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gl/wayland: move roundtrip on show to window thread

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This makes it thread safe and fixes a possible deadlock.

Keeping the roundtrip off the window thread will result in two different
threads call wl_display_dispatch_queue() for the same queue which
violates the assumption for _dispatch_queue()'s thread-safety
guarantees.

https://bugzilla.gnome.org/show_bug.cgi?id=788754
https://bugzilla.gnome.org/show_bug.cgi?id=792156
https://bugzilla.gnome.org/show_bug.cgi?id=758984
This commit is contained in:
Matthew Waters 2018-01-04 15:33:33 +11:00
parent 384d27002c
commit b25413fb1c
2 changed files with 38 additions and 9 deletions
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16
gst-libs/gst/gl/wayland/gstglwindow_wayland_egl.c
View file

@ -292,8 +292,8 @@ create_surfaces (GstGLWindowWaylandEGL * window_egl)
wl_shell_get_shell_surface (display->shell,
window_egl->window.surface);
if (window_egl->window.queue)
wl_proxy_set_queue ((struct wl_proxy *) window_egl->window.
shell_surface, window_egl->window.queue);
wl_proxy_set_queue ((struct wl_proxy *) window_egl->
window.shell_surface, window_egl->window.queue);
wl_shell_surface_add_listener (window_egl->window.shell_surface,
&shell_surface_listener, window_egl);
@ -450,7 +450,7 @@ gst_gl_window_wayland_egl_set_window_handle (GstGLWindow * window,
}
static void
gst_gl_window_wayland_egl_show (GstGLWindow * window)
_roundtrip_async (GstGLWindow * window)
{
GstGLDisplayWayland *display_wayland =
GST_GL_DISPLAY_WAYLAND (window->display);
@ -463,6 +463,16 @@ gst_gl_window_wayland_egl_show (GstGLWindow * window)
GST_WARNING_OBJECT (window, "failed a roundtrip");
}
static void
gst_gl_window_wayland_egl_show (GstGLWindow * window)
{
GstGLWindowWaylandEGL *window_egl = GST_GL_WINDOW_WAYLAND_EGL (window);
create_surfaces (window_egl);
gst_gl_window_send_message (window, (GstGLWindowCB) _roundtrip_async, window);
}
static void
window_resize (GstGLWindowWaylandEGL * window_egl, guint width, guint height)
{

31
gst-libs/gst/gl/wayland/wayland_event_source.c
View file

@ -35,6 +35,7 @@
#include <stdint.h>
#include <stdlib.h>
#include <wayland-client.h>
#include <gst/gst.h>
#include "wayland_event_source.h"
@ -43,6 +44,8 @@ sync_callback (void *data, struct wl_callback *callback, uint32_t serial)
{
gboolean *done = data;
GST_TRACE ("roundtrip done. callback:%p", callback);
*done = TRUE;
wl_callback_destroy (callback);
}
@ -51,7 +54,14 @@ static const struct wl_callback_listener sync_listener = {
sync_callback
};
/* only thread safe iff called on the same thread @queue is being dispatched on */
/* only thread safe iff called on the same thread @queue is being dispatched on.
* Otherwise, two prepare_read{_queue}()'s can be indicated for the same
* queue and dispatch{_queue}() may be called for different threads which
* will cause deadlocks as no guarantees for thread-safety are given when
* pumping the same queue from multiple threads.
* As a concrete example, if the wayland event source (below) for a @queue is
* running on a certain thread, then this function must only be called in that
* thread (with that @queue). */
gint
gst_gl_wl_display_roundtrip_queue (struct wl_display *display,
struct wl_event_queue *queue)
@ -60,30 +70,38 @@ gst_gl_wl_display_roundtrip_queue (struct wl_display *display,
gboolean done = FALSE;
gint ret = 0;
GST_TRACE ("roundtrip start for dpy %p and queue %p", display, queue);
if (queue) {
/* creating a wl_proxy and setting the queue is racy with the dispatching
* of the default queue */
while (wl_display_prepare_read_queue (display, queue) != 0) {
if ((ret = wl_display_dispatch_queue_pending (display, queue)) < 0)
if ((ret = wl_display_dispatch_queue_pending (display, queue)) < 0) {
return ret;
}
}
}
if (!(callback = wl_display_sync (display))) {
return -1;
}
GST_TRACE ("create roundtrip callback %p", callback);
wl_callback_add_listener (callback, &sync_listener, &done);
if (queue) {
wl_proxy_set_queue ((struct wl_proxy *) callback, queue);
wl_display_cancel_read (display);
while (!done && ret >= 0)
while (!done && ret >= 0) {
ret = wl_display_dispatch_queue (display, queue);
}
} else {
while (!done && ret >= 0)
while (!done && ret >= 0) {
ret = wl_display_dispatch (display);
}
}
if (ret == -1 && !done)
wl_callback_destroy (callback);
GST_TRACE ("roundtrip done for dpy %p and queue %p. ret %i", display, queue,
ret);
return ret;
}
@ -156,10 +174,11 @@ wayland_event_source_dispatch (GSource * base,
{
WaylandEventSource *source = (WaylandEventSource *) base;
if (source->queue)
if (source->queue) {
wl_display_dispatch_queue_pending (source->display, source->queue);
else
} else {
wl_display_dispatch_pending (source->display);
}
source->pfd.revents = 0;
if (callback)