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,DKIM_SIGNED, DKIM_VALID,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 0E749C433ED for ; Tue, 4 May 2021 08:25:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9CA16023C for ; Tue, 4 May 2021 08:25:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230015AbhEDIZ4 (ORCPT ); Tue, 4 May 2021 04:25:56 -0400 Received: from so254-9.mailgun.net ([198.61.254.9]:15950 "EHLO so254-9.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229831AbhEDIZz (ORCPT ); Tue, 4 May 2021 04:25:55 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1620116700; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=hGiADiVYbn1GAyE0o74yZslVUqdaLzGRe9aZ/mqTyvQ=; b=p91UX2+nQV+j4UkMzIPHhjc0FilieQbPURDMhkD/p6DpDbfNbpIBnGCmQ3JNLPulG7Q1748L ZDIvXF5Caq4p7ijjIS1rEn1u8sOd/Vb/sCORGQzJ5kBl3YucHAiXR9Li7wWt493zHSunYgfe mRNs03nMJhuTporwOC+pc4BR/uw= X-Mailgun-Sending-Ip: 198.61.254.9 X-Mailgun-Sid: WyIxZTE2YSIsICJsaW51eC11c2JAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n02.prod.us-east-1.postgun.com with SMTP id 609104cd8166b7eff79b17df (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 04 May 2021 08:24:45 GMT Sender: wcheng=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id C0DF3C4323A; Tue, 4 May 2021 08:24:44 +0000 (UTC) Received: from [10.110.61.52] (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: wcheng) by smtp.codeaurora.org (Postfix) with ESMTPSA id 2F360C433D3; Tue, 4 May 2021 08:24:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 2F360C433D3 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=wcheng@codeaurora.org Subject: Re: [PATCH v2] usb: dwc3: gadget: Avoid canceling current request for queuing error To: Thinh Nguyen , "balbi@kernel.org" , "gregkh@linuxfoundation.org" Cc: "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "jackp@codeaurora.org" References: <1620091264-418-1-git-send-email-wcheng@codeaurora.org> <5b46e4a1-93ef-2d17-048b-5b4ceba358ae@synopsys.com> <513e6c16-9586-c78e-881b-08e0a73c50a8@codeaurora.org> <7ef627cf-3f8f-8a52-52c4-ac67ab48b87d@codeaurora.org> <5c06dc0a-4274-b6f0-3844-bd8afa1a59f9@synopsys.com> From: Wesley Cheng Message-ID: Date: Tue, 4 May 2021 01:24:42 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <5c06dc0a-4274-b6f0-3844-bd8afa1a59f9@synopsys.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 5/3/2021 10:22 PM, Thinh Nguyen wrote: > Wesley Cheng wrote: >> >> >> On 5/3/2021 8:12 PM, Thinh Nguyen wrote: >>> Hi Wesley, >>> >>> Wesley Cheng wrote: >>>> >>>> >>>> On 5/3/2021 7:20 PM, Thinh Nguyen wrote: >>>>> Hi, >>>>> >>>>> Wesley Cheng wrote: >>>>>> If an error is received when issuing a start or update transfer >>>>>> command, the error handler will stop all active requests (including >>>>>> the current USB request), and call dwc3_gadget_giveback() to notify >>>>>> function drivers of the requests which have been stopped. Avoid >>>>>> having to cancel the current request which is trying to be queued, as >>>>>> the function driver will handle the EP queue error accordingly. >>>>>> Simply unmap the request as it was done before, and allow previously >>>>>> started transfers to be cleaned up. >>>>>> >>>> >>>> Hi Thinh, >>>> >>>>> >>>>> It looks like you're still letting dwc3 stopping and cancelling all the >>>>> active requests instead letting the function driver doing the dequeue. >>>>> >>>> >>>> Yeah, main issue isn't due to the function driver doing dequeue, but >>>> having cleanup (ie USB request free) if there is an error during >>>> usb_ep_queue(). >>>> >>>> The function driver in question at the moment is the f_fs driver in AIO >>>> mode. When async IO is enabled in the FFS driver, every time it queues >>>> a packet, it will allocate a io_data struct beforehand. If the >>>> usb_ep_queue() fails it will free this io_data memory. Problem is that, >>>> since the DWC3 gadget calls the completion with -ECONNRESET, the FFS >>>> driver will also schedule a