void cleanupsems(void)
{
int s;
s = msemgrab(SEM0, 0);
if (s != -1)
{
msemrm(s);
}
}
/**
* Cleanup all ipc resources
*/
static void ipc_shutdown(void)
{
/* We need to block all signals to avoid race condition */
sigset_t blocked_signals;
(void) sigfillset(&blocked_signals);
(void) sigprocmask(SIG_BLOCK, &blocked_signals, NULL);
/* cleanup has already been done */
if(cleanup == 1) {
return;
}
cleanup = 1;
/* If cnd has already been aquired, try to remove it (would return -1 if cnd had already been removed by other process) */
if(cnd != -1) {
(void) msemrm(cnd);
}
/* detach SHM Segment (So it can be free'd later, or by other process) */
shm_detach();
if(mtx != -1) {
/* This fails with -1 if onother process has already done the cleanup of smh segment */
if(semdown(mtx) != -1) {
/*
* It might happen, that we only fail to aquire shm segment, but have a working mtx.
* In this case we will not destroy the mtx, because other processes might have created an shm segment and will therefor need a working mtx to free it.
*/
if(shm != -1) {
(void) shmctl(shm, IPC_RMID, NULL);
(void) semrm(mtx);
} else {
(void) semup(mtx);
}
}
}
}
int server(void)
{
int s = mseminit(SEM0, 0600, 2, 0, 1);
if (s == -1) {
perror("mseminit");
return 1;
}
int cnt = 1;
for (int i = 0; i < 5; ++i) {
if (mP(s, 1, 0) != 0) {
if (errno == EINTR) {
/* interrupted by syscall, try again */
continue;
}
perror("mP(0)");
break;
}
printf("s%d", cnt);
cnt += 2;
fflush(stdout);
if (mV(s, 1, 1) != 0) {
perror("mV(1)");
break;
}
}
/* clean up semaphores */
if (msemrm(s) != 0) {
perror("msemrm");
}
return 0;
}