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display: add a specific lock for the list of windows

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It's either this or replacing all the object lock usage in gldisplay
with a recursive mutex which is not backwards compatible

The failure case is effectively:
1. The user has locked the display object lock
2. a glcontext loses it's last ref and attempts to quit the window
3. gst_gl_window_quit() attempts to remove the window from the display
4. gst_gl_display_remove_window attempts to take the display object lock

The only concern with changing the locking for the window list in the
display is that gst_gl_display_create_window() has documentation requiring
the object lock to be held which must continue to work correctly.
This commit is contained in:
Matthew Waters 2019-11-03 00:46:49 +11:00 committed by GStreamer Merge Bot
parent b887db1efe
commit 3b552cc05a
2 changed files with 14 additions and 7 deletions
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19
gst-libs/gst/gl/gstgldisplay.c
View file

@ -110,6 +110,8 @@ struct _GstGLDisplayPrivate
GMutex thread_lock;
GCond thread_cond;
GMutex window_lock;
};
#define DEBUG_INIT \
@ -194,6 +196,8 @@ gst_gl_display_init (GstGLDisplay * display)
g_mutex_init (&display->priv->thread_lock);
g_cond_init (&display->priv->thread_cond);
g_mutex_init (&display->priv->window_lock);
display->priv->event_thread = g_thread_new ("gldisplay-event",
(GThreadFunc) _event_thread_main, display);
@ -259,6 +263,7 @@ gst_gl_display_finalize (GObject * object)
g_cond_clear (&display->priv->thread_cond);
g_mutex_clear (&display->priv->thread_lock);
g_mutex_clear (&display->priv->window_lock);
G_OBJECT_CLASS (gst_gl_display_parent_class)->finalize (object);
}
@ -576,10 +581,10 @@ gst_gl_display_create_context (GstGLDisplay * display,
* gst_gl_display_create_window:
* @display: a #GstGLDisplay
*
* It requires the display's object lock to be held.
*
* Returns: (transfer full): a new #GstGLWindow for @display or %NULL.
*/
/* XXX: previous versions had documentation requiring the OBJECT lock to be
* held when this fuction is called so that needs to always work. */
GstGLWindow *
gst_gl_display_create_window (GstGLDisplay * display)
{
@ -590,11 +595,13 @@ gst_gl_display_create_window (GstGLDisplay * display)
klass = GST_GL_DISPLAY_GET_CLASS (display);
g_return_val_if_fail (klass->create_window != NULL, NULL);
g_mutex_lock (&display->priv->window_lock);
window = klass->create_window (display);
if (window) {
display->windows = g_list_prepend (display->windows, window);
}
g_mutex_unlock (&display->priv->window_lock);
GST_DEBUG_OBJECT (display, "Adding window %" GST_PTR_FORMAT
" (%p) to internal list", window, window);
@ -622,7 +629,7 @@ gst_gl_display_remove_window (GstGLDisplay * display, GstGLWindow * window)
gboolean ret = FALSE;
GList *l;
GST_OBJECT_LOCK (display);
g_mutex_lock (&display->priv->window_lock);
l = g_list_find (display->windows, window);
if (l) {
display->windows = g_list_delete_link (display->windows, l);
@ -630,7 +637,7 @@ gst_gl_display_remove_window (GstGLDisplay * display, GstGLWindow * window)
}
GST_DEBUG_OBJECT (display, "Removing window %" GST_PTR_FORMAT
" (%p) from internal list", window, window);
GST_OBJECT_UNLOCK (display);
g_mutex_unlock (&display->priv->window_lock);
return ret;
}
@ -687,14 +694,14 @@ gst_gl_display_retrieve_window (GstGLDisplay * display, gpointer data,
GstGLWindow *ret = NULL;
GList *l;
GST_OBJECT_LOCK (display);
g_mutex_lock (&display->priv->window_lock);
l = g_list_find_custom (display->windows, data, compare_func);
if (l)
ret = gst_object_ref (l->data);
GST_DEBUG_OBJECT (display, "Found window %" GST_PTR_FORMAT
" (%p) in internal list", ret, ret);
GST_OBJECT_UNLOCK (display);
g_mutex_unlock (&display->priv->window_lock);
return ret;
}

2
gst-libs/gst/gl/gstgldisplay.h
View file

@ -83,7 +83,7 @@ struct _GstGLDisplay
GstGLDisplayType type;
/*< protected >*/
GList *windows; /* OBJECT lock */
GList *windows; /* internal lock, use *_window functions instead */
GMainContext *main_context;
GMainLoop *main_loop;
GSource *event_source;