mm: slub: work around unneeded lockdep warning

The slub code does some setup during early boot in early_kmem_cache_node_alloc() with some local data. There is no possible way that another CPU can see this data, so the slub code doesn't unnecessarily lock it. However, some new lockdep asserts check to make sure that add_partial() _always_ has the list_lock held. Just add the locking, even though it is technically unnecessary. Cc: Peter Zijlstra <[email protected]> Cc: Russell King <[email protected]> Acked-by: David Rientjes <[email protected]> Signed-off-by: Dave Hansen <[email protected]> Signed-off-by: Pekka Enberg <[email protected]>
marineam · Jan 31, 2014 · 67b6c90 · 67b6c90
1 parent 433a91f
commit 67b6c90
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/mm/slub.c b/mm/slub.c
@@ -2890,7 +2890,13 @@ static void early_kmem_cache_node_alloc(int node)
 	init_kmem_cache_node(n);
 	inc_slabs_node(kmem_cache_node, node, page->objects);
 
+	/*
+	 * the lock is for lockdep's sake, not for any actual
+	 * race protection
+	 */
+	spin_lock(&n->list_lock);
 	add_partial(n, page, DEACTIVATE_TO_HEAD);
+	spin_unlock(&n->list_lock);
 }
 
 static void free_kmem_cache_nodes(struct kmem_cache *s)