From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8BA81C43381 for ; Tue, 26 Mar 2019 05:04:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BA0E20823 for ; Tue, 26 Mar 2019 05:04:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730260AbfCZFEA (ORCPT ); Tue, 26 Mar 2019 01:04:00 -0400 Received: from orcrist.hmeau.com ([104.223.48.154]:59040 "EHLO deadmen.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725372AbfCZFEA (ORCPT ); Tue, 26 Mar 2019 01:04:00 -0400 Received: from gondobar.mordor.me.apana.org.au ([192.168.128.4] helo=gondobar) by deadmen.hmeau.com with esmtps (Exim 4.89 #2 (Debian)) id 1h8eFh-0004xj-Q7; Tue, 26 Mar 2019 13:03:57 +0800 Received: from herbert by gondobar with local (Exim 4.89) (envelope-from ) id 1h8eF6-0001xE-IO; Tue, 26 Mar 2019 13:03:20 +0800 Date: Tue, 26 Mar 2019 13:03:20 +0800 From: Herbert Xu To: NeilBrown Cc: Thomas Graf , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E. McKenney" Subject: Re: [PATCH 3/4] rhashtable: use bit_spin_locks to protect hash bucket. Message-ID: <20190326050320.gwk3tgtqwl5csivt@gondor.apana.org.au> References: <155349021177.1111.15681654355431465791.stgit@noble.brown> <155349033961.1111.18247269615646768227.stgit@noble.brown> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <155349033961.1111.18247269615646768227.stgit@noble.brown> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 25, 2019 at 04:05:39PM +1100, NeilBrown wrote: > > + * Sometimes we unlock a bucket by writing a new pointer there. In that > + * case we don't need to unlock, but we do need to reset state such as > + * local_bh. For that we have rht_unlocked(). This doesn't include > + * the memory barrier that bit_spin_unlock() provides, but rcu_assign_pointer() > + * will have provided that. Hmm, are you sure that's enough? IIRC rcu_assign_pointer only provides a write barrier compared to the more complete (but one-way) barrier that a spin-lock provides. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt