Re: Strange dead lock with g_threads_enter

[Wei-Ning Huang <aitjcize gmail com>]

Thanks Chris. I tried to remove any function call in the compile_thread,
i.e:

// Thread function
// It is signaled to wake up for every 1 second
gpointer motion_compile_thread(gpointer data) {
...
   while (TRUE) {
     if (!g_mutex_trylock(cp_mutex)) continue;
     g_cond_wait(compile_cv, cp_mutex);
     g_mutex_unlock(mutex);
}

Now that what the thread does is simply wake up every 1 second (signaled by
the main thread) and go back to sleep.
It STILL deadlocked!!!
I tried running this on ubuntu 10.10, and it worked perfectly fine (no
deadlock)

I'm starting to think it's the bug of gtk+, or perhaps the kernel?
btw, I'm using Arch Linux with Kernel 2.6.37(autogroup patched), Gtk+ 2.22.

SI once suspect that it maybe something to do with the autogroup patch I'm
using, so I switch to the
default 2.6.37 kernel. The result is the same.. still deadlocks.

frustrated ... (but glad that this didn't happen on ubuntu)

Thanks,
Wei-Ning Huang

2011/3/5 Chris Vine <chris cvine freeserve co uk>

> On Sat, 5 Mar 2011 11:58:23 +0800
> Wei-Ning Huang <aitjcize gmail com> wrote:
> [snip]
> > From what I can see, the program is stuck because the main thread
> > locked a mutex in #3.
> > But from the backtrace, the mutex seems to be locked by
> > gtk_main_loop_run() which is something I can't control,
> > and somehow it locked the same mutex as gdk_threads_enter()? any
> > ideas?
>
> If it isn't recursion then somewhere in your '....' you probably have
> out-of-order locking.
>
> I should start by making the gdk global lock 'Lock 1' and work from
> there. In other words, don't call gdk_threads_enter() when you are
> holding a lock of your own.  Also, don't call gdk_threads_enter() in a
> GTK+ signal handler because it will already be locked there.  (But that
> is not true of ordinary glib main loop events.)
>
> Best of all, don't use the global lock at all but instead invoke
> callbacks in the main loop with g_idle_add().   This is a cleaner
> design and also has the benefit of making your program portable to
> windows and other non-X11 platforms.
>
> Chris


-- 
AZ Huang <http://berelent.blogspot.com/>