Re: [PATCH v3] mingw: workaround for hangs when sending STDIN

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Junio & Alex,

On Tue, 18 Feb 2020, Junio C Hamano wrote:

> "Alexandr Miloslavskiy via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
>
> > From: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
> >
> > Explanation
> > -----------
> > The problem here is flawed `poll()` implementation. When it tries to
> > see if pipe can be written without blocking, it eventually calls
> > `NtQueryInformationFile()` and tests `WriteQuotaAvailable`. However,
> > the meaning of quota was misunderstood. The value of quota is reduced
> > when either some data was written to a pipe, *or* there is a pending
> > read on the pipe. Therefore, if there is a pending read of size >= then

I usually try to refrain from grammar policing, but in this case, the typo
"then" (instead of "than") threw me.

Other than that, I think the patch is fine. At least it works as
advertised in my hands.

Thanks,
Dscho

> > the pipe's buffer size, poll() will think that pipe is not writable and
> > will hang forever, usually that means deadlocking both pipe users.
> > ...
> > Chosen solution
> > ---------------
> > Make `poll()` always reply "writable" for write end of the pipe.
> > Hopefully one day someone will find a way to implement it properly.
> >
> > Reproduction
> > ------------
> > printf "%8388608s" X >large_file.txt
> > git stash push --include-untracked -- large_file.txt
> >
> > I have decided not to include this as test to avoid slowing down the
> > test suite. I don't expect the specific problem to come back, and
> > chances are that `git stash push` will be reworked to avoid sending the
> > entire patch via STDIN.
> >
> > Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
> > ---
>
> Thanks for a detailed description.
>
> I notice that we saw no comments from Windows experts for these
> three rounds.  Can somebody give an Ack (or nack) on it at least?
>
> I picked obvious "experts" in the output from
>
>     $ git shortlog --since=1.year --no-merges master compat/ming\* compat/win\*
>
> Thanks.
>