Method releaseSharedMemory

src/jrd/tpc.cpp:774–838

void TipCache::releaseSharedMemory(thread_db* tdbb, TraNumber oldest_old, TraNumber oldest_new)
{
	Database* dbb = tdbb->getDatabase();

	TpcBlockNumber lastInterestingBlockNumber = oldest_new / m_transactionsPerBlock;

	// If we didn't cross block boundary - there is nothing to do.
	// Note that due to the fuzziness of our caller's memory access to variables
	// there is an unlikely possibility that we might lose one such event.
	// This is not too bad, and next such event will clean things up.
	if (oldest_old / m_transactionsPerBlock == lastInterestingBlockNumber)
		return;

	// Populate array of blocks that might be unmapped and deleted.
	// We scan for blocks to clean up in descending order, but delete them in
	// ascending order to ensure for robust operation.
	PathName fileName;
	HalfStaticArray<TpcBlockNumber, 16> blocksToCleanup;

	for (TpcBlockNumber cleanupCounter = lastInterestingBlockNumber - SAFETY_GAP_BLOCKS;
		cleanupCounter; cleanupCounter--)
	{
		TpcBlockNumber blockNumber = cleanupCounter - 1;
		PathName fileName = StatusBlockData::makeSharedMemoryFileName(dbb, blockNumber, true);

		struct stat st;
		// If file is not found -- look no further
		if (stat(fileName.c_str(), &st) != 0)
			break;

		blocksToCleanup.add(blockNumber);
	}

	if (blocksToCleanup.isEmpty())
		return;

	SyncLockGuard sync(&m_sync_status, SYNC_EXCLUSIVE, FB_FUNCTION);
	while (blocksToCleanup.hasData())
	{
		TpcBlockNumber blockNumber = blocksToCleanup.pop();

		if (m_blocks_memory.locate(blockNumber))
		{
			StatusBlockData* block = m_blocks_memory.current();
			m_blocks_memory.fastRemove();
			delete block;
		}

		// Signal other processes to release resources
		Lock temp(tdbb, sizeof(TpcBlockNumber), LCK_tpc_block);
		temp.setKey(blockNumber);
		if (!LCK_lock(tdbb, &temp, LCK_EX, LCK_WAIT))
		{
			gds__log("TPC BUG: Unable to obtain cleanup lock for block %" UQUADFORMAT, blockNumber);
			fb_assert(false);
			break;
		}