backend-drm: fix race during system suspend

Depending on system loading, weston-launcher could drop the drm
master access before the compositor and all the clients receive
the notification. In this case, some commit could be sent to the
drm driver too late and get refused with error EACCES.
This error condition is not properly managed and causes weston to
hang.

Change the return type of start_repaint_loop() and repaint_flush()
from void to int, and return 0 on success or -1 if the repaint has
to be cancelled.
In the callers of start_repaint_loop() and repaint_flush() handle
the return value and cancel the repaint when needed.
In backend-drm detect the error EACCES and return -1.
Note: to keep the code cleaner, this change inverts the execution
order between weston_output_schedule_repaint_reset() and
repaint_cancel().

No need to wait for suspend or for any notification; in case the
weston reschedules a repaint, it will get EACCES again.
At resume, damage-all guarantees a complete repaint.

This fix is for atomic modeset only.
Legacy modeset suffers from similar problems, but it is not fixed
by this change. Since drm_pending_state_apply() never returns
error for legacy modeset, this change has no impact on legacy
modeset.

Signed-off-by: Antonio Borneo <antonio.borneo@st.com>
Fixes: https://gitlab.freedesktop.org/wayland/weston/issues/117

include/libweston/libweston.h

@@ -301,7 +301,7 @@ struct weston_output {
 	enum weston_hdcp_protection current_protection;
 	bool allow_protection;
 
-	void (*start_repaint_loop)(struct weston_output *output);
+	int (*start_repaint_loop)(struct weston_output *output);
 	int (*repaint)(struct weston_output *output,
 			pixman_region32_t *damage,
 			void *repaint_data);
@@ -1053,7 +1053,7 @@ struct weston_backend {
 	 *
 	 * @param repaint_data Data returned by repaint_begin
 	 */
-	void (*repaint_flush)(struct weston_compositor *compositor,
+	int (*repaint_flush)(struct weston_compositor *compositor,
 			     void *repaint_data);
 
 	/** Allocate a new output

libweston/backend-drm/drm.c

@@ -463,7 +463,7 @@ drm_waitvblank_pipe(struct drm_output *output)
 		return 0;
 }
 
-static void
+static int
 drm_output_start_repaint_loop(struct weston_output *output_base)
 {
 	struct drm_output *output = to_drm_output(output_base);
@@ -482,7 +482,7 @@ drm_output_start_repaint_loop(struct weston_output *output_base)
 	};
 
 	if (output->disable_pending || output->destroy_pending)
-		return;
+		return 0;
 
 	if (!output->scanout_plane->state_cur->fb) {
 		/* We can't page flip if there's no mode set */
@@ -519,7 +519,7 @@ drm_output_start_repaint_loop(struct weston_output *output_base)
 			drm_output_update_msc(output, vbl.reply.sequence);
 			weston_output_finish_frame(output_base, &ts,
 						WP_PRESENTATION_FEEDBACK_INVALID);
-			return;
+			return 0;
 		}
 	}
 
@@ -538,15 +538,18 @@ drm_output_start_repaint_loop(struct weston_output *output_base)
 	if (ret != 0) {
 		weston_log("applying repaint-start state failed: %s\n",
 			   strerror(errno));
+		if (ret == -EACCES)
+			return -1;
 		goto finish_frame;
 	}
 
-	return;
+	return 0;
 
 finish_frame:
 	/* if we cannot page-flip, immediately finish frame */
 	weston_output_finish_frame(output_base, NULL,
 				   WP_PRESENTATION_FEEDBACK_INVALID);
+	return 0;
 }
 
 /**
@@ -585,15 +588,21 @@ drm_repaint_begin(struct weston_compositor *compositor)
  * the update completes (see drm_output_update_complete), the output
  * state will be freed.
  */
-static void
+static int
 drm_repaint_flush(struct weston_compositor *compositor, void *repaint_data)
 {
 	struct drm_backend *b = to_drm_backend(compositor);
 	struct drm_pending_state *pending_state = repaint_data;
+	int ret;
+
+	ret = drm_pending_state_apply(pending_state);
+	if (ret != 0)
+		weston_log("repaint-flush failed: %s\n", strerror(errno));
 
-	drm_pending_state_apply(pending_state);
 	drm_debug(b, "[repaint] flushed pending_state %p\n", pending_state);
 	b->repaint_data = NULL;
+
+	return (ret == -EACCES) ? -1 : 0;
 }
 
 /**
@@ -2928,11 +2937,13 @@ renderer_switch_binding(struct weston_keyboard *keyboard,
 	switch_to_gl_renderer(b);
 }
 
-static void
+static int
 drm_virtual_output_start_repaint_loop(struct weston_output *output_base)
 {
 	weston_output_finish_frame(output_base, NULL,
 				   WP_PRESENTATION_FEEDBACK_INVALID);
+
+	return 0;
 }
 
 static int

libweston/backend-fbdev/fbdev.c

@@ -131,13 +131,15 @@ fbdev_output_get_head(struct fbdev_output *output)
 			    struct fbdev_head, base.output_link);
 }
 
