Fixes responsiveness for protocol shutdown.

When a protocol went down, all its routes were flushed in one step, that
may block BIRD for too much time. The patch fixes that by limiting
maximum number of routes flushed in one step.

1 files changed, 91 insertions, 34 deletions

diff --git a/nest/rt-table.c b/nest/rt-table.c
index 377687de..27adde16 100644
--- a/nest/rt-table.c
+++ b/nest/rt-table.c
@@ -55,7 +55,6 @@ static void rt_free_hostcache(rtable *tab);
 static void rt_notify_hostcache(rtable *tab, net *net);
 static void rt_update_hostcache(rtable *tab);
 static void rt_next_hop_update(rtable *tab);
-static void rt_prune(rtable *tab);
 
 static inline void rt_schedule_gc(rtable *tab);
 
@@ -838,6 +837,38 @@ rt_schedule_nhu(rtable *tab)
 }
 
 static void
+rt_prune_nets(rtable *tab)
+{
+  struct fib_iterator fit;
+  int ncnt = 0, ndel = 0;
+
+#ifdef DEBUGGING
+  fib_check(&tab->fib);
+#endif
+
+  FIB_ITERATE_INIT(&fit, &tab->fib);
+again:
+  FIB_ITERATE_START(&tab->fib, &fit, f)
+    {
+      net *n = (net *) f;
+      ncnt++;
+      if (!n->routes)		/* Orphaned FIB entry */
+	{
+	  FIB_ITERATE_PUT(&fit, f);
+	  fib_delete(&tab->fib, f);
+	  ndel++;
+	  goto again;
+	}
+    }
+  FIB_ITERATE_END(f);
+  DBG("Pruned %d of %d networks\n", ndel, ncnt);
+
+  tab->gc_counter = 0;
+  tab->gc_time = now;
+  tab->gc_scheduled = 0;
+}
+
+static void
 rt_event(void *ptr)
 {
   rtable *tab = ptr;
@@ -849,7 +880,7 @@ rt_event(void *ptr)
     rt_next_hop_update(tab);
 
   if (tab->gc_scheduled)
-    rt_prune(tab);
+    rt_prune_nets(tab);
 }
 
 void
@@ -885,70 +916,96 @@ rt_init(void)
   init_list(&routing_tables);
 }
 
-/**
- * rt_prune - prune a routing table
- * @tab: routing table to be pruned
- *
- * This function is called whenever a protocol shuts down. It scans
- * the routing table and removes all routes belonging to inactive
- * protocols and also stale network entries.
- */
-static void
-rt_prune(rtable *tab)
+
+/* Called from proto_schedule_flush_loop() only,
+   ensuring that all prune states are zero */
+void
+rt_schedule_prune_all(void)
 {
-  struct fib_iterator fit;
-  int rcnt = 0, rdel = 0, ncnt = 0, ndel = 0;
+  rtable *t;
+
+  WALK_LIST(t, routing_tables)
+    t->prune_state = 1;
+}
+
+static inline int
+rt_prune_step(rtable *tab, int *max_feed)
+{
+  struct fib_iterator *fit = &tab->prune_fit;
 
   DBG("Pruning route table %s\n", tab->name);
 #ifdef DEBUGGING
   fib_check(&tab->fib);
 #endif
-  FIB_ITERATE_INIT(&fit, &tab->fib);
+
+  if (tab->prune_state == 0)
+    return 1;
+
+  if (tab->prune_state == 1)
+    {
+      FIB_ITERATE_INIT(fit, &tab->fib);
+      tab->prune_state = 2;
+    }
+
 again:
-  FIB_ITERATE_START(&tab->fib, &fit, f)
+  FIB_ITERATE_START(&tab->fib, fit, fn)
     {
-      net *n = (net *) f;
+      net *n = (net *) fn;
       rte *e;
-      ncnt++;
+
     rescan:
-      for (e=n->routes; e; e=e->next, rcnt++)
+      for (e=n->routes; e; e=e->next)
 	if (e->sender->core_state != FS_HAPPY &&
 	    e->sender->core_state != FS_FEEDING)
 	  {
+	    if (*max_feed <= 0)
+	      {
+		FIB_ITERATE_PUT(fit, fn);
+		return 0;
+	      }
+
 	    rte_discard(tab, e);
-	    rdel++;
+	    (*max_feed)--;
+
 	    goto rescan;
 	  }
-      if (!n->routes)		/* Orphaned FIB entry? */
+      if (!n->routes)		/* Orphaned FIB entry */
 	{
-	  FIB_ITERATE_PUT(&fit, f);
-	  fib_delete(&tab->fib, f);
-	  ndel++;
+	  FIB_ITERATE_PUT(fit, fn);
+	  fib_delete(&tab->fib, fn);
 	  goto again;
 	}
     }
-  FIB_ITERATE_END(f);
-  DBG("Pruned %d of %d routes and %d of %d networks\n", rdel, rcnt, ndel, ncnt);
+  FIB_ITERATE_END(fn);
+
 #ifdef DEBUGGING
   fib_check(&tab->fib);
 #endif
-  tab->gc_counter = 0;
-  tab->gc_time = now;
-  tab->gc_scheduled = 0;
+
+  tab->prune_state = 0;
+  return 1;
 }
 
 /**
- * rt_prune_all - prune all routing tables
+ * rt_prune_loop - prune routing tables
+ * @tab: routing table to be pruned
  *
- * This function calls rt_prune() for all known routing tables.
+ * The prune loop scans routing tables and removes routes belonging to
+ * inactive protocols and also stale network entries. Returns 1 when
+ * all such routes are pruned. It is a part of the protocol flushing
+ * loop.
  */
-void
-rt_prune_all(void)
+int
+rt_prune_loop(void)
 {
   rtable *t;
+  int max_feed = 512;
 
   WALK_LIST(t, routing_tables)
-    rt_prune(t);
+    if (! rt_prune_step(t, &max_feed))
+      return 0;
+
+  return 1;
 }
 
 void