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glwindow/winrt: Add warning message if window is being closed from a UI thread

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All UI elements will follow Single-Threaded Apartments (STA) model.
As a result, we should access them from dedicated UI thread.
Due to the nature of the threading model, ANGLE will wait the UI
thread while closing internal window/swapchain objects.

A problem here is that when destroying GstGLWindow from the UI thread,
it will wait GstGLContext's internal thread. Meanwhile, the GstGLContext's
internal thread will be blocked because ANGLE wants to access the UI thread.
That will cause a deadlock or exceptions.

In short, application should not try to call
gst_element_set_state(pipeline, GST_STATE_NULL) from a UI thread.
That's a limitation of current implementation.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/745>
This commit is contained in:
Seungha Yang 2020-07-10 19:49:56 +09:00 committed by GStreamer Merge Bot
parent bdf73569f8
commit 579db691ed
1 changed files with 55 additions and 1 deletions
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56
gst-libs/gst/gl/winrt/gstglwindow_winrt_egl.cpp
View file

@ -331,6 +331,27 @@ public:
return false;
}
HRESULT
GetHasThreadAccess (bool &has_access)
{
HRESULT hr;
boolean val;
if (!isValid_ || !dispatcher_)
return E_FAIL;
hr = dispatcher_->get_HasThreadAccess (&val);
if (FAILED (hr))
return hr;
if (val)
has_access = true;
else
has_access = false;
return hr;
}
private:
bool
registerSizeChangedHandlerForCoreWindow (GstGLWindow * window)
@ -500,6 +521,7 @@ static guintptr gst_gl_window_winrt_egl_get_window_handle (GstGLWindow *
static void gst_gl_window_winrt_egl_set_window_handle (GstGLWindow * window,
guintptr handle);
static void gst_gl_window_winrt_egl_show (GstGLWindow * window);
static void gst_gl_window_winrt_egl_quit (GstGLWindow * window);
static void
gst_gl_window_winrt_egl_class_init (GstGLWindowWinRTEGLClass * klass)
@ -518,6 +540,8 @@ gst_gl_window_winrt_egl_class_init (GstGLWindowWinRTEGLClass * klass)
GST_DEBUG_FUNCPTR (gst_gl_window_winrt_egl_set_window_handle);
window_class->show =
GST_DEBUG_FUNCPTR (gst_gl_window_winrt_egl_show);
window_class->quit =
GST_DEBUG_FUNCPTR (gst_gl_window_winrt_egl_quit);
}
static void
@ -664,4 +688,34 @@ gst_gl_window_winrt_egl_on_resize (GstGLWindow * window,
g_mutex_unlock (&priv->event_lock);
gst_gl_window_resize (window, width, height);
}
}
static void
gst_gl_window_winrt_egl_quit (GstGLWindow * window)
{
GstGLWindowWinRTEGL *window_egl = GST_GL_WINDOW_WINRT_EGL (window);
GstGLWindowWinRTEGLPrivate *priv = window_egl->priv;
if (priv->resize_handler) {
HRESULT hr;
bool is_dispatcher_thread = false;
hr = priv->resize_handler->GetHasThreadAccess (is_dispatcher_thread);
if (SUCCEEDED (hr) && is_dispatcher_thread) {
/* In GstGLContext::destroy_context() -> eglDestroySurface(),
* ANGLE will wait a UI thread for its own operations to be called
* from the thread. Note that gst_gl_context_egl_destroy_context() will be
* called from GstGLContext's internal GL thread.
*
* A problem is that if GstGLWindow is being closed from the UI thread,
* ANGLE cannot access the UI thread as current thread is the thread.
*/
GST_ERROR_OBJECT (window,
"Closing from a UI thread might cause a deadlock or crash");
g_warning ("GstGLWindowWinRTEGL should be closed from non-UI thread");
}
}
GST_GL_WINDOW_CLASS (parent_class)->quit (window);
}