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=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT 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 F25EEC04EB9 for ; Wed, 17 Oct 2018 03:50:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD8DE214C4 for ; Wed, 17 Oct 2018 03:50:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD8DE214C4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codemonkey.org.uk 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 S1727461AbeJQLoR (ORCPT ); Wed, 17 Oct 2018 07:44:17 -0400 Received: from scorn.kernelslacker.org ([45.56.101.199]:41390 "EHLO scorn.kernelslacker.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727162AbeJQLoQ (ORCPT ); Wed, 17 Oct 2018 07:44:16 -0400 Received: from [2601:196:4600:5b90:ae9e:17ff:feb7:72ca] (helo=wopr.kernelslacker.org) by scorn.kernelslacker.org with esmtp (Exim 4.89) (envelope-from ) id 1gCcr0-000756-OV; Tue, 16 Oct 2018 23:50:38 -0400 Received: by wopr.kernelslacker.org (Postfix, from userid 1026) id 9DFCD56010A; Tue, 16 Oct 2018 23:50:38 -0400 (EDT) Date: Tue, 16 Oct 2018 23:50:38 -0400 From: Dave Jones To: Cong Wang , Meelis Roos , LKML , Linux Kernel Network Developers Subject: Re: netconsole warning in 4.19.0-rc7 Message-ID: <20181017035038.czaqown24rnjn2pw@codemonkey.org.uk> Mail-Followup-To: Dave Jones , Cong Wang , Meelis Roos , LKML , Linux Kernel Network Developers References: <20181017034047.nrhstc3b4wzevnri@codemonkey.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181017034047.nrhstc3b4wzevnri@codemonkey.org.uk> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 16, 2018 at 11:40:47PM -0400, Dave Jones wrote: > > This is exactly what I mentioned in my review here: > > https://marc.info/?l=linux-netdev&m=153816136624679&w=2 > > > > "But irq is disabled here, so not sure if rcu_read_lock_bh() > > could cause trouble... " > > Not sure why this didn't show up for me when I was developing that > patch, but I can now reproduce this. The patch below fixes it for > me, but I'm not sure if there are still any side-effects. > There's also a missed unlock in the error path. I took another look at that error path. Turns out this is all we need I think.. diff --git a/net/core/netpoll.c b/net/core/netpoll.c index de1d1ba92f2d..f9322d5db899 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -318,6 +318,7 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb, npinfo = rcu_dereference_bh(np->dev->npinfo); if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) { dev_kfree_skb_irq(skb); + rcu_read_unlock_bh(); return; }