backends/native: Fall back to compositing if direct scanout failed

Even when a direct client buffer has a compatible format, stride and
modifier for direct scanout, drmModePageFlip() may still fail sometimes.

From testing, it has been observed that it may seemingly randomly fail
with ENOSPC, where all subsequent attempts later on the same CRTC
failing with EBUSY.

Handle this by falling back to flipping after having composited a full
frame again.

Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1410

clutter/clutter/cogl/clutter-stage-cogl.c

@@ -649,10 +649,11 @@ clutter_stage_cogl_redraw_view_primary (ClutterStageCogl *stage_cogl,
   cairo_region_destroy (swap_region);
 }
 
-static void
+static gboolean
 clutter_stage_cogl_scanout_view (ClutterStageCogl  *stage_cogl,
                                  ClutterStageView  *view,
-                                 CoglScanout      *scanout)
+                                 CoglScanout       *scanout,
+                                 GError           **error)
 {
   ClutterStageCoglPrivate *priv =
     _clutter_stage_cogl_get_instance_private (stage_cogl);
@@ -660,14 +661,21 @@ clutter_stage_cogl_scanout_view (ClutterStageCogl *stage_cogl,
   CoglOnscreen *onscreen;
   CoglFrameInfo *frame_info;
 
-  g_return_if_fail (cogl_is_onscreen (framebuffer));
+  g_assert (cogl_is_onscreen (framebuffer));
 
   onscreen = COGL_ONSCREEN (framebuffer);
 
   frame_info = cogl_frame_info_new (priv->global_frame_counter);
+
+  if (!cogl_onscreen_direct_scanout (onscreen, scanout, frame_info, error))
+    {
+      cogl_object_unref (frame_info);
+      return FALSE;
+    }
+
   priv->global_frame_counter++;
 
-  cogl_onscreen_direct_scanout (onscreen, scanout, frame_info);
+  return TRUE;
 }
 
 static void
@@ -679,8 +687,15 @@ clutter_stage_cogl_redraw_view (ClutterStageWindow *stage_window,
 
   scanout = clutter_stage_view_take_scanout (view);
   if (scanout)
-    clutter_stage_cogl_scanout_view (stage_cogl, view, scanout);
+    {
-  else
+      g_autoptr (GError) error = NULL;
+
+      if (clutter_stage_cogl_scanout_view (stage_cogl, view, scanout, &error))
+        return;
+
+      g_warning ("Failed to scan out client buffer: %s", error->message);
+    }
+
   clutter_stage_cogl_redraw_view_primary (stage_cogl, view);
 }
 

cogl/cogl/cogl-onscreen.c

@@ -406,24 +406,30 @@ cogl_onscreen_get_buffer_age (CoglOnscreen *onscreen)
   return winsys->onscreen_get_buffer_age (onscreen);
 }
 
-void
+gboolean
 cogl_onscreen_direct_scanout (CoglOnscreen   *onscreen,
                               CoglScanout    *scanout,
-                              CoglFrameInfo *info)
+                              CoglFrameInfo  *info,
+                              GError        **error)
 {
   CoglFramebuffer *framebuffer = COGL_FRAMEBUFFER (onscreen);
   const CoglWinsysVtable *winsys;
 
-  g_return_if_fail (framebuffer->type == COGL_FRAMEBUFFER_TYPE_ONSCREEN);
+  g_warn_if_fail (framebuffer->type == COGL_FRAMEBUFFER_TYPE_ONSCREEN);
-  g_return_if_fail (_cogl_winsys_has_feature (COGL_WINSYS_FEATURE_SYNC_AND_COMPLETE_EVENT));
+  g_warn_if_fail (_cogl_winsys_has_feature (COGL_WINSYS_FEATURE_SYNC_AND_COMPLETE_EVENT));
 
   info->frame_counter = onscreen->frame_counter;
   g_queue_push_tail (&onscreen->pending_frame_infos, info);
 
   winsys = _cogl_framebuffer_get_winsys (framebuffer);
-  winsys->onscreen_direct_scanout (onscreen, scanout, info);
+  if (!winsys->onscreen_direct_scanout (onscreen, scanout, info, error))
+    {
+      g_queue_pop_tail (&onscreen->pending_frame_infos);
+      return FALSE;
+    }
 
   onscreen->frame_counter++;
+  return TRUE;
 }
 
 #ifdef COGL_HAS_X11_SUPPORT

cogl/cogl/cogl-onscreen.h

@@ -291,10 +291,11 @@ cogl_onscreen_swap_buffers_with_damage (CoglOnscreen *onscreen,
 /**
  * cogl_onscreen_direct_scanout: (skip)
  */
-COGL_EXPORT void
+COGL_EXPORT gboolean
 cogl_onscreen_direct_scanout (CoglOnscreen   *onscreen,
                               CoglScanout    *scanout,
-                              CoglFrameInfo *info);
+                              CoglFrameInfo  *info,
+                              GError        **error);
 
