Deadlock in Gst::init()

[Kurt Miller <kurt intricatesoftware com>]

Using gstreamermm-0.10.10.1 with gstreamer-0.10.36 Gst::init()
indirectly attempts a recursive load of the adder plugin. The
recursive load deadlocks due to the use of a static mutex in
gst_plugin_load_by_name(). This is reproduceable with
subtitleeditor on OpenBSD HEAD/current.

Here is the stack trace showing the recursive call to
gst_plugin_load_by_name():

#2  0x0009c065 in _rthread_mutex_lock (mutexp=0x7c1e6670, trywait=0, abstime=0x0) at /usr/src/lib/librthread/rthread_sync.c:127
#3  0x08c68ec2 in g_mutex_lock () from /usr/local/lib/libglib-2.0.so.3200.0
#4  0x02f1f3e5 in gst_plugin_load_file (filename=0x7c1f6580 "/usr/local/lib/gstreamer-0.10/libgstadder.so", error=0xcfbc0bc8)
    at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:722
#5  0x02f2022b in gst_plugin_load_by_name (name=0x7c3c2bf5 "adder") at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:1297
#6  0x02f2185d in gst_plugin_feature_load (feature=0x7c3c32e8) at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstpluginfeature.c:111
#7  0x0b5e3954 in gst_adder_get_type () at /usr/obj/ports/gstreamermm-0.10.10.1/gstreamermm-0.10.10.1/gstreamer/gstreamermm/adder.cc:29
#8  0x0ff679e1 in plugin_init (plugin=0x7c397d48) at /usr/obj/ports/gst-plugins-base-0.10.36/gst-plugins-base-0.10.36/gst/adder/gstadder.c:1322
#9  0x02f1e6ff in gst_plugin_register_func (plugin=0x7c397d48, desc=0x2ff66020, user_data=0x0)
    at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:557
#10 0x02f1f611 in gst_plugin_load_file (filename=0x7c1f6580 "/usr/local/lib/gstreamer-0.10/libgstadder.so", error=0xcfbc0dc8)
    at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:843
#11 0x02f2022b in gst_plugin_load_by_name (name=0x7c3c2bf5 "adder") at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:1297
#12 0x02f2185d in gst_plugin_feature_load (feature=0x7c3c32e8) at /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstpluginfeature.c:111
#13 0x0b5e3954 in gst_adder_get_type () at /usr/obj/ports/gstreamermm-0.10.10.1/gstreamermm-0.10.10.1/gstreamer/gstreamermm/adder.cc:29
#14 0x0b624d21 in Gst::wrap_init () at /usr/obj/ports/gstreamermm-0.10.10.1/gstreamermm-0.10.10.1/gstreamer/gstreamermm/wrap_init.cc:386
#15 0x0b6258d0 in initialize_wrap_system () at /usr/obj/ports/gstreamermm-0.10.10.1/gstreamermm-0.10.10.1/gstreamer/gstreamermm/init.cc:36
#16 0x0b625a77 in Gst::init (argc=@0xcfbc0fb4, argv=@0xcfbc0fb8)
    at /usr/obj/ports/gstreamermm-0.10.10.1/gstreamermm-0.10.10.1/gstreamer/gstreamermm/init.cc:53
#17 0x1c01d13c in Glib::PropertyProxy<Glib::ustring>::get_value ()

Here are the debug messages:

GST_INIT /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gst.c:805:init_post: GLib runtime version: 2.32.2
GST_INIT /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gst.c:807:init_post: GLib headers version: 2.32.2
GST_INIT /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gst.c:437:gst_init_check: already initialized gst
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<adder> 0x7c3c32e8 ref 1->2
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstpluginfeature.c:106:gst_plugin_feature_load: loading plugin for feature 0x7c3c32e8; 'adder'
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstpluginfeature.c:110:gst_plugin_feature_load: loading plugin adder
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:1293:gst_plugin_load_by_name: looking up plugin adder in default registry
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<plugin96> 0x7c397d48 ref 1->2
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<plugin96> 0x7c397d48 ref 2->3
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:337:gst_object_unref:<plugin96> 0x7c397d48 unref 3->2
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:1296:gst_plugin_load_by_name: loading plugin adder from file /usr/local/lib/gstreamer-0.10/libgstadder.so
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<plugin96> 0x7c397d48 ref 2->3
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:737:gst_plugin_load_file: attempt to load plugin "/usr/local/lib/gstreamer-0.10/libgstadder.so"
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:834:gst_plugin_load_file: Plugin 0x7c397d48 for file "/usr/local/lib/gstreamer-0.10/libgstadder.so" prepared, calling entry function...
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:841:gst_plugin_load_file: Plugin 0x7c397d48 for file "/usr/local/lib/gstreamer-0.10/libgstadder.so" prepared, registering...
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:540:gst_plugin_register_func: plugin "/usr/local/lib/gstreamer-0.10/libgstadder.so" looks good
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<adder> 0x7c3c32e8 ref 2->3
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstpluginfeature.c:106:gst_plugin_feature_load: loading plugin for feature 0x7c3c32e8; 'adder'
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstpluginfeature.c:110:gst_plugin_feature_load: loading plugin adder
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:1293:gst_plugin_load_by_name: looking up plugin adder in default registry
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<plugin96> 0x7c397d48 ref 3->4
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:311:gst_object_ref:<plugin96> 0x7c397d48 ref 4->5
GST_REFCOUNTING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstobject.c:337:gst_object_unref:<plugin96> 0x7c397d48 unref 5->4
GST_PLUGIN_LOADING /usr/obj/ports/gstreamer-0.10.36/gstreamer-0.10.36/gst/gstplugin.c:1296:gst_plugin_load_by_name: loading plugin adder from file /usr/local/lib/gstreamer-0.10/libgstadder.so

It is not clear to me what globals are being protected by the
gst_plugin_loading_mutex in gst/gstplugin.c gst_plugin_load_file().
Perhaps the scope of the lock is to0 broad covering the potential
recursion caused by the call to gst_plugin_register_func().

Any pointers on how to address this problem would be appreciated.

Thanks,
-Kurt