From patchwork Sat Feb 6 10:49:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?b?SsO8cmdlbiBHcm/Dnw==?= X-Patchwork-Id: 12072087 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=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 B54FCC4332D for ; Sat, 6 Feb 2021 10:50:14 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 785BE64E40 for ; Sat, 6 Feb 2021 10:50:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 785BE64E40 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.82126.151834 (Exim 4.92) (envelope-from ) id 1l8LAD-0006BJ-UE; Sat, 06 Feb 2021 10:50:05 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 82126.151834; Sat, 06 Feb 2021 10:50:05 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l8LAD-0006Al-JZ; Sat, 06 Feb 2021 10:50:05 +0000 Received: by outflank-mailman (input) for mailman id 82126; Sat, 06 Feb 2021 10:50:03 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l8LAB-0005VY-Ir for xen-devel@lists.xenproject.org; Sat, 06 Feb 2021 10:50:03 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 1794a89d-3d36-4a2e-a112-1c1b7b15abf5; Sat, 06 Feb 2021 10:49:49 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 14272AEC4; Sat, 6 Feb 2021 10:49:48 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 1794a89d-3d36-4a2e-a112-1c1b7b15abf5 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1612608588; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+KP59jAs7saISZqMq/sKJ7ioUVrcML6xC9JkBIsqGnM=; b=TsFTkQEp8+BbnvC9FjNahPV9/OMDu5YaNXS+RFx2/56hsUmQ/m0XUeQohZt+9dc2pfi1Mn ZU+VYw6cMqbxpx1pFdD2FvUGZB/ZCLAbWKkk91aj4rxBdlcpSAkz8uFWYX1MaivEDbUOI9 oCisMByJFL/PfB9JBHXl3fq+xzZFIRs= From: Juergen Gross To: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: Juergen Gross , Boris Ostrovsky , Stefano Stabellini Subject: [PATCH 7/7] xen/evtchn: read producer index only once Date: Sat, 6 Feb 2021 11:49:32 +0100 Message-Id: <20210206104932.29064-8-jgross@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210206104932.29064-1-jgross@suse.com> References: <20210206104932.29064-1-jgross@suse.com> MIME-Version: 1.0 In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off-by: Juergen Gross --- drivers/xen/evtchn.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c index 421382c73d88..f6b199b597bf 100644 --- a/drivers/xen/evtchn.c +++ b/drivers/xen/evtchn.c @@ -211,7 +211,7 @@ static ssize_t evtchn_read(struct file *file, char __user *buf, goto unlock_out; c = u->ring_cons; - p = u->ring_prod; + p = READ_ONCE(u->ring_prod); if (c != p) break;