Function CCH_exclusive_attachment

src/jrd/cch.cpp:533–657

bool CCH_exclusive_attachment(thread_db* tdbb, USHORT level, SSHORT wait_flag, Sync* exGuard)
{
/**************************************
 *
 *	C C H _ e x c l u s i v e _ a t t a c h m e n t
 *
 **************************************
 *
 * Functional description
 *	Get exclusive access to a database. If we get it, return true.
 *	If the wait flag is FALSE, and we can't get it, give up and
 *	return false.
 *
 **************************************/
	const int CCH_EXCLUSIVE_RETRY_INTERVAL = 10;	// retry interval in millseconds

	SET_TDBB(tdbb);
	Database* const dbb = tdbb->getDatabase();

	Sync dsGuard(&dbb->dbb_sync, FB_FUNCTION);

	const bool exLock = dbb->dbb_sync.ourExclusiveLock();
	if (!exLock)
		dsGuard.lock(level != LCK_none ? SYNC_EXCLUSIVE : SYNC_SHARED);
	else
		fb_assert(exGuard);

	Jrd::Attachment* const attachment = tdbb->getAttachment();

	if (attachment->att_flags & ATT_exclusive)
		return true;

	attachment->att_flags |= (level == LCK_none) ? ATT_attach_pending : ATT_exclusive_pending;

	const SLONG timeout = (wait_flag == LCK_WAIT) ? 1L << 30 : (-wait_flag * 1000 / CCH_EXCLUSIVE_RETRY_INTERVAL);

	// If requesting exclusive database access, then re-position attachment as the
	// youngest so that pending attachments may pass.

	if (level != LCK_none)
	{
		for (Jrd::Attachment** ptr = &dbb->dbb_attachments; *ptr; ptr = &(*ptr)->att_next)
		{
			if (*ptr == attachment)
			{
				*ptr = attachment->att_next;
				break;
			}
		}
		attachment->att_next = dbb->dbb_attachments;
		dbb->dbb_attachments = attachment;

		if (!exLock)
			dsGuard.downgrade(SYNC_SHARED);
	}

	for (SLONG remaining = timeout; remaining >= 0; remaining -= CCH_EXCLUSIVE_RETRY_INTERVAL)
	{