[mutter/wip/xtoglsync: 4/5] MetaSyncRing: disable after a number of reboot attempts

[Rui Matos <rtcm src gnome org>]

commit 24956fadcc41af45259f137be33be243edf5c3d4
Author: Rui Matos <tiagomatos gmail com>
Date:   Tue May 13 12:47:31 2014 +0200

    MetaSyncRing: disable after a number of reboot attempts
    
    If we have had to reboot this number of times, something is definitely
    wrong and we're likely to just make things worse by continuing to try.
    
    Let's err on the side of caution, disable ourselves and fallback to
    the XSync() path in the compositor.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=728464

 src/compositor/compositor.c     |    4 +-
 src/compositor/meta-sync-ring.c |   60 +++++++++++++++++++++++++++++++++-----
 src/compositor/meta-sync-ring.h |    4 +-
 3 files changed, 56 insertions(+), 12 deletions(-)
---
diff --git a/src/compositor/compositor.c b/src/compositor/compositor.c
index 42d3a0d..767016d 100644
--- a/src/compositor/compositor.c
+++ b/src/compositor/compositor.c
@@ -1193,7 +1193,7 @@ meta_pre_paint_func (gpointer data)
        * GLX buffers.
        */
       if (compositor->have_x11_sync_object)
-        meta_sync_ring_insert_wait ();
+        compositor->have_x11_sync_object = meta_sync_ring_insert_wait ();
       else
         XSync (compositor->display->xdisplay, False);
     }
@@ -1209,7 +1209,7 @@ meta_post_paint_func (gpointer data)
   if (compositor->frame_has_updated_xsurfaces)
     {
       if (compositor->have_x11_sync_object)
-        meta_sync_ring_after_frame ();
+        compositor->have_x11_sync_object = meta_sync_ring_after_frame ();
 
       compositor->frame_has_updated_xsurfaces = FALSE;
     }
diff --git a/src/compositor/meta-sync-ring.c b/src/compositor/meta-sync-ring.c
index c17c814..d29d13e 100644
--- a/src/compositor/meta-sync-ring.c
+++ b/src/compositor/meta-sync-ring.c
@@ -57,6 +57,7 @@
 
 #define NUM_SYNCS 10
 #define MAX_SYNC_WAIT_TIME (1 * 1000 * 1000 * 1000) /* one sec */
+#define MAX_REBOOT_ATTEMPTS 2
 
 typedef enum
 {
@@ -90,6 +91,8 @@ typedef struct
   guint current_sync_idx;
   MetaSync *current_sync;
   guint warmup_syncs;
+
+  guint reboots;
 } MetaSyncRing;
 
 static MetaSyncRing meta_sync_ring = { 0 };
@@ -115,6 +118,9 @@ static GLsync           (*meta_gl_import_sync) (GLenum external_sync_type,
 static MetaSyncRing *
 meta_sync_ring_get (void)
 {
+  if (meta_sync_ring.reboots > MAX_REBOOT_ATTEMPTS)
+    return NULL;
+
   return &meta_sync_ring;
 }
 
@@ -302,8 +308,13 @@ alarm_event_predicate (Display  *dpy,
                        XEvent   *event,
                        XPointer  data)
 {
+  int xsync_event_base;
   MetaSyncRing *ring = meta_sync_ring_get ();
-  int xsync_event_base = meta_display_get_sync_event_base (ring->display);
+
+  if (!ring)
+    return False;
+
+  xsync_event_base = meta_display_get_sync_event_base (ring->display);
 
   if (event->type == xsync_event_base + XSyncAlarmNotify)
     {
@@ -356,6 +367,9 @@ meta_sync_ring_init (MetaDisplay *display)
   guint i;
   MetaSyncRing *ring = meta_sync_ring_get ();
 
+  if (!ring)
+    return FALSE;
+
   g_return_val_if_fail (display != NULL, FALSE);
   g_return_val_if_fail (ring->display == NULL, FALSE);
 
