From: Rainer Weikusat <rweikusat@mobileactivedefense•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: David Miller <davem@davemloft•net>,
David.Laight@ACULAB•COM, netdev@vger•kernel.org
Subject: Re: [PATCH] net: unix: non blocking recvmsg() should not return -EINTR
Date: Wed, 26 Mar 2014 22:06:49 +0000 [thread overview]
Message-ID: <8761n07gxy.fsf@sable.mobileactivedefense.com> (raw)
In-Reply-To: <1395870280.12610.252.camel@edumazet-glaptop2.roam.corp.google.com> (Eric Dumazet's message of "Wed, 26 Mar 2014 14:44:40 -0700")
Eric Dumazet <eric.dumazet@gmail•com> writes:
> On Wed, 2014-03-26 at 21:21 +0000, Rainer Weikusat wrote:
>> BTW, here's the program with the O_NONBLOCK read call which blocks until
>> the end of electricity, at least on 3.2.9:
>>
>> ---------
>> #include <fcntl.h>
>> #include <string.h>
>> #include <sys/socket.h>
>> #include <sys/un.h>
>>
>> int main(void)
>> {
>> struct sockaddr_un sun;
>> int fd;
>>
>> fd = socket(AF_UNIX, SOCK_DGRAM, 0);
>> sun.sun_family = AF_UNIX;
>> strncpy(sun.sun_path, "/tmp/bla", sizeof(sun.sun_path));
>> bind(fd, (struct sockaddr *)&sun, sizeof(sun));
>>
>> if (fork() == 0) read(fd, &fd, sizeof(fd));
>>
>> sleep(1);
>>
>> fcntl(fd, F_SETFL, O_NONBLOCK);
>> read(fd, &fd, sizeof(fd));
>>
>> return 0;
>> }
>
> Sure, O_NONBLOCK is translated into MSG_NOWAIT one time per socket
> syscall.
>
> Once we block, we don't automatically unblock if another thread change
> the file flag.
That would be a seriously bizarre idea. The thread of execution which
does the supposed-to-be-non-blocking call shouldn't become blocked for
an indefinite time. Which means it should not wait indefinitely for a
thread which - in turn - waits indefinitely for an external event (and
hence, the original problem should never have existed to begin with as
there would neither be an opportunity nor a reason to interrupt in the
non-blocking case).
BTW, while these are things which are of some interest to me (even of
some professional interest), I don't exactly get paid for these kind of
discussions, have some real work to do, and the way people interact on
LKML is seriously more aggressive then I can stand for a prolonged time,
so can we please end this discussion here while it - if only for a
change - hasn't yet degraded into an all out mutual extermination fight?
next prev parent reply other threads:[~2014-03-26 22:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-26 1:42 [PATCH] net: unix: non blocking recvmsg() should not return -EINTR Eric Dumazet
2014-03-26 13:17 ` Rainer Weikusat
2014-03-26 13:57 ` Rainer Weikusat
2014-03-26 14:09 ` Eric Dumazet
2014-03-26 14:25 ` Rainer Weikusat
2014-03-26 15:00 ` David Laight
2014-03-26 15:13 ` Rainer Weikusat
2014-03-26 15:25 ` Eric Dumazet
2014-03-26 15:33 ` Eric Dumazet
2014-03-26 19:46 ` Rainer Weikusat
2014-03-26 21:04 ` Rainer Weikusat
2014-03-27 9:36 ` David Laight
2014-03-27 12:40 ` Rainer Weikusat
2014-03-27 12:49 ` Jamal Hadi Salim
2014-03-27 13:02 ` Rainer Weikusat
2014-03-27 12:53 ` David Laight
2014-03-27 13:29 ` Rainer Weikusat
2014-03-26 21:05 ` David Miller
2014-03-26 21:21 ` Rainer Weikusat
2014-03-26 21:44 ` Eric Dumazet
2014-03-26 22:06 ` Rainer Weikusat [this message]
2014-03-26 22:35 ` Eric Dumazet
2014-03-26 22:51 ` Rainer Weikusat
2014-03-26 22:58 ` Eric Dumazet
2014-03-28 20:35 ` Rainer Weikusat
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=8761n07gxy.fsf@sable.mobileactivedefense.com \
--to=rweikusat@mobileactivedefense$(echo .)com \
--cc=David.Laight@ACULAB$(echo .)COM \
--cc=davem@davemloft$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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