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=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 6930DC433E1 for ; Thu, 13 Aug 2020 07:31:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DC4120771 for ; Thu, 13 Aug 2020 07:31:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="YGeTingr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726072AbgHMHbU (ORCPT ); Thu, 13 Aug 2020 03:31:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726044AbgHMHbU (ORCPT ); Thu, 13 Aug 2020 03:31:20 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 291BCC061757; Thu, 13 Aug 2020 00:31:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ajCb1YweODRt8vtNgU7fmlorkYYs90KZ1F0rpuEPtl0=; b=YGeTingr3glZ1JMMusE7MilLak YI89fMIo2FLGBSdXX9JYBIDTA+JBbbgemHrKTM51+e4gaqUgQylwW6Ii779fE0k0948daKKAI2mHL t6r3HKOoxdEUctwqjLGL0tdfqoa1zbfNg5gLflFt+6j9xBojWz9Eaz8PAi7S78FTGfU/1j4oNnq4j jFnAjhC3driUp+OJ9ybAced0njDwxF8UujHre2BD53vEGAPhtJZqMWIfGGbF4rNFMkJOT3HsZOoUZ 5COFx/sIkzxvnttM7QEXRjlJ2bEI+Q+z0ic/BFsDL9J0FrBmIiXW/E1Q5beEsiq+UsD4e+wyQ1w4r JIfVgb4A==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1k67hj-00049n-W6; Thu, 13 Aug 2020 07:31:16 +0000 Date: Thu, 13 Aug 2020 08:31:15 +0100 From: Christoph Hellwig To: Jacob Wen Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: [PATCH] block: insert a general SMP memory barrier before wake_up_bit() Message-ID: <20200813073115.GA15436@infradead.org> References: <20200813024438.13170-1-jian.w.wen@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200813024438.13170-1-jian.w.wen@oracle.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Thu, Aug 13, 2020 at 10:44:38AM +0800, Jacob Wen wrote: > wake_up_bit() uses waitqueue_active() that needs the explicit smp_mb(). Sounds like the barrier should go into wake_up_bit then.. > > Signed-off-by: Jacob Wen > --- > fs/block_dev.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 0ae656e022fd..e74980848a2a 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -1175,6 +1175,7 @@ static void bd_clear_claiming(struct block_device *whole, void *holder) > /* tell others that we're done */ > BUG_ON(whole->bd_claiming != holder); > whole->bd_claiming = NULL; > + smp_mb(); > wake_up_bit(&whole->bd_claiming, 0); > } > > -- > 2.17.1 > ---end quoted text---