mysterious hang in pthread_create

Kostik Belousov kostikbel at
Mon Sep 1 11:12:21 UTC 2008

On Mon, Sep 01, 2008 at 01:53:23PM +0300, Andriy Gapon wrote:
> on 01/09/2008 11:45 Kostik Belousov said the following:
> >On Mon, Sep 01, 2008 at 11:34:45AM +0300, Andriy Gapon wrote:
> >>on 01/09/2008 11:10 David Xu said the following:
> >>>The ancient bug is in rtld, rlock_acquire() and wlock_acquire() test
> >>>thread_flag as a boolean value, because pt_iterate_phdr() tries to
> >>>lock two locks at same time, this test will always fail once it
> >>>acquired first lock.
> >>>
> >>>The following silly patch fixes the problem Andriy encountered:
> >>I can confirm - this fixed the issue for me.
> >>David, thanks!
> >
> >Does libc_r still work with patch applied ?
> In what sense?
> The test program that I posted seems to hang in both cases (patched and 
> unpatched rtld).

The David' patch changes the code used to support libc_r operations.
Even on CURRENT, if you run 4.x-compiled binary with the support of
compat-4x libraries, this code from /libexec/ (installed
by CURRENT buildworld) provides locking for rtld.
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