
printf("microseconds: %.0f usec\n", Stop_time());
if (shared.counter != nloop * nthreads)
printf("error: counter = %ld\n", shared.counter);
Semctl(shared.semid, 0, IPC_RMID);
exit(0);
}
void
my_lock(int fd)
{
int oflag, i;
union semun arg;
struct semid_ds seminfo;
if (initflag == 0) {
oflag = IPC_CREAT | IPC_EXCL | SVSEM_MODE;
if ( (semid = semget(Ftok(LOCK_PATH, 0), 1, oflag)) >= 0) {
/* 4success, we're the first so initialize */
arg.val = 1;
Semctl(semid, 0, SETVAL, arg);
} else if (errno == EEXIST) {
/* 4someone else has created; make sure it's initialized */
semid = Semget(Ftok(LOCK_PATH, 0), 1, SVSEM_MODE);
arg.buf = &seminfo;
for (i = 0; i < MAX_TRIES; i++) {
Semctl(semid, 0, IPC_STAT, arg);
if (arg.buf->sem_otime != 0)
goto init;
Write(pipefd[1], "", 1); /* tell parent */
sleep(1);
}
err_quit("semget OK, but semaphore not initialized");
} else
err_sys("semget error");
init:
initflag = 1;
postop.sem_num = 0; /* and init the two semop() structures */
postop.sem_op = 1;
postop.sem_flg = SEM_UNDO;
waitop.sem_num = 0;
waitop.sem_op = -1;
waitop.sem_flg = SEM_UNDO;
}
Semop(semid, &waitop, 1); /* down by 1 */
}
int main(int argc, char **argv)
{
int semid, nsems, i;
struct semid_ds seminfo;
unsigned short *ptr;
union semun arg;
if (argc < 2)
err_quit("Usage: setvalue <pathname> [ value ...]");
//first get the number of semaphore in the set
semid = Semget(Ftok(argv[1], 0), 0, 0);
arg.buf = &seminfo;
Semctl(semid, 0, IPC_STAT, arg);
nsems = arg.buf->sem_nsems;
//now get the values from the command line
ptr = Calloc(nsems, sizeof(unsigned short));
arg.array = ptr;
for (i = 0; i < nsems; i++)
ptr[i] = atoi(argv[i + 2]);
Semctl(semid, 0, SETALL, arg);
exit(0);
}
