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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 A4202C433B4 for ; Wed, 19 May 2021 14:36:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7FC4C61363 for ; Wed, 19 May 2021 14:36:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347956AbhESOhf (ORCPT ); Wed, 19 May 2021 10:37:35 -0400 Received: from netrider.rowland.org ([192.131.102.5]:33637 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S243400AbhESOhe (ORCPT ); Wed, 19 May 2021 10:37:34 -0400 Received: (qmail 1166645 invoked by uid 1000); 19 May 2021 10:36:13 -0400 Date: Wed, 19 May 2021 10:36:13 -0400 From: Alan Stern To: dave penkler Cc: Guido Kiener , Dmitry Vyukov , syzbot , Greg Kroah-Hartman , "lee.jones@linaro.org" , USB list , "bp@alien8.de" , "dwmw@amazon.co.uk" , "hpa@zytor.com" , "linux-kernel@vger.kernel.org" , "luto@kernel.org" , "mingo@redhat.com" , "syzkaller-bugs@googlegroups.com" , "tglx@linutronix.de" , "x86@kernel.org" Subject: Re: Re: Re: Re: Re: [syzbot] INFO: rcu detected stall in tx Message-ID: <20210519143613.GA1165692@rowland.harvard.edu> References: <6cffd7eebba54ed8acd043d51d212ec1@rohde-schwarz.com> <20210508142947.GB810516@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 19, 2021 at 10:48:29AM +0200, dave penkler wrote: > On Sat, 8 May 2021 at 16:29, Alan Stern wrote: > > > > On Sat, May 08, 2021 at 10:14:41AM +0200, dave penkler wrote: > > > When the host driver detects a protocol error while processing an URB > > > it completes the URB with EPROTO status and marks the endpoint as > > > halted. > > > > Not true. It does not mark the endpoint as halted, not unless it > > receives a STALL handshake from the device. A STALL is not a protocol > > error. > > > > > When the class driver resubmits the URB and the if the host driver > > > finds the endpoint still marked as halted it should return EPIPE > > > status on the resubmitted URB > > > > Irrelevant. > Not at all. The point is that when an application is talking to an > instrument over the usbtmc driver, the underlying host controller and > its driver will detect and silence a babbling endpoint. No, they won't. That is, they will detect a babble error and return an error status, but they won't silence the endpoint. What makes you think they will? > Hence no EPROTO loop will ensue in this case and therefore no changes > are needed in usbtmc. Since this conclusion relies on the incorrect assumption above, it also is incorrect. Alan Stern