@@ -392,6 +406,9 @@ meta_sync_ring_destroy (void)
   guint i;
   MetaSyncRing *ring = meta_sync_ring_get ();
 
+  if (!ring)
+    return;
+
   g_return_if_fail (ring->display != NULL);
 
   ring->current_sync_idx = 0;
@@ -406,18 +423,35 @@ meta_sync_ring_destroy (void)
   ring->display = NULL;
 }
 
-static void
+static gboolean
 meta_sync_ring_reboot (MetaDisplay *display)
 {
+  MetaSyncRing *ring = meta_sync_ring_get ();
+
+  if (!ring)
+    return FALSE;
+
   meta_sync_ring_destroy ();
-  meta_sync_ring_init (display);
+
+  ring->reboots += 1;
+
+  if (!meta_sync_ring_get ())
+    {
+      meta_warning ("MetaSyncRing: Too many reboots -- disabling\n");
+      return FALSE;
+    }
+
+  return meta_sync_ring_init (display);
 }
 
-void
+gboolean
 meta_sync_ring_after_frame (void)
 {
   MetaSyncRing *ring = meta_sync_ring_get ();
 
+  if (!ring)
+    return FALSE;
+
   g_return_if_fail (ring->display != NULL);
 
   if (ring->warmup_syncs >= NUM_SYNCS / 2)
@@ -435,8 +469,7 @@ meta_sync_ring_after_frame (void)
       if (status != GL_ALREADY_SIGNALED && status != GL_CONDITION_SATISFIED)
         {
           meta_warning ("MetaSyncRing: Timed out waiting for sync object.\n");
-          meta_sync_ring_reboot (ring->display);
-          return;
+          return meta_sync_ring_reboot (ring->display);
         }
 
       meta_sync_reset (sync_to_reset);
@@ -450,22 +483,30 @@ meta_sync_ring_after_frame (void)
   ring->current_sync_idx %= NUM_SYNCS;
 
   ring->current_sync = ring->syncs_array[ring->current_sync_idx];
+
+  return TRUE;
 }
 
-void
+gboolean
 meta_sync_ring_insert_wait (void)
 {
   MetaSyncRing *ring = meta_sync_ring_get ();
 
+  if (!ring)
+    return FALSE;
+
   g_return_if_fail (ring->display != NULL);
 
   if (ring->current_sync->state != META_SYNC_STATE_READY)
     {
       meta_warning ("MetaSyncRing: Sync object is not ready -- were events handled properly?\n");
-      meta_sync_ring_reboot (ring->display);
+      if (!meta_sync_ring_reboot (ring->display))
+        return FALSE;
     }
 
   meta_sync_insert (ring->current_sync);
+
+  return TRUE;
 }
 
 void
@@ -474,6 +515,9 @@ meta_sync_ring_handle_event (XSyncAlarmNotifyEvent *event)
   MetaSync *sync;
   MetaSyncRing *ring = meta_sync_ring_get ();
 
+  if (!ring)
+    return;
+
   g_return_if_fail (ring->display != NULL);
 
   sync = g_hash_table_lookup (ring->alarm_to_sync, (gpointer) event->alarm);
diff --git a/src/compositor/meta-sync-ring.h b/src/compositor/meta-sync-ring.h
index b0d2275..81d0aa0 100644
--- a/src/compositor/meta-sync-ring.h
+++ b/src/compositor/meta-sync-ring.h
@@ -10,8 +10,8 @@
 
 gboolean meta_sync_ring_init (MetaDisplay *dpy);
 void meta_sync_ring_destroy (void);
-void meta_sync_ring_after_frame (void);
-void meta_sync_ring_insert_wait (void);
+gboolean meta_sync_ring_after_frame (void);
+gboolean meta_sync_ring_insert_wait (void);
 void meta_sync_ring_handle_event (XSyncAlarmNotifyEvent *event);
 
 #endif  /* _META_SYNC_RING_H_ */