From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932764Ab1KGQWI (ORCPT ); Mon, 7 Nov 2011 11:22:08 -0500 Received: from mail-qy0-f174.google.com ([209.85.216.174]:52857 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932651Ab1KGQWG (ORCPT ); Mon, 7 Nov 2011 11:22:06 -0500 Date: Mon, 7 Nov 2011 08:21:59 -0800 From: Tejun Heo To: Peter Zijlstra Cc: Vegard Nossum , Yong Zhang , linux-kernel@vger.kernel.org, sergey.senozhatsky@gmail.com, bp@alien8.de, Ingo Molnar , David Rientjes , casteyde.christian@free.fr Subject: Re: [PATCH 1/4] lockdep: lock_set_subclass() fix Message-ID: <20111107162159.GC13699@google.com> References: <1320398790-21663-1-git-send-email-yong.zhang0@gmail.com> <1320398790-21663-2-git-send-email-yong.zhang0@gmail.com> <1320669279.18053.29.camel@twins> <1320682230.17809.11.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1320682230.17809.11.camel@twins> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, Nov 07, 2011 at 05:10:29PM +0100, Peter Zijlstra wrote: > We could move the key and name pointer to the start of the structure and > memset everything after that, however wouldn't that leave kmemcheck with > the same problem? It wouldn't know those two pointers would be > initialized properly. At that point, lockdep_map is guaranteed to have passed through lockdep_init_map(), so I think it should be fine. > @@ -148,9 +148,9 @@ void clear_lock_stats(struct lock_class *class); > * This is embedded into specific lock instances: > */ > struct lockdep_map { > + const char *name; > struct lock_class_key *key; > struct lock_class *class_cache[NR_LOCKDEP_CACHING_CLASSES]; > - const char *name; > #ifdef CONFIG_LOCK_STAT > int cpu; > unsigned long ip; Probably fat comment explaining the ordering requirement here w/ #define LOCKDEP_MAP_INIT_OFFSET offsetof(struct lockdep_map, class_cache) > diff --git a/kernel/lockdep.c b/kernel/lockdep.c > index e69434b..81855cf 100644 > --- a/kernel/lockdep.c > +++ b/kernel/lockdep.c > @@ -2948,7 +2948,8 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this, > void lockdep_init_map(struct lockdep_map *lock, const char *name, > struct lock_class_key *key, int subclass) > { > - memset(lock, 0, sizeof(*lock)); > + kmemcheck_mark_initialized(lock, 2*sizeof(void *)); > + memset(&lock->class_cache[0], 0, sizeof(*lock)-2*sizeof(void *)); And something like the following? memset((void *)lock + LOCKDEP_MAP_INIT_OFFSET, 0, sizeof(*lock) - LOCKDEP_MAP_INIT_OFFSET); Thanks. -- tejun