/* * Demonstrate cygserver hang under concurrent sysv semaphore traffic. Run * without arguments. Output will cease within a few seconds, and cygserver * will be unresponsive to all clients. * * This is compatible with default cygserver settings; it uses a single * semaphore set of four semaphores. */ #include #include #include #include #include #include #include #include #define SEM_KEY 0x631a2c3e #define N_CYCLE 1000000 union semun { int val; struct semid_ds *buf; unsigned short *array; }; static int print_every = 1; /* In parallel, N_WORKER processes run this function. */ static int do_worker(int ordinal, int set, int N_SEMA) { int i; struct sembuf op; printf("start worker %d\n", ordinal); fflush(stdout); op.sem_flg = 0; for (i = 1; i <= N_CYCLE; i++) { op.sem_num = random() % N_SEMA; op.sem_op = -1; if (0 > semop(set, &op, 1)) { perror("semop"); return 1; } op.sem_op = 1; if (0 > semop(set, &op, 1)) { perror("semop"); return 1; } if (i % print_every == 0) { printf("worker %d: %d cycles elapsed\n", ordinal, i); fflush(stdout); } } return 0; } int main(int argc, char **argv) { int status = 1, set, i, child_status; int N_WORKER, N_SEMA; switch(argc){ case 3: print_every = atoi(argv[2]); case 2: N_WORKER=atoi(argv[1]); N_SEMA= (N_WORKER/4); break; default: fprintf(stderr, "Usage: sema_parallel workers [print-every-N]\n"); return status; } puts("semget"); fflush(stdout); set = semget(SEM_KEY, N_SEMA, IPC_CREAT | 0600); if (set == -1) { perror("semget"); return status; } puts("SETVAL"); fflush(stdout); for (i = 0; i < N_SEMA; i++) { union semun s; s.val = 1; if (0 > semctl(set, i, SETVAL, s)) { perror("semctl(SETVAL)"); goto cleanup; } } for (i = 0; i < N_WORKER; i++) { pid_t pid; pid = fork(); switch (pid) { case -1: perror("fork"); goto cleanup; case 0: return do_worker(i, set, N_SEMA ); } } status = 0; cleanup: while (wait(&child_status) != -1) ; if (errno != ECHILD) { perror("wait"); status = 1; } if (0 > semctl(set, 0, IPC_RMID)) { perror("semtctl(IPC_RMID)"); status = 1; } return status; }