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

On Fri, Mar 24, 2006 at 08:54:34PM +0900, Kazuaki Oda wrote:
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.
It does not work correctly with libc_r too.
* In libpthread case, the problem goes away if we modify rtld code.
Yes.
* In libthr case, in addition to above, we must modify libthr code to
provide implementation of the locks for rtld.
Yes.

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