From: Chris Friesen <cfriesen@nortelnetworks.com>
To: David Schwartz <davids@webmaster.com>
Cc: MarKol <markol4@wp.pl>, linux-kernel@vger.kernel.org
Subject: Re: select for UNIX sockets?
Date: Sun, 08 Jun 2003 00:15:52 -0400 [thread overview]
Message-ID: <3EE2B878.6050809@nortelnetworks.com> (raw)
In-Reply-To: MDEHLPKNGKAHNMBLJOLKMEOBDHAA.davids@webmaster.com
David Schwartz wrote:
> You are doing something wrong. You are using 'select' along with blocking
> I/O operations. You can't make bricks without clay. If you don't want to
> block, you must use non-blocking socket operations. End of story.
That's funny, I was under the impression that the whole point of using select()
was to enable the use of blocking I/O. If you are on a uniprocessor system, in
a single thread, and select() says that a socket is writeable, then I had darn
well better be able to write to that socket!
Sure, this gets more complicated when multiprocessing or multithreading, but the
test program does neither of these.
> Just because 'select' indicates a write hit, you are not assured that some
> particular write at a later time will not block. Past performance does not
> guarantee future results.
Think about the whole reason for select()'s existance. If a single-threaded app
calls select() and is told a socket is writeable, then a write to that socket
should either immediately succeed or immediately fail (if the other socket
disappeared in between the calls, for instance).
Now granted I use non-blocking I/O out of paranoia, but even there if select()
says it is writeable and the send call returns EAGAIN then we get into a nice
little infinite loop.
select() should be reliable.
Chris
--
Chris Friesen | MailStop: 043/33/F10
Nortel Networks | work: (613) 765-0557
3500 Carling Avenue | fax: (613) 765-2986
Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com
next prev parent reply other threads:[~2003-06-08 4:02 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-06 12:20 select for UNIX sockets? MarKol
2003-06-07 0:14 ` David Schwartz
2003-06-08 0:04 ` Krzysztof Halasa
2003-06-09 3:11 ` David Schwartz
2003-06-09 17:18 ` Krzysztof Halasa
2003-06-09 17:55 ` David Schwartz
2003-06-09 22:24 ` Krzysztof Halasa
2003-06-10 13:34 ` Timothy Miller
2003-06-10 13:52 ` Richard B. Johnson
2003-06-10 14:21 ` Krzysztof Halasa
2003-06-10 19:04 ` Jesse Pollard
2003-06-11 21:55 ` Krzysztof Halasa
2003-06-11 22:50 ` David Schwartz
2003-06-11 12:51 ` Edgar Toernig
2003-06-10 21:40 ` David Schwartz
2003-06-11 22:04 ` Krzysztof Halasa
2003-06-09 23:45 ` James Stevenson
2003-06-08 4:15 ` Chris Friesen [this message]
2003-06-09 3:05 ` David Schwartz
2003-06-09 16:46 ` MarKol
2003-06-09 17:05 ` David Schwartz
-- strict thread matches above, loose matches on Subject: below --
2003-06-04 12:19 Petr Vandrovec
2003-06-06 0:28 ` Valdis.Kletnieks
2003-06-06 0:38 ` Petr Vandrovec
2003-06-03 0:08 Krzysztof Halasa
2003-06-03 14:51 ` Alan Cox
2003-06-04 23:27 ` Krzysztof Halasa
2003-06-05 13:17 ` Krzysztof Halasa
2003-06-04 11:55 ` Jesse Pollard
2003-06-04 12:42 ` Krzysztof Halasa
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3EE2B878.6050809@nortelnetworks.com \
--to=cfriesen@nortelnetworks.com \
--cc=davids@webmaster.com \
--cc=linux-kernel@vger.kernel.org \
--cc=markol4@wp.pl \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).