Groups > comp.programming.threads > #2008

Re: Open issues in the specification for fork()?

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Date	Mon, 25 Nov 2013 01:19:03 +0000
From	Chris Vine <chris@cvine--nospam--.freeserve.co.uk>
Newsgroups	comp.programming.threads, comp.unix.programmer
Subject	Re: Open issues in the specification for fork()?
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On 25 Nov 2013 00:23:05 GMT
Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> wrote:
[snip]
> I think this is completely unfair as it are those who worked on the
> implementation and those who wrote the standard knew exactly the
> two choices they had; they picked one of the two choices and you
> seem to disagree with that particular choice.

It was also in my view the better choice - I just don't like forkall(),
as it can make the program more difficult to reason about, particularly
for programs using a shared resource such as I/O (and what don't),
which can turn forkall() into a bug factory.

The only purpose for calling POSIX fork() in a multi-threaded program is
to follow it with a call to exec*() (perhaps after setting up pipes with
dup2() and the like), in which case the async-signal-safe restriction
is fine: you do your other set up (including any memory allocation)
before the fork() and not after. For other purposes, in a
multi-threaded program conforming to POSIX you start a thread, not a
process.

pthread_atfork() is completely broken.  That can cause problems with
single threaded programs that use multi-threaded libraries without
taking the care to understand that what they are linking to is
multi-threaded, but there we are.  Know what you are linking to is, I
guess, the best answer.

Chris

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Thread

Open issues in the specification for fork()? Markus Elfring <Markus.Elfring@web.de> - 2013-11-23 19:05 +0100
  Re: Open issues in the specification for fork()? Måns Rullgård <mans@mansr.com> - 2013-11-23 18:32 +0000
  Re: Open issues in the specification for fork()? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2013-11-23 22:13 +0000
    Re: Open issues in the specification for fork()? Markus Elfring <Markus.Elfring@web.de> - 2013-11-24 06:56 +0100
  Re: Open issues in the specification for fork()? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-11-24 10:27 +0000
    Re: Open issues in the specification for fork()? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2013-11-24 15:39 +0000
      Re: Open issues in the specification for fork()? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-11-25 00:23 +0000
        Re: Open issues in the specification for fork()? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2013-11-25 01:19 +0000
          Re: Open issues in the specification for fork()? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-11-25 12:08 +0000
            Re: Open issues in the specification for fork()? Drazen Kacar <dave@fly.srk.fer.hr> - 2013-11-25 18:46 +0000
              Re: Open issues in the specification for fork()? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-11-25 19:55 +0000
                Re: Open issues in the specification for fork()? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2013-11-25 22:16 +0000
                Re: Open issues in the specification for fork()? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-11-26 08:33 +0000
                Re: Open issues in the specification for fork()? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2013-11-26 15:46 +0000
          Re: Open issues in the specification for fork()? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2013-11-25 12:21 +0000
        Re: Open issues in the specification for fork()? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2013-11-25 15:52 +0000
          Re: Open issues in the specification for fork()? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2013-11-25 16:55 +0000
            Re: Open issues in the specification for fork()? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2013-11-25 17:36 +0000
  Re: Open issues in the specification for fork()? Kaz Kylheku <kaz@kylheku.com> - 2014-01-26 03:45 +0000

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