 /**
  * cogl_onscreen_swap_region:

cogl/cogl/winsys/cogl-winsys-private.h

@@ -119,10 +119,11 @@ typedef struct _CoglWinsysVtable
                                         int n_rectangles,
                                         CoglFrameInfo *info);
 
-  void
+  gboolean
   (*onscreen_direct_scanout) (CoglOnscreen   *onscreen,
                               CoglScanout    *scanout,
-                              CoglFrameInfo *info);
+                              CoglFrameInfo  *info,
+                              GError        **error);
 
   void
   (*onscreen_set_visibility) (CoglOnscreen *onscreen,

src/backends/native/meta-crtc-kms.c

@@ -206,12 +206,14 @@ meta_crtc_kms_set_mode (MetaCrtcKms   *crtc_kms,
 void
 meta_crtc_kms_page_flip (MetaCrtcKms                   *crtc_kms,
                          const MetaKmsPageFlipFeedback *page_flip_feedback,
+                         MetaKmsPageFlipFlag            flags,
                          gpointer                       user_data,
                          MetaKmsUpdate                 *kms_update)
 {
   meta_kms_update_page_flip (kms_update,
                              meta_crtc_kms_get_kms_crtc (crtc_kms),
                              page_flip_feedback,
+                             flags,
                              user_data);
 }
 

src/backends/native/meta-crtc-kms.h

@@ -30,6 +30,7 @@
 #include "backends/meta-crtc.h"
 #include "backends/native/meta-gpu-kms.h"
 #include "backends/native/meta-kms-crtc.h"
+#include "backends/native/meta-kms-update.h"
 
 #define META_TYPE_CRTC_KMS (meta_crtc_kms_get_type ())
 G_DECLARE_FINAL_TYPE (MetaCrtcKms, meta_crtc_kms,
@@ -56,6 +57,7 @@ void meta_crtc_kms_set_mode (MetaCrtcKms   *crtc_kms,
 
 void meta_crtc_kms_page_flip (MetaCrtcKms                   *crtc_kms,
                               const MetaKmsPageFlipFeedback *page_flip_feedback,
+                              MetaKmsPageFlipFlag            flags,
                               gpointer                       user_data,
                               MetaKmsUpdate                 *kms_update);
 

src/backends/native/meta-kms-impl-simple.c

@@ -988,6 +988,9 @@ err_planes_assigned:
     {
       MetaKmsPageFlip *page_flip = l->data;
 
+      if (page_flip->flags & META_KMS_PAGE_FLIP_FLAG_NO_DISCARD_FEEDBACK)
+        continue;
+
       discard_page_flip (impl, update, page_flip);
     }
 

src/backends/native/meta-kms-update-private.h

@@ -87,6 +87,7 @@ typedef struct _MetaKmsPageFlip
 {
   MetaKmsCrtc *crtc;
   const MetaKmsPageFlipFeedback *feedback;
+  MetaKmsPageFlipFlag flags;
   gpointer user_data;
   MetaKmsCustomPageFlipFunc custom_page_flip_func;
   gpointer custom_page_flip_user_data;

src/backends/native/meta-kms-update.c

@@ -285,6 +285,7 @@ void
 meta_kms_update_page_flip (MetaKmsUpdate                 *update,
                            MetaKmsCrtc                   *crtc,
                            const MetaKmsPageFlipFeedback *feedback,
+                           MetaKmsPageFlipFlag            flags,
                            gpointer                       user_data)
 {
   MetaKmsPageFlip *page_flip;
@@ -295,6 +296,7 @@ meta_kms_update_page_flip (MetaKmsUpdate                 *update,
   *page_flip = (MetaKmsPageFlip) {
     .crtc = crtc,
     .feedback = feedback,
+    .flags = flags,
     .user_data = user_data,
   };
 

src/backends/native/meta-kms-update.h

@@ -41,6 +41,12 @@ typedef enum _MetaKmsAssignPlaneFlag
   META_KMS_ASSIGN_PLANE_FLAG_FB_UNCHANGED = 1 << 0,
 } MetaKmsAssignPlaneFlag;
 
+typedef enum _MetaKmsPageFlipFlag
+{
+  META_KMS_PAGE_FLIP_FLAG_NONE = 0,
+  META_KMS_PAGE_FLIP_FLAG_NO_DISCARD_FEEDBACK = 1 << 0,
+} MetaKmsPageFlipFlag;
+
 struct _MetaKmsPageFlipFeedback
 {
   void (* flipped) (MetaKmsCrtc  *crtc,
@@ -99,6 +105,7 @@ MetaKmsPlaneAssignment * meta_kms_update_unassign_plane (MetaKmsUpdate *update,
 void meta_kms_update_page_flip (MetaKmsUpdate                 *update,
                                 MetaKmsCrtc                   *crtc,
                                 const MetaKmsPageFlipFeedback *feedback,
+                                MetaKmsPageFlipFlag            flags,
                                 gpointer                       user_data);
 
