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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 3B326C4321E for ; Mon, 10 Sep 2018 11:27:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E5E4D2087E for ; Mon, 10 Sep 2018 11:27:15 +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="eQPVGZae" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E5E4D2087E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728407AbeIJQUt (ORCPT ); Mon, 10 Sep 2018 12:20:49 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:54710 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727411AbeIJQUt (ORCPT ); Mon, 10 Sep 2018 12:20:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=Mk1HL1H+7x4g6lTZivnPI31Ajh6Emm2JYk8arraEwyM=; b=eQPVGZaeEGlAmOaRLd/AKMpCd QyvSCBbT4ZImvu3chBRwmKTq3TgmLCaedNGsnlrPeTQxTjeofRMFHGccB5k/yPTnIcuOsYIOsdmmu aHRO1D2zTW5xdVwXnvX4jRW+KEmuWuTFCKVSeZ4363u4ubKaLRxVoN8njUCjDQWAiPkYHEk3oCTqw eQhA+hgcg51/8Hgv0pJOO+2Ek++B+KdeePWTCxiU2+5FG6VIxgB4lqcpRaY3xLOqPGq2dVB8qJ021 CYmSqPQBOrT9FEo79SbxEWguGuuVOjG5e4LCimUN0bmeRh3OdkKJhVelIPbtMOa1UT3UNqarOWKgu H/l2LPEng==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fzKLV-00079C-Gz; Mon, 10 Sep 2018 11:27:09 +0000 Date: Mon, 10 Sep 2018 04:27:09 -0700 From: Christoph Hellwig To: Atish Patra Cc: palmer@sifive.com, linux-riscv@lists.infradead.org, hch@infradead.org, anup@brainfault.org, mark.rutland@arm.com, Damien.LeMoal@wdc.com, jason@lakedaemon.net, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, gregkh@linuxfoundation.org, dmitriy@oss-tech.org, linux-kernel@vger.kernel.org, jeremy.linton@arm.com, catalin.marinas@arm.com, tglx@linutronix.de Subject: Re: [PATCH v3 09/12] RISC-V: User WRITE_ONCE instead of direct access Message-ID: <20180910112709.GH12979@infradead.org> References: <1536221135-182613-1-git-send-email-atish.patra@wdc.com> <1536221135-182613-10-git-send-email-atish.patra@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1536221135-182613-10-git-send-email-atish.patra@wdc.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 06, 2018 at 01:05:32AM -0700, Atish Patra wrote: > The secondary harts spin on couple of per cpu variables until both of > these are non-zero so it's not necessary to have any ordering here. > However, WRITE_ONCE should be used to avoid tearing. We normally pair WRITE_ONCE with READ_ONCE. But it seems like the reader side is in assembly code, so this should be ok: Reviewed-by: Christoph Hellwig