From: Johannes Sixt <j6t@kdbg.org>
Date: Tue, 03 Nov 2015 21:03:02 GMT
Subject: Re: git.git as of tonight
Message-ID: <56392106.1010401@kdbg.org>
In-Reply-To: <CAGZ79kbAj-tZS3X1EwFw_gGh1=YU8M0OmEX91W8f++fqs6TiBA@mail.gmail.com>

Am 03.11.2015 um 19:18 schrieb Stefan Beller:
> ... ReadFileEx ... "overlapped" operation.

Let's not go there just yet.

>>   1. Make this an optional feature so that platforms can compile it
>>      out, if it is not already done.  My preference, even if we go
>>      that route, would be to see if we can find a way to preserve the
>>      overall code structure (e.g. instead of spawning multiple
>>      workers, which is why the code needs NONBLOCK to avoid getting
>>      stuck on reading from one while others are working, perhaps we
>>      can spawn only one and not do a nonblock read?).
>
> Yeah that would be my understanding as well. If we don't come up with
> a good solution for parallelism in Windows now, we'd need to make it at
> least working in the jobs=1 case as well as it worked before.

That should be possible. I discovered today that we have this function:

static void set_nonblocking(int fd)
{
	int flags = fcntl(fd, F_GETFL);
	if (flags < 0)
		warning("Could not get file status flags, "
			"output will be degraded");
	else if (fcntl(fd, F_SETFL, flags | O_NONBLOCK))
		warning("Could not set file status flags, "
			"output will be degraded");
}

Notice that it is not a fatal condition if O_NONBLOCK cannot be 
established. (BTW, did you ever test this condition?) If we add two 
lines (which remove the stuff that does not work on Windows) like this:

static void set_nonblocking(int fd)
{
#ifndef GIT_WINDOWS_NATIVE
	int flags = fcntl(fd, F_GETFL);
	if (flags < 0)
		warning("Could not get file status flags, "
			"output will be degraded");
	else if (fcntl(fd, F_SETFL, flags | O_NONBLOCK))
#endif
		warning("Could not set file status flags, "
			"output will be degraded");
}

we should get something that works, theoretically. We still need a more 
complete waitpid emulation, but that does not look like rocket science. 
I'll investigate further in this direction.

-- Hannes