From: Junio C Hamano <gitster@pobox.com>
To: Stefan Beller <sbeller@google.com>
Cc: git@vger.kernel.org, jacob.keller@gmail.com, peff@peff.net,
jrnieder@gmail.com, johannes.schindelin@gmail.com,
Jens.Lehmann@web.de, vlovich@gmail.com
Subject: Re: [PATCHv3 02/13] xread: poll on non blocking fds
Date: Mon, 21 Sep 2015 16:55:34 -0700 [thread overview]
Message-ID: <xmqq37y78gzt.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <1442875159-13027-3-git-send-email-sbeller@google.com> (Stefan Beller's message of "Mon, 21 Sep 2015 15:39:08 -0700")
Stefan Beller <sbeller@google.com> writes:
> So if we get an EAGAIN or EWOULDBLOCK error the fd must be nonblocking.
> As the intend of xread is to read as much as possible either until the
> fd is EOF or an actual error occurs, we can ease the feeder of the fd
> by not spinning the whole time, but rather wait for it politely by not
> busy waiting.
As you said in the cover letter, this does look questionable. It is
sweeping the problem under the rug (the hard-coded 100ms is a good
clue to tell that). If the caller does want us to read thru to the
end, then we would need to make it easier for such a caller to stop
marking the file descriptor to be non-blocking, but this does not do
anything to help that. An alternative might be to automatically
turn nonblocking off temporarily once we get EAGAIN (and turn it on
again before leaving); that would be an approach to make it
unnecessary to fix the caller (which has its own set of problems,
though).
> + if (i < 0) {
> + if (errno == EINTR || errno == ENOMEM)
> + continue;
I can sort of see EINTR but why is ENOMEM any special than other
errors?
> + else
> + die_errno("poll");
> + }
> + }
> + }
> return nr;
> }
> }
next prev parent reply other threads:[~2015-09-21 23:55 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-21 22:39 [PATCHv3 00/13] fetch submodules in parallel and a preview on parallel "submodule update" Stefan Beller
2015-09-21 22:39 ` [PATCHv3 01/13] Sending "Fetching submodule <foo>" output to stderr Stefan Beller
2015-09-21 23:47 ` Junio C Hamano
2015-09-21 22:39 ` [PATCHv3 02/13] xread: poll on non blocking fds Stefan Beller
2015-09-21 23:55 ` Junio C Hamano [this message]
2015-09-22 4:55 ` Torsten Bögershausen
2015-09-22 6:23 ` Jacob Keller
2015-09-22 18:40 ` Torsten Bögershausen
2015-09-22 19:45 ` Junio C Hamano
2015-09-22 19:49 ` Jeff King
2015-09-22 20:00 ` Junio C Hamano
2015-09-23 0:14 ` Stefan Beller
2015-09-23 0:43 ` Junio C Hamano
2015-09-23 1:51 ` Jeff King
2015-09-21 23:56 ` Eric Sunshine
2015-09-22 15:58 ` Junio C Hamano
2015-09-22 17:38 ` Stefan Beller
2015-09-22 18:21 ` Junio C Hamano
2015-09-22 18:41 ` Stefan Beller
2015-09-21 22:39 ` [PATCHv3 03/13] xread_nonblock: add functionality to read from fds nonblockingly Stefan Beller
2015-09-22 0:02 ` Junio C Hamano
2015-09-22 0:10 ` Junio C Hamano
2015-09-22 6:26 ` Jacob Keller
2015-09-22 6:27 ` Jacob Keller
2015-09-22 15:59 ` Junio C Hamano
2015-09-21 22:39 ` [PATCHv3 04/13] strbuf: add strbuf_read_once to read without blocking Stefan Beller
2015-09-22 0:17 ` Junio C Hamano
2015-09-22 6:29 ` Jacob Keller
2015-09-21 22:39 ` [PATCHv3 05/13] run-command: factor out return value computation Stefan Beller
2015-09-22 0:38 ` Junio C Hamano
2015-09-21 22:39 ` [PATCHv3 06/13] run-command: add an asynchronous parallel child processor Stefan Beller
2015-09-22 1:08 ` Junio C Hamano
2015-09-22 18:28 ` Stefan Beller
2015-09-22 19:53 ` Junio C Hamano
2015-09-22 21:31 ` Stefan Beller
2015-09-22 21:41 ` Junio C Hamano
2015-09-22 21:54 ` Stefan Beller
2015-09-22 22:23 ` Junio C Hamano
2015-09-21 22:39 ` [PATCHv3 07/13] fetch_populated_submodules: use new parallel job processing Stefan Beller
2015-09-22 16:28 ` Junio C Hamano
2015-09-21 22:39 ` [PATCHv3 08/13] submodules: allow parallel fetching, add tests and documentation Stefan Beller
2015-09-21 22:39 ` [PATCHv3 09/13] submodule config: keep update strategy around Stefan Beller
2015-09-22 0:56 ` Eric Sunshine
2015-09-22 15:50 ` Stefan Beller
2015-09-21 22:39 ` [PATCHv3 10/13] git submodule update: cmd_update_recursive Stefan Beller
2015-09-21 22:39 ` [PATCHv3 11/13] git submodule update: cmd_update_clone Stefan Beller
2015-09-21 22:39 ` [PATCHv3 12/13] git submodule update: cmd_update_fetch Stefan Beller
2015-09-21 22:39 ` [PATCHv3 13/13] Rewrite submodule update in C Stefan Beller
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