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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no 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 E484CC7618F for ; Thu, 18 Jul 2019 23:30:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C229220873 for ; Thu, 18 Jul 2019 23:30:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726135AbfGRXao (ORCPT ); Thu, 18 Jul 2019 19:30:44 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:57178 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbfGRXan (ORCPT ); Thu, 18 Jul 2019 19:30:43 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 353511528C8BD; Thu, 18 Jul 2019 16:30:43 -0700 (PDT) Date: Thu, 18 Jul 2019 16:30:42 -0700 (PDT) Message-Id: <20190718.163042.844837284595324517.davem@davemloft.net> To: brking@linux.vnet.ibm.com Cc: GR-everest-linux-l2@marvell.com, skalluru@marvell.com, aelior@marvell.com, netdev@vger.kernel.org Subject: Re: [PATCH] bnx2x: Prevent load reordering in tx completion processing From: David Miller In-Reply-To: <1563226910-21660-1-git-send-email-brking@linux.vnet.ibm.com> References: <1563226910-21660-1-git-send-email-brking@linux.vnet.ibm.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Thu, 18 Jul 2019 16:30:43 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Brian King Date: Mon, 15 Jul 2019 16:41:50 -0500 > This patch fixes an issue seen on Power systems with bnx2x which results > in the skb is NULL WARN_ON in bnx2x_free_tx_pkt firing due to the skb > pointer getting loaded in bnx2x_free_tx_pkt prior to the hw_cons > load in bnx2x_tx_int. Adding a read memory barrier resolves the issue. > > Signed-off-by: Brian King I agree with Brian's explanation of how the reordering can happen, and why the crash doesn't show up in the prefetch() call. I'll give the Marvell folks one more day to give a proper ACK. Thanks.