From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753221AbaAXPUq (ORCPT ); Fri, 24 Jan 2014 10:20:46 -0500 Received: from mga11.intel.com ([192.55.52.93]:7890 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752500AbaAXPUp (ORCPT ); Fri, 24 Jan 2014 10:20:45 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,713,1384329600"; d="scan'208";a="464172468" Subject: [linux-next][PATCH] mm: slub: work around unneeded lockdep warning To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Dave Hansen , peterz@infradead.org, penberg@kernel.org, linux@arm.linux.org.uk From: Dave Hansen Date: Fri, 24 Jan 2014 07:20:23 -0800 Message-Id: <20140124152023.A450E599@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I think this is a next-only thing. Pekka, can you pick this up, please? -- From: Dave Hansen 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. Signed-off-by: Dave Hansen Cc: Peter Zijlstra Cc: Pekka Enberg Cc: Russell King --- b/mm/slub.c | 6 ++++++ 1 file changed, 6 insertions(+) diff -puN mm/slub.c~slub-lockdep-workaround mm/slub.c --- a/mm/slub.c~slub-lockdep-workaround 2014-01-24 07:19:23.794069012 -0800 +++ b/mm/slub.c 2014-01-24 07:19:23.799069236 -0800 @@ -2890,7 +2890,13 @@ static void early_kmem_cache_node_alloc( 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) _