mysterious hang in pthread_create

[Kostik Belousov]

On Fri, Aug 29, 2008 at 12:25:09PM -0400, Daniel Eischen wrote:
> On Fri, 29 Aug 2008, Kostik Belousov wrote:
> 
> >On Fri, Aug 29, 2008 at 05:18:18PM +0300, Andriy Gapon wrote:
> >>
> >>Kostik, thanks!
> >>
> >>on 29/08/2008 17:10 Kostik Belousov said the following:
> >>>I am wondering why did you not fixed it youself with all this 
> >>>information.
> >>
> >>I am wondering that myself now :-)
> >>I got bogged in rtld details and simply didn't think about the solution
> >>of doing setthreaded earlier.
> >>
> >>I will try your patch a couple of hours later.
> >>BTW, a forward question - should this patch help in the case of an
> >>exception thrown (and caught) before main(), i.e. in constructors of
> >>static/global objects?
> >If the objects are from the executable, then yes. I do not know about
> >present situation, but some time ago g++ and several other compilers
> >called ctr for global objects from the main() function. Regardeless
> >of this, init for main executable shall be called after init for
> >dependencies is finished. See initlist_add_objects().
> >
> >On the other hand, ctr calls from linked dso may get fixed in regard
> >of exception throwing, or may not, depending on the relative order of
> >the dso loading against libthr.
> >
> >>
> >>>Anyway, patch below seems to work for me. David may have an opinion on
> >>>the change.
> >>>
> >>>diff --git a/lib/libthr/thread/thr_init.c b/lib/libthr/thread/thr_init.c
> >>>index f96bba9..785d610 100644
> >>>--- a/lib/libthr/thread/thr_init.c
> >>>+++ b/lib/libthr/thread/thr_init.c
> >>>@@ -355,6 +355,9 @@ _libpthread_init(struct pthread *curthread)
> >>> 		if (_thread_event_mask & TD_CREATE)
> >>> 			_thr_report_creation(curthread, curthread);
> >>> 	}
> >>>+
> >>>+	if (_thr_isthreaded() == 0)
> >>>+		_thr_setthreaded(1);
> >>> }
> >>>
> >>> /*
> 
> I think the intent of __isthreaded (and _thr_setthreaded()) was
> to be set if there were more than 1 thread, not to indicate that
> the thread library has been initialized.

As demonstrated by Andriy' example, we need _thr_rtld_init() be called
before any rtld locks are given chance to be acquired. _thr_rtld_init()
shall be protected from repeated invocation, and _thr_setthreaded()
implements exactly this.

If calling _thr_setthreaded(1) has not quite right intent, could you,
please, suggest satisfying solution ?

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