>>> On 7/4/2012 at 10:30 AM, Chris Vine <chris@xxxxxxxxxxxxxxxxxxxxx>
wrote:
> On Tue, 03 Jul 2012 20:59:11 +0200
> "Martin Schlemmer" <Martin.Schlemmer@xxxxxxxxx> wrote:
>> Hi,
>>
>> Bit long, sorry.
>>
>> I build my own GTK+ stack with MinGW (TDM-4.6.1) and have been
using
>> 2.16 and Glib 2.28 (with Gtk2-Perl bindings mostly) for a long
time,
>> then switched to GTK+ 2.24 when that started to get stable enough.
>> Wanting to start with WebKit I switched to Glib 2.30 to be able to
>> use GObject-Introspection from Dieter's git repo.
>>
>> This still worked fine, but needing later G-O-I interfaces from
>> WebKit, I tried to build 1.8 which needs Glib 2.31 or later, so I
>> switched to Glib 2.32.3, and this is where my problems started.
>>
>> All threaded Gtk2-Perl apps locked up on startup and I initially
>> thought it was a Gtk2-Perl problem, but building the example from
the
>> FAQ:
>>
>> http://developer.gnome.org/gtk-faq/stable/x481.html
>>
>> result in the same problem. The easiest way to reproduce it is to
>> start the example and then move the window which immediately
results
>> in a deadlock.
>
> GTK+/GDK has never been thread-safe on Win32. If the GDK global
lock
> appeared to work for you in the past you just got lucky. From the
> documentation at
> http://developer.gnome.org/gdk/stable/gdk-Threads.html :
>
> "GTK+ is "thread aware" but not thread safe * it provides a global
lock
> controlled by gdk_threads_enter()/gdk_threads_leave() which protects
> all use of GTK+. That is, only one thread can use GTK+ at any given
> time.
>
> "Unfortunately the above holds with the X11 backend only. With the
Win32
> backend, GDK calls should not be attempted from multiple threads at
> all."
>
> In due course
gdk_threads_init()/gdk_threads_enter()/gdk_threads_leave()
> are to be deprecated in the X11 backend, although that is not
relevant
> to your code.
>
> Win32 users (and in due course X11 users) should use
> g_idle_add()/g_idle_add_full() to send event callbacks from worker
> threads to the gui thread which invoke the GTK+ functions you want
to
> call. With glib < 2.32, you will need to call g_thread_init()
> (g_thread_init() is not needed on glib >= 2.32 and is a no-op.)
This
> also happens to be a much cleaner design than using the GDK global
lock.
>
> The FAQ on this is, I agree, misleading - I should file a
documentation
> bug.
>
I understand this, and that is why I modified the example to do exactly
that - use g_idle_add().
The problem currently as far as I can see it, is that when processing
events with the GDK global lock taken in gdk_event_dispatch(), as soon
as its a modal operation gets queued in
_gdk_win32_display_queue_events(), modal_timer_proc() gets called which
calls g_main_context_pending() and you eventually end up in
gdk_event_prepare() which tries to take the GDK global lock for a second
time in the same thread ...
Just to test, I removed any threads, and the problem persists with the
same backtrace (see below).
Anyhow, below patch (also attached) fixes it by not calling
_gdk_win32_display_queue_events() with the lock held, if anybody can
have a look if there are any locking problems I would appreciate it.
-----
diff --git a/gdk/win32/gdkevents-win32.c b/gdk/win32/gdkevents-win32.c
index 2bc7c12..3505fe2 100644
--- a/gdk/win32/gdkevents-win32.c
+++ b/gdk/win32/gdkevents-win32.c
@@ -3369,9 +3369,10 @@ gdk_event_dispatch (GSource *source,
{
GdkEvent *event;
+ _gdk_win32_display_queue_events (_gdk_display);
+
GDK_THREADS_ENTER ();
- _gdk_win32_display_queue_events (_gdk_display);
event = _gdk_event_unqueue (_gdk_display);
if (event)
-----
Thanks,
Martin
-----
int main(int argc, char *argv[])
{
GtkWidget *window;
GtkWidget *label;
gdk_threads_init();
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
g_signal_connect(window, "destroy",
G_CALLBACK(destroy), NULL);
gtk_container_set_border_width(GTK_CONTAINER (window), 10);
label = gtk_label_new("And now for something completely different
...");
gtk_container_add(GTK_CONTAINER(window), label);
gtk_widget_show(label);
gtk_widget_show (window);
gdk_threads_enter();
gtk_main();
gdk_threads_leave();
return 0;
}
-----
Vrywaringsklousule / Disclaimer:
http://www.nwu.ac.za/it/gov-man/disclaimer.html
diff --git a/gdk/win32/gdkevents-win32.c b/gdk/win32/gdkevents-win32.c
index 2bc7c12..3505fe2 100644
--- a/gdk/win32/gdkevents-win32.c
+++ b/gdk/win32/gdkevents-win32.c
@@ -3369,9 +3369,10 @@ gdk_event_dispatch (GSource *source,
{
GdkEvent *event;
+ _gdk_win32_display_queue_events (_gdk_display);
+
GDK_THREADS_ENTER ();
- _gdk_win32_display_queue_events (_gdk_display);
event = _gdk_event_unqueue (_gdk_display);
if (event)
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