Re: threads, signals, and atomicity of basic types

From	Nobody <nobody@nowhere.com>
Subject	Re: threads, signals, and atomicity of basic types
Date	2011-06-15 17:41 +0100
Message-Id	<pan.2011.06.15.16.40.50.63000@nowhere.com>
Newsgroups	comp.unix.programmer
References	(9 earlier) <jCQJp.36914$675.21379@news.usenetserver.com> <pan.2011.06.15.02.07.20.219000@nowhere.com> <87mxhjbg9z.fsf@sapphire.mobileactivedefense.com> <4df87e07$0$49044$e4fe514c@news.xs4all.nl> <87r56vi8vi.fsf@sapphire.mobileactivedefense.com>
Organization	Zen Internet

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On Wed, 15 Jun 2011 13:20:33 +0100, Rainer Weikusat wrote:

> Playing devil's advocate for the moment: Since pthread_mutex_lock is a
> standardized function, the compiler might  know that it won't
> change a

The compiler doesn't know which libraries you are going to link against.
It cannot assume that you're going to be linking against the "official"
unmodified libpthread, with a known implementation of pthread_mutex_lock().

If you look at how "intrinsics" are implemented, it relies upon the header
file defining (or redirecting) the function as some __builtin_function()
which the compiler recognises. If you desire, you can override the
definition to cause the function to be a normal external reference which
will be resolved by the libraries which are loaded at run time.

And if the compiler /did/ know about pthread_mutex_lock(), it would know
that calling it would block until the lock was released, and that
whichever thread was holding the lock might modify "a" in the meantime.
Even declaring "a" as "static" wouldn't help here, as the other thread
might be running some function (in the same source file) which modifies "a".