-static void
+static int
 fbdev_output_start_repaint_loop(struct weston_output *output)
 {
 	struct timespec ts;
 
 	weston_compositor_read_presentation_clock(output->compositor, &ts);
 	weston_output_finish_frame(output, &ts, WP_PRESENTATION_FEEDBACK_INVALID);
+
+	return 0;
 }
 
 static int

libweston/backend-headless/headless.c

@@ -80,13 +80,15 @@ to_headless_backend(struct weston_compositor *base)
 	return container_of(base->backend, struct headless_backend, base);
 }
 
-static void
+static int
 headless_output_start_repaint_loop(struct weston_output *output)
 {
 	struct timespec ts;
 
 	weston_compositor_read_presentation_clock(output->compositor, &ts);
 	weston_output_finish_frame(output, &ts, WP_PRESENTATION_FEEDBACK_INVALID);
+
+	return 0;
 }
 
 static int

libweston/backend-rdp/rdp.c

@@ -382,13 +382,15 @@ rdp_peer_refresh_region(pixman_region32_t *region, freerdp_peer *peer)
 		rdp_peer_refresh_raw(region, output->shadow_surface, peer);
 }
 
-static void
+static int
 rdp_output_start_repaint_loop(struct weston_output *output)
 {
 	struct timespec ts;
 
 	weston_compositor_read_presentation_clock(output->compositor, &ts);
 	weston_output_finish_frame(output, &ts, WP_PRESENTATION_FEEDBACK_INVALID);
+
+	return 0;
 }
 
 static int

libweston/backend-wayland/wayland.c

@@ -481,7 +481,7 @@ wayland_output_update_gl_border(struct wayland_output *output)
 }
 #endif
 
-static void
+static int
 wayland_output_start_repaint_loop(struct weston_output *output_base)
 {
 	struct wayland_output *output = to_wayland_output(output_base);
@@ -503,6 +503,8 @@ wayland_output_start_repaint_loop(struct weston_output *output_base)
 	wl_callback_add_listener(output->frame_cb, &frame_listener, output);
 	wl_surface_commit(output->parent.surface);
 	wl_display_flush(wb->parent.wl_display);
+
+	return 0;
 }
 
 #ifdef ENABLE_EGL

libweston/backend-x11/x11.c

@@ -399,13 +399,15 @@ x11_input_destroy(struct x11_backend *b)
 	weston_seat_release(&b->core_seat);
 }
 
-static void
+static int
 x11_output_start_repaint_loop(struct weston_output *output)
 {
 	struct timespec ts;
 
 	weston_compositor_read_presentation_clock(output->compositor, &ts);
 	weston_output_finish_frame(output, &ts, WP_PRESENTATION_FEEDBACK_INVALID);
+
+	return 0;
 }
 
 static int

libweston/compositor.c

@@ -2790,17 +2790,19 @@ output_repaint_timer_handler(void *data)
 
 	if (ret == 0) {
 		if (compositor->backend->repaint_flush)
-			compositor->backend->repaint_flush(compositor,
+			ret = compositor->backend->repaint_flush(compositor,
 							 repaint_data);
 	} else {
+		if (compositor->backend->repaint_cancel)
+			compositor->backend->repaint_cancel(compositor,
+							    repaint_data);
+	}
+
+	if (ret != 0) {
 		wl_list_for_each(output, &compositor->output_list, link) {
 			if (output->repainted)
 				weston_output_schedule_repaint_reset(output);
 		}
-
-		if (compositor->backend->repaint_cancel)
-			compositor->backend->repaint_cancel(compositor,
-							    repaint_data);
 	}
 
 	wl_list_for_each(output, &compositor->output_list, link)
@@ -2887,11 +2889,14 @@ static void
 idle_repaint(void *data)
 {
 	struct weston_output *output = data;
+	int ret;
 
 	assert(output->repaint_status == REPAINT_BEGIN_FROM_IDLE);
 	output->repaint_status = REPAINT_AWAITING_COMPLETION;
 	output->idle_repaint_source = NULL;
-	output->start_repaint_loop(output);
+	ret = output->start_repaint_loop(output);
+	if (ret != 0)
+		weston_output_schedule_repaint_reset(output);
 }
 
 WL_EXPORT void

remoting/remoting-plugin.c

@@ -93,7 +93,7 @@ struct remoted_output {
 	void (*saved_destroy)(struct weston_output *output);
 	int (*saved_enable)(struct weston_output *output);
 	int (*saved_disable)(struct weston_output *output);
-	void (*saved_start_repaint_loop)(struct weston_output *output);
+	int (*saved_start_repaint_loop)(struct weston_output *output);
 
 	char *host;
 	int port;
@@ -647,7 +647,7 @@ remoting_output_destroy(struct weston_output *output)
 	free(remoted_output);
 }
 
-static void
+static int
 remoting_output_start_repaint_loop(struct weston_output *output)
 {
 	struct remoted_output *remoted_output = lookup_remoted_output(output);
@@ -658,6 +658,8 @@ remoting_output_start_repaint_loop(struct weston_output *output)
 	msec = millihz_to_nsec(remoted_output->output->current_mode->refresh)
 			/ 1000000;
 	wl_event_source_timer_update(remoted_output->finish_frame_timer, msec);
+
+	return 0;
 }
 
 static int