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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E37F8C43603 for ; Wed, 4 Dec 2019 15:29:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B4C4C207DD for ; Wed, 4 Dec 2019 15:29:00 +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="VvlqX/hs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728442AbfLDP27 (ORCPT ); Wed, 4 Dec 2019 10:28:59 -0500 Received: from merlin.infradead.org ([205.233.59.134]:33826 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728209AbfLDP27 (ORCPT ); Wed, 4 Dec 2019 10:28:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=h87ip3hGwhH4oIF/zayIPJ2ZwZuEoxtcahchs45r+eM=; b=VvlqX/hslMRwwQbo/hbpVXpeE fFlwFikcGnyw4SoT6bxSGgRrjKJXJ4GDGQEgLFT92+DIaup/o+e6MV8AlTctJl2eM2PrL4Hn6YjyD /vI2PzPEDGXBUkvWu5vlPEwfPgnq+GkOz96B3Nkc8vxGMKDCOOJlnOy1DcTmVhPC1yE/ypbDsq5A2 owpRtdMD/bDDvwy1NPYEMOQCInmF9pNcrNxKmgODuTo+if43PYXpzbypOxCgUWI7QFKgyLISyw/Uq bWi0vOSnDYnVlNM2yO+/Nn5JpFaGmaiyBarDzXOqMNPfBbSAZVoQ/ZqSV9EQUcJAgVEVy6lKU6mDt hg9mQD70w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1icWa9-0001kB-BX; Wed, 04 Dec 2019 15:28:49 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BD3423006E3; Wed, 4 Dec 2019 16:27:30 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8FA1720D1A245; Wed, 4 Dec 2019 16:28:47 +0100 (CET) Date: Wed, 4 Dec 2019 16:28:47 +0100 From: Peter Zijlstra To: Fenghua Yu Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Andy Lutomirski , David Laight , Ashok Raj , Tony Luck , Ravi V Shankar , linux-kernel , x86 , richard@nod.at Subject: Re: [PATCH v2 3/4] mtd: rawnand: fsmc: Change to non-atomic bit operations Message-ID: <20191204152847.GZ2844@hirez.programming.kicks-ass.net> References: <1574710984-208305-1-git-send-email-fenghua.yu@intel.com> <1574710984-208305-4-git-send-email-fenghua.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1574710984-208305-4-git-send-email-fenghua.yu@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 25, 2019 at 11:43:03AM -0800, Fenghua Yu wrote: > No need for expensive atomic change_bit() on the local variable err_idx[]. > > Signed-off-by: Fenghua Yu > --- > drivers/mtd/nand/raw/fsmc_nand.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/mtd/nand/raw/fsmc_nand.c b/drivers/mtd/nand/raw/fsmc_nand.c > index a6964feeec77..916496d4ecf2 100644 > --- a/drivers/mtd/nand/raw/fsmc_nand.c > +++ b/drivers/mtd/nand/raw/fsmc_nand.c > @@ -809,8 +809,8 @@ static int fsmc_bch8_correct_data(struct nand_chip *chip, u8 *dat, > > i = 0; > while (num_err--) { > - change_bit(0, (unsigned long *)&err_idx[i]); > - change_bit(1, (unsigned long *)&err_idx[i]); > + __change_bit(0, (unsigned long *)&err_idx[i]); > + __change_bit(1, (unsigned long *)&err_idx[i]); > > if (err_idx[i] < chip->ecc.size * 8) { > change_bit(err_idx[i], (unsigned long *)dat); I'm thinking this all can be written like: err_idx[i] ^= 3; if (err_idx[i] < chip->ecc.size * 8) { err = err_idx[i]; dat[err >> 3] ^= BIT(err & 7); } It seems unlikely that the @dat we're correcting has concurrency issues.