Function pipeThread

src/backend/postmaster/syslogger.c:1788–1854

* Worker thread to transfer data from the pipe to the current logfile. * * We need this because on Windows, WaitForMultipleObjects does not work on * unnamed pipes: it always reports "signaled", so the blocking ReadFile won't * allow for SIGHUP; and select is for sockets only. */

 * allow for SIGHUP; and select is for sockets only.
 */
static unsigned int __stdcall
pipeThread(void *arg)
{
	char		logbuffer[READ_BUF_SIZE];
	int			bytes_in_logbuffer = 0;

	for (;;)
	{
		DWORD		bytesRead;
		BOOL		result;

		result = ReadFile(syslogPipe[0],
						  logbuffer + bytes_in_logbuffer,
						  sizeof(logbuffer) - bytes_in_logbuffer,
						  &bytesRead, 0);

		/*
		 * Enter critical section before doing anything that might touch
		 * global state shared by the main thread. Anything that uses
		 * palloc()/pfree() in particular are not safe outside the critical
		 * section.
		 */
		EnterCriticalSection(&sysloggerSection);
		if (result)
		{
			DWORD		error = GetLastError();

			if (error == ERROR_HANDLE_EOF ||
				error == ERROR_BROKEN_PIPE)
				break;
			_dosmaperr(error);
			ereport(LOG,
					(errcode_for_file_access(),
					 errmsg("could not read from logger pipe: %m")));
		}
		else if (bytesRead > 0)
		{
			bytes_in_logbuffer += bytesRead;
			process_pipe_input(logbuffer, &bytes_in_logbuffer);
		}

		/*
		 * If we've filled the current logfile, nudge the main thread to do a
		 * log rotation.
		 */
		if (Log_RotationSize > 0)
		{
			if (ftell(syslogFile) >= Log_RotationSize * 1024L ||
				(csvlogFile != NULL && ftell(csvlogFile) >= Log_RotationSize * 1024L))
				SetLatch(MyLatch);
		}
		LeaveCriticalSection(&sysloggerSection);
	}

	/* We exit the above loop only upon detecting pipe EOF */
	pipe_eof_seen = true;

	/* if there's any data left then force it out now */