 void meta_kms_update_custom_page_flip (MetaKmsUpdate                 *update,

src/backends/native/meta-renderer-native.c

@@ -1254,6 +1254,7 @@ static void
 meta_onscreen_native_flip_crtc (CoglOnscreen        *onscreen,
                                 MetaRendererView    *view,
                                 MetaCrtc            *crtc,
+                                MetaKmsPageFlipFlag  flags,
                                 MetaKmsUpdate       *kms_update)
 {
   CoglOnscreenEGL *onscreen_egl = onscreen->winsys;
@@ -1288,6 +1289,7 @@ meta_onscreen_native_flip_crtc (CoglOnscreen     *onscreen,
       meta_crtc_kms_assign_primary_plane (crtc_kms, fb_id, kms_update);
       meta_crtc_kms_page_flip (crtc_kms,
                                &page_flip_feedback,
+                               flags,
                                g_object_ref (view),
                                kms_update);
 
@@ -1341,6 +1343,7 @@ meta_onscreen_native_set_crtc_mode (CoglOnscreen              *onscreen,
 
 static void
 meta_onscreen_native_flip_crtcs (CoglOnscreen        *onscreen,
+                                 MetaKmsPageFlipFlag  flags,
                                  MetaKmsUpdate       *kms_update)
 {
   CoglOnscreenEGL *onscreen_egl = onscreen->winsys;
@@ -1359,6 +1362,7 @@ meta_onscreen_native_flip_crtcs (CoglOnscreen  *onscreen,
   if (power_save_mode == META_POWER_SAVE_ON)
     {
       meta_onscreen_native_flip_crtc (onscreen, view, onscreen_native->crtc,
+                                      flags,
                                       kms_update);
     }
   else
@@ -1925,7 +1929,9 @@ meta_onscreen_native_swap_buffers_with_damage (CoglOnscreen  *onscreen,
   update_secondary_gpu_state_post_swap_buffers (onscreen, &egl_context_changed);
 
   ensure_crtc_modes (onscreen, kms_update);
-  meta_onscreen_native_flip_crtcs (onscreen, kms_update);
+  meta_onscreen_native_flip_crtcs (onscreen,
+                                   META_KMS_PAGE_FLIP_FLAG_NONE,
+                                   kms_update);
 
   /*
    * If we changed EGL context, cogl will have the wrong idea about what is
@@ -2072,10 +2078,11 @@ meta_onscreen_native_is_buffer_scanout_compatible (CoglOnscreen *onscreen,
   return TRUE;
 }
 
-static void
+static gboolean
 meta_onscreen_native_direct_scanout (CoglOnscreen   *onscreen,
                                      CoglScanout    *scanout,
-                                     CoglFrameInfo *frame_info)
+                                     CoglFrameInfo  *frame_info,
+                                     GError        **error)
 {
   CoglOnscreenEGL *onscreen_egl = onscreen->winsys;
   MetaOnscreenNative *onscreen_native = onscreen_egl->platform;
@@ -2090,21 +2097,38 @@ meta_onscreen_native_direct_scanout (CoglOnscreen  *onscreen,
   MetaBackendNative *backend_native = META_BACKEND_NATIVE (backend);
   MetaKms *kms = meta_backend_native_get_kms (backend_native);
   MetaKmsUpdate *kms_update;
+  g_autoptr (MetaKmsFeedback) kms_feedback = NULL;
 
   kms_update = meta_kms_ensure_pending_update (kms);
 
   renderer_gpu_data = meta_renderer_native_get_gpu_data (renderer_native,
                                                          render_gpu);
 
-  g_return_if_fail (renderer_gpu_data->mode == META_RENDERER_NATIVE_MODE_GBM);
+  g_warn_if_fail (renderer_gpu_data->mode == META_RENDERER_NATIVE_MODE_GBM);
-
   g_warn_if_fail (!onscreen_native->gbm.next_fb);
+
   g_set_object (&onscreen_native->gbm.next_fb, META_DRM_BUFFER (scanout));
 
   ensure_crtc_modes (onscreen, kms_update);
-  meta_onscreen_native_flip_crtcs (onscreen, kms_update);
+  meta_onscreen_native_flip_crtcs (onscreen,
+                                   META_KMS_PAGE_FLIP_FLAG_NO_DISCARD_FEEDBACK,
+                                   kms_update);
 
-  meta_kms_post_pending_update_sync (kms);
+  kms_feedback = meta_kms_post_pending_update_sync (kms);
+  if (meta_kms_feedback_get_result (kms_feedback) != META_KMS_FEEDBACK_PASSED)
+    {
+      const GError *feedback_error = meta_kms_feedback_get_error (kms_feedback);
+
+      if (g_error_matches (feedback_error,
+                           G_IO_ERROR, G_IO_ERROR_PERMISSION_DENIED))
+        return TRUE;
+
+      g_clear_object (&onscreen_native->gbm.next_fb);
+      g_propagate_error (error, g_error_copy (feedback_error));
+      return FALSE;
+    }
+
+  return TRUE;
 }
 
 static gboolean