Thread

threads, signals, and atomicity of basic types Urs Thuermann <urs@isnogud.escape.de> - 2011-05-31 21:07 +0200
  Re: threads, signals, and atomicity of basic types Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2011-05-31 22:44 +0200
    Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-01 11:58 +0100
      Re: threads, signals, and atomicity of basic types Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2011-06-01 14:15 +0200
        Re: threads, signals, and atomicity of basic types Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2011-06-02 13:49 +0200
          Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-02 13:40 +0100
  Re: threads, signals, and atomicity of basic types Richard Kettlewell <rjk@greenend.org.uk> - 2011-05-31 22:50 +0100
  Re: threads, signals, and atomicity of basic types Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-05-31 21:32 -0400
    Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-01 12:35 +0100
      Re: threads, signals, and atomicity of basic types Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-01 23:01 -0400
        Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-02 11:22 +0100
          Re: threads, signals, and atomicity of basic types Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-02 07:52 -0400
            Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-02 13:38 +0100
              Re: threads, signals, and atomicity of basic types Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-02 21:27 -0400
  Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-01 12:55 -0700
    Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-01 22:54 +0100
      Re: threads, signals, and atomicity of basic types Alex Fraser <me@privacy.net> - 2011-06-02 21:00 +0100
        Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-04 21:53 -0700
          Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-05 16:39 +0100
            Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-06 18:48 -0700
              Re: threads, signals, and atomicity of basic types Nobody <nobody@nowhere.com> - 2011-06-07 06:50 +0100
                Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-07 06:04 -0700
                Re: threads, signals, and atomicity of basic types Nobody <nobody@nowhere.com> - 2011-06-07 22:48 +0100
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-07 23:18 +0100
                Re: threads, signals, and atomicity of basic types gordonb.lhpq6@burditt.org (Gordon Burditt) - 2011-06-07 18:28 -0500
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-08 11:09 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-08 14:32 -0700
                Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-09 18:10 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-10 15:26 +0100
                Re: threads, signals, and atomicity of basic types James Waldby <not@valid.invalid> - 2011-06-10 16:49 +0000
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-10 19:07 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-10 13:13 -0700
              Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-07 12:55 +0100
                Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-07 06:02 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-07 16:05 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-07 13:37 -0700
                Re: threads, signals, and atomicity of basic types scott@slp53.sl.home (Scott Lurndal) - 2011-06-14 21:43 +0000
                Re: threads, signals, and atomicity of basic types Nobody <nobody@nowhere.com> - 2011-06-15 03:07 +0100
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-15 10:22 +0100
                Re: threads, signals, and atomicity of basic types Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2011-06-15 09:40 +0000
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-15 13:20 +0100
                Re: threads, signals, and atomicity of basic types Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2011-06-15 13:19 +0000
                Re: threads, signals, and atomicity of basic types Nobody <nobody@nowhere.com> - 2011-06-15 17:41 +0100
                Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-15 20:20 -0700
                Re: threads, signals, and atomicity of basic types Nobody <nobody@nowhere.com> - 2011-06-15 17:31 +0100
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-15 18:31 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-15 13:32 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-15 22:19 +0100
                Re: threads, signals, and atomicity of basic types Nobody <nobody@nowhere.com> - 2011-06-16 05:02 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-14 23:23 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-15 10:12 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-15 02:53 -0700
                Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-08 10:19 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-10 16:50 +0100
                Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-15 20:24 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-16 22:11 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-17 04:43 -0700
                Re: threads, signals, and atomicity of basic types Michael Press <rubrum@pacbell.net> - 2011-06-19 01:43 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-19 13:35 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-19 17:06 -0700
                Re: threads, signals, and atomicity of basic types scott@slp53.sl.home (Scott Lurndal) - 2011-06-20 16:22 +0000
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-20 19:16 +0100
                Re: threads, signals, and atomicity of basic types scott@slp53.sl.home (Scott Lurndal) - 2011-06-21 17:30 +0000
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-21 13:02 -0700
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-20 14:32 -0700
                Re: threads, signals, and atomicity of basic types scott@slp53.sl.home (Scott Lurndal) - 2011-06-21 17:05 +0000
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-19 17:01 -0700
                Re: threads, signals, and atomicity of basic types Michael Press <rubrum@pacbell.net> - 2011-06-22 01:55 -0700
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-22 03:36 -0700
      Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-02 21:53 -0700
      Re: threads, signals, and atomicity of basic types David Schwartz <davids@webmaster.com> - 2011-06-03 04:24 -0700
      Re: threads, signals, and atomicity of basic types Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-03 07:52 -0400
  Re: threads, signals, and atomicity of basic types "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2011-06-02 00:23 +0200
    Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-01 20:11 -0700
      Re: threads, signals, and atomicity of basic types "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2011-06-02 22:54 +0200
        Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-02 14:03 -0700
          Re: threads, signals, and atomicity of basic types "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2011-06-03 02:49 +0200
            Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-02 17:54 -0700
              Re: threads, signals, and atomicity of basic types Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-02 21:36 -0400
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-03 16:25 +0100
            Re: threads, signals, and atomicity of basic types "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2011-06-03 03:12 +0200
  Re: threads, signals, and atomicity of basic types "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2011-06-02 00:45 +0200
    Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-02 11:26 +0100
      Re: threads, signals, and atomicity of basic types Alex Fraser <me@privacy.net> - 2011-06-02 21:05 +0100
  Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-01 20:21 -0700
    Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-02 11:31 +0100
      Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-02 09:12 -0700
        Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-02 17:54 +0100
          Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-02 14:00 -0700
            Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-03 15:19 +0100
              Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-03 15:50 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-05 16:46 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-05 15:28 -0700
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-06 13:35 +0100
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-06 09:19 -0700
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-06 09:26 -0700
                Re: threads, signals, and atomicity of basic types Ian Collins <ian-news@hotmail.com> - 2011-06-07 09:43 +1200
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-07 13:29 +0100
                Re: threads, signals, and atomicity of basic types Ian Collins <ian-news@hotmail.com> - 2011-06-08 09:04 +1200
                Re: threads, signals, and atomicity of basic types Rainer Weikusat <rweikusat@mssgmbh.com> - 2011-06-08 12:34 +0100
                Re: threads, signals, and atomicity of basic types Ian Collins <ian-news@hotmail.com> - 2011-06-09 07:37 +1200
                Re: threads, signals, and atomicity of basic types Joshua Maurice <joshuamaurice@gmail.com> - 2011-06-07 14:55 -0700

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