loading multi threaded library into executable enabled for
single thread
Jeremy Chadwick
koitsu at FreeBSD.org
Fri Sep 12 16:09:03 UTC 2008
On Fri, Sep 12, 2008 at 11:55:01AM -0400, Barry Andrews wrote:
> Yes, the exe is tclsh. I understand that linking tclsh with libpthread is
> what would work. However this is very impractical. A user of my library
> shouldn't have to rebuild their tclsh to match my library specs. Another
> option would be to ship tclsh with my lib, but that also is a little weird.
> It seems like the only somewhat practical option I have is to use
> LD_PRELOAD, which is also weird but better than nothing.
This really isn't a "FreeBSD problem", as the same sort of issue plagues
other operating systems. When it comes to threading, you want
*everything* threaded as much as possible -- mix-matching usually does
not work. The only OS I have seen where that kind of environment works
reliably is Solaris. I still feel threading is "too new" of a
technology on UNIX.
Your options as I see them:
1) Require your users to ensure they have a threaded TCL installation,
and do not promise support in the case they try to use your library
on a non-threaded installation,
1) Provide two versions of your library -- a threaded and non-threaded
version. This may be impractical for performance reasons,
3) Require LD_PRELOAD, which is ugly, agreed.
I think those are pretty much the only options you have at this point.
Not a great set, I know, but it's reality.
> On Fri, Sep 12, 2008 at 11:45 AM, Jeremy Chadwick <koitsu at freebsd.org>wrote:
>
> > On Fri, Sep 12, 2008 at 11:00:18AM -0400, Barry Andrews wrote:
> > > Thanks for the links! But I'm not sure what any of this has to do with
> > > this particular issue. I have an exe that does not use threads that
> > > loads a lib that is linked with libpthread. Why does different threading
> > > implementations affect what I am seeing here? Is there no way for this
> > > to work in FreeBSD v5.5? Why would this go away if I upgraded to 6.x or
> > > better?
> >
> > You're confusing me. Earlier you said:
> >
> > >>>>>>> I have a multi-threaded library that is linked against libpthread.
> > >>>>>>> When I
> > >>>>>>> load this lib into a tclsh process on FreeBSD, I get this error,
> >
> > So what is "the exe?" Are you referring to tclsh? If so, you need to
> > rebuild tclsh from source to link with libpthread. If not, you need to
> > contact whoever provided the binary and ask them to rebuild it from
> > source.
> >
> > Additionally, please ensure that the tclsh binary is linked to the same
> > version of libpthread library as your own library. You want to make
> > sure they're both built and linked on the same machine (from the same
> > source code) if possible; the simple ".so.X" versioning method works
> > great for major changes, but there are often minor changes that don't
> > result in "X" being increased.
> >
> > I'm getting the impression that the tclsh binary you have was not built
> > on the same machine / from the same source as what your library (the one
> > linked with libpthread) was.
> >
> > > Jeremy Chadwick wrote:
> > >> On Fri, Sep 12, 2008 at 09:26:37AM -0400, Barry Andrews wrote:
> > >>
> > >>> I don't understand. If it was not broken, then why did it change in
> > later
> > >>> FreeBSD versions?
> > >>>
> > >>
> > >> I should be more explicit: the threading library and implementations
> > >> have changed over time. There was libc_r, then there was libthr, then
> > >> there was libkse. This is what we call "evolution". :-)
> > >>
> > >> http://www.unobvious.com/bsd/freebsd-threads.html
> > >> http://kerneltrap.org/node/624
> > >> http://www.freebsd.org/kse/
> > >>
> > >> The gcc -pthread flag is still there on present-day FreeBSD (6 through
> > >> HEAD), and *should* be used. You can choose not to use it but you must
> > >> ensure during linktime that you explicitly link to -lpthread.
> > >>
> > >>
> > >>> On Fri, Sep 12, 2008 at 9:10 AM, Jeremy Chadwick <koitsu at freebsd.org>
> > wrote:
> > >>>
> > >>>
> > >>>> On Fri, Sep 12, 2008 at 07:41:14AM -0400, Barry Andrews wrote:
> > >>>>
> > >>>>> Do you know if this is documented in Release Notes or Known Issues or
> > >>>>> somewhere?
> > >>>>>
> > >>>> Why would it be an "issue"? gcc -pthread and libpthread linking is
> > >>>> documented pretty much everywhere on the web. There isn't anything
> > >>>> broken about it, it's how it's done on older FreeBSD.
> > >>>>
> > >>>> Note that all of this has significantly changed in later FreeBSD
> > >>>> versions, and that the 5.x series was deprecated a very long time ago.
> > >>>>
> > >>>>
> > >>>>>> On Thu, 11 Sep 2008, Barry Andrews wrote:
> > >>>>>>
> > >>>>>>
> > >>>>>>> Hi All,
> > >>>>>>>
> > >>>>>>> I have a multi-threaded library that is linked against libpthread.
> > >>>>>>> When I
> > >>>>>>> load this lib into a tclsh process on FreeBSD, I get this error,
> > >>>>>>> "Recurse on
> > >>>>>>> private mutex". and crash. I understand that I can have this issue
> > >>>>>>> when the
> > >>>>>>> executable is not linked against libpthread but one of the loaded
> > >>>>>>> libs is.
> > >>>>>>> Basically, it thinks it's in single threaded mode.
> > >>>>>>>
> > >>>>>> This must be an older version of FreeBSD. I think you must
> > >>>>>> link your application (tclsh or whatever) against libpthread
> > >>>>>> in order for this to work. The libc functions won't get properly
> > >>>>>> overloaded by their equivalents in libpthread unless you do
> > >>>>>> this.
> > >>>>>>
> > >>>> --
> > >>>> | Jeremy Chadwick jdc at parodius.com|
> > >>>> | Parodius Networking http://www.parodius.com/|
> > >>>> | UNIX Systems Administrator Mountain View, CA, USA |
> > >>>> | Making life hard for others since 1977. PGP: 4BD6C0CB |
> > >>>>
> > >>>>
> > >>>>
> > >>> _______________________________________________
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> > >>
> > >>
> > >
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> >
> > --
> > | Jeremy Chadwick jdc at parodius.com |
> > | Parodius Networking http://www.parodius.com/ |
> > | UNIX Systems Administrator Mountain View, CA, USA |
> > | Making life hard for others since 1977. PGP: 4BD6C0CB |
> >
> >
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--
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
| Making life hard for others since 1977. PGP: 4BD6C0CB |
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