Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753096AbbLSEnG (ORCPT ); Fri, 18 Dec 2015 23:43:06 -0500 Received: from shards.monkeyblade.net ([149.20.54.216]:53139 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752196AbbLSEnE (ORCPT ); Fri, 18 Dec 2015 23:43:04 -0500 Date: Fri, 18 Dec 2015 23:42:59 -0500 (EST) Message-Id: <20151218.234259.445944618583370177.davem@davemloft.net> To: herbert@gondor.apana.org.au Cc: eric.dumazet@gmail.com, ying.huang@linux.intel.com, lkp@01.org, linux-kernel@vger.kernel.org, colin.king@canonical.com, fengguang.wu@intel.com, netdev@vger.kernel.org Subject: Re: [PATCH v2] rhashtable: Kill harmless RCU warning in rhashtable_walk_init From: David Miller In-Reply-To: <20151219024528.GA27814@gondor.apana.org.au> References: <20151218131408.GA21756@gondor.apana.org.au> <20151218.162731.305092674804556753.davem@davemloft.net> <20151219024528.GA27814@gondor.apana.org.au> X-Mailer: Mew version 6.7 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Fri, 18 Dec 2015 20:43:03 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1801 Lines: 53 From: Herbert Xu Date: Sat, 19 Dec 2015 10:45:28 +0800 > On Fri, Dec 18, 2015 at 04:27:31PM -0500, David Miller wrote: >> From: Herbert Xu >> Date: Fri, 18 Dec 2015 21:14:08 +0800 >> >> > On Fri, Dec 18, 2015 at 04:54:14AM -0800, Eric Dumazet wrote: >> >> >> >> You can avoid the comment by using the self documented and lockdep >> >> enabled primitive >> >> >> >> iter->walker->tbl = rcu_dereference_protected(ht->tbl, >> >> lockdep_is_held(&ht->lock)); >> > >> > That is just gross. I think a comment is much better in this case. >> >> Herbert, this macro was created exactly to handle this situation, >> and this is what we do everywhere else in the tree. > > OK. > > ---8<--- > The commit f9f51b8070be3e829100614a7372b219723b864f ("rhashtable: > Fix walker list corruption") causes a suspicious RCU usage warning > because we no longer hold ht->mutex when we dereference ht->tbl. > > However, this is a false positive because we now hold ht->lock > which also guarantees that ht->tbl won't disppear from under us. > > This patch kills the warning by using rcu_dereference_protected. > > Reported-by: kernel test robot > Signed-off-by: Herbert Xu The correct commti SHA1 is c6ff5268293ef98e48a99597e765ffc417e39fa5. Or at least, when I run: git show f9f51b8070be3e829100614a7372b219723b864f I get: fatal: bad object f9f51b8070be3e829100614a7372b219723b864f :-) I fixed this up and applied this, thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/