work item (within io_data struct) to handle >>>> the completion. So you end up with a flow like below >>>> >>>> allocate io_data (ffs) >>>> --> usb_ep_queue() >>>> --> __dwc3_gadget_kick_transfer() >>>> --> dwc3_send_gadget_ep_cmd(EINVAL) >>>> --> dwc3_gadget_ep_cleanup_cancelled_requests() >>>> --> dwc3_gadget_giveback(ECONNRESET) >>>> ffs completion callback >>>> queue work item within io_data >>>> --> usb_ep_queue returns EINVAL >>>> ffs frees io_data >>>> ... >>>> >>>> work scheduled >>>> --> NULL pointer/memory fault as io_data is freed >> >> Hi Thinh, >> >>> >>> sounds like a race issue. >>> >> >> It'll always happen if usb_ep_queue() fails with an error. Sorry for not >> clarifying, but the "..." represents executing in a different context >> :). Anything above the "..." is in the same context. >>>> >>>>> BTW, what kinds of command and error do you see in your setup and for >>>>> what type endpoint? I'm thinking of letting the function driver to >>>>> dequeue the requests instead of letting dwc3 automatically >>>>> ending/cancelling the queued requests. However, it's a bit tricky to do >>>>> that if the error is -ETIMEDOUT since we're not sure if the controller >>>>> had already cached the TRBs. >>>>> >>>> >>>> Happens on bulk EPs so far, but I think it wouldn't matter as long as >>>> its over the FFS interface. (and using async IO transfers) >>> >>> Do you know which command and error code? It's strange if >>> UPDATE_TRANSFER command failed. >>> >> >> Sorry for missing that part of the question. It is a no xfer resource >> error on a start transfer command. So far this happens on low system >> memory test cases, so there may be some sequences that were missed, >> which led to this particular command error. >> >> Thanks >> Wesley Cheng Hi Thinh, > > No xfer resource usually means that the driver attempted to send > START_TRANSFER without waiting for END_TRANSFER command to complete. > This may be a dwc3 driver issue. Did you check this? > > Thanks, > Thinh > > Yes, we know the reason why this happens, and its due to one of the downstream changes we had that led to the scenario above. Although, that has been fixed, I still believe the error path is a potential scenario we'd still want to address. I think the returning success always on dwc3_gadget_ep_queue(), and allowing the error in the completion handler/giveback at the function driver level to do the cleanup is a feasible solution. Doesn't change the flow of the DWC3 gadget, and so far all function drivers we've used handle this in the correct manner. Thanks Wesley Cheng >> >>>> >>>>> This seems to add more complexity and I don't have a good solution to >>>>> it. Since you're already cancelling all the active request anyway, what >>>>> do you think of always letting dwc3_gadget_ep_queue() to go through with >>>>> success, but report failure through request completion? >>>>> >>>> >>>> We do have something similar as well downstream (returning success >>>> always on dwc3_gadget_ep_queue()) and its been working for us also. >>>> Problem is we don't test the ISOC path much, so this is the only type of >>>> EP that might come into question... >>>> >>> >>> It should be similiar with isoc. I can't think of a potential issue yet. >>> >>>> Coming up with a way to address the concerns you brought up was a bit >>>> difficult as there were scenarios we needed to consider. next_request() >>>> doesn't always have to be the request being queued (even if ep queue >>>> triggered it). There was no easy way to determine if kick transfer was >>>> due to ep queue, but even if there was, we'd need to remember the >>>> previous point as well. >>>> >>> >>> Yeah, there are a few pitfalls. I don't have a good solution to it if we >>> want to return failure immediately and let the function driver handle >>> the dequeue (if it wants to). >>> >>> Thanks, >>> Thinh >>> >> > -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project