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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7673FC04AB4 for ; Tue, 21 May 2019 10:01:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5424A2173E for ; Tue, 21 May 2019 10:01:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726744AbfEUKBm (ORCPT ); Tue, 21 May 2019 06:01:42 -0400 Received: from mx2.suse.de ([195.135.220.15]:57630 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726138AbfEUKBl (ORCPT ); Tue, 21 May 2019 06:01:41 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 981ADAE48; Tue, 21 May 2019 10:01:40 +0000 (UTC) Message-ID: <1558432122.12672.12.camel@suse.com> Subject: Re: [PATCH v2] usbnet: fix kernel crash after disconnect From: Oliver Neukum To: Kloetzke Jan , "davem@davemloft.net" Cc: "jan@kloetzke.net" , "linux-usb@vger.kernel.org" , "netdev@vger.kernel.org" Date: Tue, 21 May 2019 11:48:42 +0200 In-Reply-To: <1557990629.19453.7.camel@preh.de> References: <1556563688.20085.31.camel@suse.com> <20190430141440.9469-1-Jan.Kloetzke@preh.de> <20190505.004556.492323065607253635.davem@davemloft.net> <1557130666.12778.3.camel@suse.com> <1557990629.19453.7.camel@preh.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Do, 2019-05-16 at 07:10 +0000, Kloetzke Jan wrote: > Am Montag, den 06.05.2019, 10:17 +0200 schrieb Oliver Neukum: > > On So, 2019-05-05 at 00:45 -0700, David Miller wrote: > > > From: Kloetzke Jan > > > Date: Tue, 30 Apr 2019 14:15:07 +0000 > > > > > > > @@ -1431,6 +1432,11 @@ netdev_tx_t usbnet_start_xmit (struct sk_buff *skb, > > > > spin_unlock_irqrestore(&dev->txq.lock, flags); > > > > goto drop; > > > > } > > > > + if (WARN_ON(netif_queue_stopped(net))) { > > > > + usb_autopm_put_interface_async(dev->intf); > > > > + spin_unlock_irqrestore(&dev->txq.lock, flags); > > > > + goto drop; > > > > + } > > > > > > If this is known to happen and is expected, then we should not warn. > > > > > > > Hi, > > > > yes this is the point. Can ndo_start_xmit() and ndo_stop() race? > > If not, why does the patch fix the observed issue and what > > prevents the race? Something is not clear here. > > Dave, could you shed some light on Olivers question? If the race can > happen then we can stick to v1 because the WARN_ON is indeed pointless. > Otherwise it's not clear why it made the problem go away for us and v2 > may be the better option... Hi, as Dave confirmed that the race exists, could you resubmit without the WARN ? Regards Oliver