gdk_threads_enter versus sgtk_init_threads

[Kevin Ryde <user42@zip.com.au>]

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I believe sgtk_init_threads is being called too late to influence
gdk_threads_enter and gdk_threads_leave, and that instead they're
ending up as noops.

The program threads.scm below illustrates the problem, threads 1, 2
and 3 are able to "enter" all at the same time.  I've using a recent
i386 debian with the guile cvs and pthreads for this,

	1 entering
	1 entered
	2 entering
	2 entered
	3 entering
	3 entered
	...

Adding a printf of gdk_threads_mutex to the generated
sgtk_gdk_threads_enter reveals NULL.  I'm pretty sure gtk_init has
called gdk_init which has initialized it's threading before
sgtk_init_threads has had a chance to setup the glib level stuff.

I get some joy from moving the sgtk_init_threads call from
sgtk_init_substrate to the start of sgtk_init_with_args (before
gtk_init).  This exposes however that gdk-threads-enter shouldn't be
using SCM_DEFER_INTS, since of course it needs other threads to run to
release the mutex.

        * gdk-1.2.defs (gdk_threads_enter, gdk_threads_leave): Add undeferred,
        since these are thread safe, and in particular enter needs other
        threads runnable to release the mutex.
        * guile-gtk.c (sgtk_init_substrate): Move sgtk_init_threads ....
        (sgtk_init_with_args): ... to here, to ensure glib threading is setup
        before gtk_init and gdk_init run.

It might be nice if the glib level inits were separated, for clarity.
Perhaps that can wait until there's an actual glib module though.


[-- Attachment #2: threads.scm --]
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(use-modules (ice-9 threads)
	     (gtk gtk)
	     (gtk gdk))

(begin-thread
 (display "1 entering\n")
 (gdk-threads-enter)
 (display "1 entered\n")
 (sleep 2)
 (display "1 leaving\n")
 (gdk-threads-leave)
 (display "1 left\n"))

(begin-thread
 (display "2 entering\n")
 (gdk-threads-enter)
 (display "2 entered\n")
 (sleep 2)
 (display "2 leaving\n")
 (gdk-threads-leave)
 (display "2 left\n"))

(begin-thread
 (display "3 entering\n")
 (gdk-threads-enter)
 (display "3 entered\n")
 (sleep 2)
 (display "3 leaving\n")
 (gdk-threads-leave)
 (display "3 left\n"))

(sleep 20)

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--- guile-gtk.c.~1.15.~	2003-05-24 10:02:45.000000000 +1000
+++ guile-gtk.c	2003-05-24 10:02:57.000000000 +1000
@@ -2774,8 +2774,6 @@
 
   callback_trampoline = scm_permanent_object (scm_cons (SCM_BOOL_F, SCM_EOL));
 
-  sgtk_init_threads ();
-
 #ifndef SCM_MAGIC_SNARFER
 #ifndef MKDEP
 #include "guile-gtk.x"
@@ -2795,6 +2793,8 @@
      been initialized when Gdk has.  That is not completely correct,
      but the best I can do. */
 
+  sgtk_init_threads ();
+
   if (gdk_display == NULL)
     {
       gtk_set_locale ();

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--- gdk-1.2.defs.~1.28.~	2003-05-19 10:26:58.000000000 +1000
+++ gdk-1.2.defs	2003-05-23 14:58:39.000000000 +1000
@@ -1737,11 +1737,13 @@
 
 (define-func gdk_threads_enter
   none
-  ())
+  ()
+  (undeferred #t))
 
 (define-func gdk_threads_leave
   none
-  ())
+  ()
+  (undeferred #t))
 
 ;; gdkrgb