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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 0372EC47084 for ; Mon, 24 May 2021 15:23:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DDD996140E for ; Mon, 24 May 2021 15:23:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234333AbhEXPZZ (ORCPT ); Mon, 24 May 2021 11:25:25 -0400 Received: from mga01.intel.com ([192.55.52.88]:42144 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234710AbhEXPTI (ORCPT ); Mon, 24 May 2021 11:19:08 -0400 IronPort-SDR: SYBoUnnQm2q+7th+Jj9bTIcIhW7dxRiCxVlJsl2RGU+8waxuAzElwoXdB5Xy7soCul7H5zSSqE 7mdL6OMSX3WQ== X-IronPort-AV: E=McAfee;i="6200,9189,9993"; a="223112149" X-IronPort-AV: E=Sophos;i="5.82,325,1613462400"; d="scan'208";a="223112149" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 May 2021 08:16:55 -0700 IronPort-SDR: VIVaZbCdfDH8Lc9UdKdvRNZQD1T/NVbzspLek31O8Ej5w/Zilu7NhU64PtAcFK/DTIQW48mG2n FPw5sL+mAqYQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,325,1613462400"; d="scan'208";a="442079811" Received: from mattu-haswell.fi.intel.com (HELO [10.237.72.170]) ([10.237.72.170]) by orsmga008.jf.intel.com with ESMTP; 24 May 2021 08:16:50 -0700 Subject: Re: [syzbot] INFO: rcu detected stall in tx To: Thinh Nguyen , Alan Stern , Mathias Nyman Cc: Guido Kiener , dave penkler , 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" References: <20210519173545.GA1173157@rowland.harvard.edu> <12088413-2f7d-a1e5-5e8a-25876d85d18a@synopsys.com> <20210520020117.GA1186755@rowland.harvard.edu> <74b2133b-2f77-c86f-4c8b-1189332617d3@synopsys.com> From: Mathias Nyman Autocrypt: addr=mathias.nyman@linux.intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <74b2133b-2f77-c86f-4c8b-1189332617d3@synopsys.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20.5.2021 23.30, Thinh Nguyen wrote: > +Mathias > ... > Hm... looks like we have a couple of issues in the uas storage class > driver and the xhci driver. > > We may need to fix that in the uas storage driver because it doesn't > seem to handle it. (check uas_data_cmplt() in uas.c). > > As for the xhci driver, there maybe a case where the stream URB never > gets to complete because the transaction err_count is not properly > updated. The err_count for transaction error is stored in ep_ring, but > the xhci driver may not be able to lookup the correct ep_ring based on > TRB address for streams. There are cases for streams where the event > TRBs have their TRB pointer field cleared to '0' (xhci spec section > 4.12.2). If the xhci driver doesn't see ep_ring for transaction error, > it automatically does a soft-retry. This is seen from one of our > testings that the driver was repeatedly doing soft-retry until the class > driver timed out. > > Hi Mathias, maybe you have some comment on this? Thanks. This is true, if TRB pointer is 0 then there is no retry limit for soft retry. We should add one and prevent a loop. after e few soft resets we can end with a hard reset to clear the host side endpoint halt. We don't know the URB that was being tansferred during the error, and can't give it back with a proper error code. In that sense we still end up waiting for a timeout and someone to cancel the urb. -Mathias