Table: RCU synchronization moved to lfjour

the sync is actually needed when the pages get freed, not precisely
after every item cleanup, as the data technically stays intact until the
deferred free's are called.

lib/lockfree.c

@@ -359,10 +359,6 @@ lfjour_cleanup_hook(void *_j)
   {
     j->item_done(j, first);
 
-#ifdef LOCAL_DEBUG
-    memset(first, 0xbd, j->item_size);
-#endif
-
     /* Find next journal item */
     struct lfjour_item *next = lfjour_get_next(j, first);
     if (PAGE_HEAD(next) != PAGE_HEAD(first))
@@ -374,6 +370,11 @@ lfjour_cleanup_hook(void *_j)
 
       /* Free this block */
       lfjour_block_rem_node(&j->pending, block);
+
+      /* Wait for possible pending readers of the block */
+      synchronize_rcu();
+
+      /* Now we can finally drop the block */
 #ifdef LOCAL_DEBUG
       memset(block, 0xbe, page_size);
 #endif

nest/rt-table.c

@@ -1503,9 +1503,6 @@ rt_cleanup_export_best(struct lfjour *j, struct lfjour_item *i)
 
   /* Update the first and last pointers */
   rt_cleanup_update_pointers(&net->best, rpe);
-
-  /* Wait for readers before releasing */
-  synchronize_rcu();
 }
 
 static void
@@ -1530,9 +1527,6 @@ rt_cleanup_export_all(struct lfjour *j, struct lfjour_item *i)
 
   if (is_last)
     tab->gc_counter++;
-
-  /* Wait for readers before releasing */
-  synchronize_rcu();
 }
 
 static void