From: Junio C Hamano <gitster@pobox•com>
To: Johannes Sixt <j6t@kdbg•org>
Cc: Stefan Beller <sbeller@google•com>,
git@vger•kernel.org, peff@peff•net,
johannes.schindelin@gmail•com, Jens.Lehmann@web•de,
ericsunshine@gmail•com, tboegi@web•de
Subject: Re: [PATCH 1/2] run-command: Remove set_nonblocking
Date: Thu, 05 Nov 2015 12:50:33 -0800 [thread overview]
Message-ID: <xmqqa8qs5fxi.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <563BBBBC.7070807@kdbg.org> (Johannes Sixt's message of "Thu, 5 Nov 2015 21:27:40 +0100")
Johannes Sixt <j6t@kdbg•org> writes:
> Am 05.11.2015 um 19:17 schrieb Stefan Beller:
>> strbuf_read_once can also operate on blocking file descriptors if we are
>> sure they are ready. The poll (2) command however makes sure this is the
>> case.
>>
>> Reading the manual for poll (2), there may be spurious returns indicating
>> readiness but that is for network sockets only. Pipes should be unaffected.
>> By having this patch, we rely on the correctness of poll to return
>> only pipes ready to read.
>>
>> This fixes compilation in Windows.
>
> It certainly does (but I haven't tested, yet). But parallel processes
> will not work because we do not have a sufficiently complete waitpid
> emulation, yet. (waitpid(-1, ...) is not implemented.)
>
> However, I think that the infrastructure can be simplified even further
> to a level that we do not need additional emulation on Windows.
;-)
This is why I love this list (and in general not rushing any change
too early to 'next').
> Which makes me think: Other users of start_command/finish_command work
> such that they
>
> 1. request a pipe by setting .out = -1
> 2. start_command
> 3. read from .out until EOF
> 4. close .out
> 5. wait for the process with finish_command
>
> But the parallel_process infrastructure does not follow this pattern.
> It
>
> 1. requests a pipe by setting .err = -1
> 2. start_command
> 3. read from .err
> 4. wait for the process with waitpid
>
> (and forgets to close .err). EOF is not in the picture (but that is
> not essential).
Unrelated tangent. daemon is another one that uses start_command()
but does not use finish_command().
> I suggest to change this such that we read from the children until EOF,
> mark them to be at their end of life, and then wait for them using
> finish_command (assuming that a process that closes stdout and stderr
> will die very soon if it is not already dead).
Hmm, interesting. This does match the normal "spawn, interact and
wait" cycle for a single process much better.
next prev parent reply other threads:[~2015-11-05 20:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-05 18:17 [PATCH 0/2] Remove non-blocking fds from run-command Stefan Beller
2015-11-05 18:17 ` [PATCH 1/2] run-command: Remove set_nonblocking Stefan Beller
2015-11-05 18:45 ` Junio C Hamano
2015-11-05 19:22 ` Stefan Beller
2015-11-05 19:37 ` Junio C Hamano
2015-11-05 20:27 ` Johannes Sixt
2015-11-05 20:50 ` Junio C Hamano [this message]
2015-11-05 22:20 ` Stefan Beller
2015-11-06 5:51 ` Johannes Sixt
2015-11-06 19:00 ` Stefan Beller
2015-11-06 21:41 ` Johannes Sixt
2015-11-05 18:17 ` [PATCH 2/2] strbuf: Correct documentation for strbuf_read_once Stefan Beller
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