C++ SetLatch函数代码示例

/*
 * Signal handler for SIGHUP
 *
 * Used only in BufferSaver. Set a flag to notify the main loop of the signal
 * received, and set our latch to wake it up.
 */
static void
sighupHandler(SIGNAL_ARGS)
{
	got_sighup = true;
	if (MyProc)
		SetLatch(&MyProc->procLatch);
}

/*
 * Wake up (using latch) the specified logical replication worker.
 *
 * Caller must hold lock, else worker->proc could change under us.
 */
void
logicalrep_worker_wakeup_ptr(LogicalRepWorker *worker)
{
	Assert(LWLockHeldByMe(LogicalRepWorkerLock));

	SetLatch(&worker->proc->procLatch);
}

/*
 * ProcSendSignal - send a signal to a backend identified by PID
 */
void
ProcSendSignal(int pid)
{
	PGPROC	   *proc = NULL;

	if (RecoveryInProgress())
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile PROC_HDR *procglobal = ProcGlobal;

		SpinLockAcquire(ProcStructLock);

		/*
		 * Check to see whether it is the Startup process we wish to signal.
		 * This call is made by the buffer manager when it wishes to wake up a
		 * process that has been waiting for a pin in so it can obtain a
		 * cleanup lock using LockBufferForCleanup(). Startup is not a normal
		 * backend, so BackendPidGetProc() will not return any pid at all. So
		 * we remember the information for this special case.
		 */
		if (pid == procglobal->startupProcPid)
			proc = procglobal->startupProc;

		SpinLockRelease(ProcStructLock);
	}

	if (proc == NULL)
		proc = BackendPidGetProc(pid);

	if (proc != NULL)
	{
		SetLatch(&proc->procLatch);
	}
}

/*
 * ProcWakeup -- wake up a process by releasing its private___ semaphore.
 *
 *	 Also remove the process from the wait queue and set its links invalid.
 *	 RETURN: the next process in the wait queue.
 *
 * The appropriate lock partition lock must be held by caller.
 *
 * XXX: presently, this code is only used for the "success" case, and only
 * works correctly for that case.  To clean up in failure case, would need
 * to twiddle the lock's request counts too --- see RemoveFromWaitQueue.
 * Hence, in practice the waitStatus parameter must be STATUS_OK.
 */
PGPROC *
ProcWakeup(PGPROC *proc, int waitStatus)
{
	PGPROC	   *retProc;

	/* Proc should be sleeping ... */
	if (proc->links.prev == NULL ||
		proc->links.next == NULL)
		return NULL;
	Assert(proc->waitStatus == STATUS_WAITING);

	/* Save next process before we zap the list link */
	retProc = (PGPROC *) proc->links.next;

	/* Remove process from wait queue */
	SHMQueueDelete(&(proc->links));
	(proc->waitLock->waitProcs.size)--;

	/* Clean up process' state and pass it the ok/fail signal */
	proc->waitLock = NULL;
	proc->waitProcLock = NULL;
	proc->waitStatus = waitStatus;

	/* And awaken it */
	SetLatch(&proc->procLatch);

	return retProc;
}

/* SIGUSR2: set flag to do a last cycle and shut down afterwards */
static void
WalSndLastCycleHandler(SIGNAL_ARGS)
{
	ready_to_stop = true;
	if (MyWalSnd)
		SetLatch(&MyWalSnd->latch);
}

static void
worker_spi_sighup(SIGNAL_ARGS)
{
	elog(LOG, "got sighup");
	if (MyProc)
		SetLatch(&MyProc->procLatch);
}

/* SIGHUP: set flag to re-read config file at next convenient time */
static void
WalSndSigHupHandler(SIGNAL_ARGS)
{
	got_SIGHUP = true;
	if (MyWalSnd)
		SetLatch(&MyWalSnd->latch);
}

/* SIGTERM: set flag to shut down */
static void
WalSndShutdownHandler(SIGNAL_ARGS)
{
	shutdown_requested = true;
	if (MyWalSnd)
		SetLatch(&MyWalSnd->latch);
}

/*
 * Signal handler for SIGHUP
 *		Set a flag to let the main loop to reread the config file, and set
 *		our latch to wake it up.
 */
static void
pg_keeper_sighup(SIGNAL_ARGS)
{
	got_sighup = true;
	if (MyProc)
		SetLatch(&MyProc->procLatch);
}

static void
IdleInTransactionSessionTimeoutHandler(void)
{
	IdleInTransactionSessionTimeoutPending = true;
	InterruptPending = true;
	SetLatch(MyLatch);
}

static void
terminate_group(ContQueryProcGroup *grp)
{
	bool found;
	int i;

	grp->active = true;

	for (i = 0; i < TOTAL_SLOTS; i++)
	{
		ContQueryProc *proc = &grp->procs[i];

		/* Wake up processes, so they can see the terminate flag. */
		SetLatch(proc->latch);

		/* Let workers crash now as well in case we force terminate them. */
		ChangeBackgroundWorkerRestartState(&proc->handle, true, 0);
	}

	/* Wait for a bit and then force terminate any processes that are still alive. */
	pg_usleep(Max(ContQuerySchedulerShmem->params.max_wait, MIN_WAIT_TERMINATE_MS) * 1000);

	for (i = 0; i < TOTAL_SLOTS; i++)
	{
		ContQueryProc *proc = &grp->procs[i];
		TerminateBackgroundWorker(&proc->handle);
	}

	hash_search(ContQuerySchedulerShmem->proc_table, &grp->db_oid, HASH_REMOVE, &found);

	Assert(found);

	TupleBufferDrain(WorkerTupleBuffer, grp->db_oid);
	TupleBufferDrain(CombinerTupleBuffer, grp->db_oid);
}

/* SIGHUP signal handler for archiver process */
static void
ArchSigHupHandler(SIGNAL_ARGS)
{
	/* set flag to re-read config file at next convenient time */
	got_SIGHUP = true;
	/* let the waiting loop iterate */
	SetLatch(&mainloop_latch);
}

static void
hello_sighup(SIGNAL_ARGS)
{
	int save_errno = errno;
	got_sighup = true;
	SetLatch(MyLatch);
	errno = save_errno;
}

/* SIGUSR1 signal handler for archiver process */
static void
pgarch_waken(SIGNAL_ARGS)
{
	/* set flag that there is work to be done */
	wakened = true;
	/* let the waiting loop iterate */
	SetLatch(&mainloop_latch);
}

/* Wake up all walsenders */
void
WalSndWakeup(void)
{
	int			i;

	for (i = 0; i < max_wal_senders; i++)
		SetLatch(&WalSndCtl->walsnds[i].latch);
}