[patch] Re: dlopen() and dlclose() are not MT-safe? YES, esp. for libthr

Kazuaki Oda kaakun at highway.ne.jp
Fri Mar 24 12:00:09 UTC 2006

Kostik Belousov wrote:
> I did understand the purpose of the thread mask code in
> libexec/rtld/rtld_lock.c, or, more precisely, the condition where this code
> works (for the context, see the mails with same subject on freebsd-hackers).
> Look, that code assumes that blocking async signals would stop thread
> scheduler from doing preemption of the current thread. This works
> for libc_r, but fails in libpthread and libthr cases. libpthread provides
> implementation of the locks for rtld. But libthr does not !
> As result, rtld exhibit races when used with libthr. In other words,
> libthr needs code to do proper locking.
> Do you agree ? Does somebody already planned to do this work ?
> Best regards,
> Kostik Belousov

I'm a bit confused.  Do you mean the following?

* The current implementation of rtld has a problem both with
  libpthread and libthr.  It works only with libc_r.
* In libpthread case, the problem goes away if we modify rtld code.
* In libthr case, in addition to above, we must modify libthr code to
  provide implementation of the locks for rtld.


Kazuaki Oda

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