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=-15.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 BCB2DC48BCF for ; Wed, 9 Jun 2021 20:57:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 972F8613EE for ; Wed, 9 Jun 2021 20:57:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229771AbhFIU7q (ORCPT ); Wed, 9 Jun 2021 16:59:46 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:47095 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229578AbhFIU7p (ORCPT ); Wed, 9 Jun 2021 16:59:45 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1623272270; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: References: Cc: To: From: Subject: Sender; bh=nzlPsbiXe8YZGFdkYnkK+8MI+UNQoJBQtFJDPoUTWE8=; b=pDL1ow8ZPwGOoDBLO9M9hKCjBYPS1PDWIBKhIWx73QEscNpQBNstGzLm/+L+J3wK/gJxmA13 DytsS3Y99H2zt7obkZCQlM28eC+7BYKIcAj37wRQCJTe1pbCoRM1NpTyb5w1oPAoaQnld4ng qdK3WW74lsh4EVvDJORukyQdj7w= X-Mailgun-Sending-Ip: 69.72.43.7 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-n06.prod.us-east-1.postgun.com with SMTP id 60c12b3df726fa4188d0e0e8 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Wed, 09 Jun 2021 20:57:33 GMT Sender: wcheng=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id DACDFC4338A; Wed, 9 Jun 2021 20:57:32 +0000 (UTC) Received: from [10.110.62.3] (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 CEDCBC433D3; Wed, 9 Jun 2021 20:57:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org CEDCBC433D3 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: Replace list_for_each_entry_safe() if using giveback From: Wesley Cheng To: Felipe Balbi , gregkh@linuxfoundation.org, peter.chen@kernel.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, jackp@codeaurora.org References: <1620716636-12422-1-git-send-email-wcheng@codeaurora.org> <87tun9g01v.fsf@kernel.org> <2675db9e-0cab-06b5-2986-0b4456a1f040@codeaurora.org> Message-ID: <5156238d-c1d8-a0d3-47af-8b52467fd071@codeaurora.org> Date: Wed, 9 Jun 2021 13:57:30 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <2675db9e-0cab-06b5-2986-0b4456a1f040@codeaurora.org> 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 Hi Felipe, On 5/19/2021 1:52 AM, Wesley Cheng wrote: > > > On 5/11/2021 1:13 AM, Felipe Balbi wrote: >> >> Hi, >> >> Wesley Cheng writes: >>> The list_for_each_entry_safe() macro saves the current item (n) and >>> the item after (n+1), so that n can be safely removed without >>> corrupting the list. However, when traversing the list and removing >>> items using gadget giveback, the DWC3 lock is briefly released, >>> allowing other routines to execute. There is a situation where, while >>> items are being removed from the cancelled_list using >>> dwc3_gadget_ep_cleanup_cancelled_requests(), the pullup disable >>> routine is running in parallel (due to UDC unbind). As the cleanup >>> routine removes n, and the pullup disable removes n+1, once the >>> cleanup retakes the DWC3 lock, it references a request who was already >>> removed/handled. With list debug enabled, this leads to a panic. >>> Ensure all instances of the macro are replaced where gadget giveback >>> is used. >>> >>> Example call stack: >>> >>> Thread#1: >>> __dwc3_gadget_ep_set_halt() - CLEAR HALT >>> -> dwc3_gadget_ep_cleanup_cancelled_requests() >>> ->list_for_each_entry_safe() >>> ->dwc3_gadget_giveback(n) >>> ->dwc3_gadget_del_and_unmap_request()- n deleted[cancelled_list] >>> ->spin_unlock >>> ->Thread#2 executes >>> ... >>> ->dwc3_gadget_giveback(n+1) >>> ->Already removed! >>> >>> Thread#2: >>> dwc3_gadget_pullup() >>> ->waiting for dwc3 spin_lock >>> ... >>> ->Thread#1 released lock >>> ->dwc3_stop_active_transfers() >>> ->dwc3_remove_requests() >>> ->fetches n+1 item from cancelled_list (n removed by Thread#1) >>> ->dwc3_gadget_giveback() >>> ->dwc3_gadget_del_and_unmap_request()- n+1 deleted[cancelled_list] >>> ->spin_unlock >>> >>> Fixes: d4f1afe5e896 ("usb: dwc3: gadget: move requests to cancelled_list") >>> Signed-off-by: Wesley Cheng >>> Reviewed-by: Peter Chen >>> --- >>> Changes in v2: >>> - Updated commit message with context call stack of an example scenario >>> seen on device. >>> >>> drivers/usb/dwc3/gadget.c | 8 ++++---- >>> 1 file changed, 4 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c >>> index dd80e5c..efa939b 100644 >>> --- a/drivers/usb/dwc3/gadget.c >>> +++ b/drivers/usb/dwc3/gadget.c >>> @@ -1737,10 +1737,10 @@ static void dwc3_gadget_ep_skip_trbs(struct dwc3_ep *dep, struct dwc3_request *r >>> static void dwc3_gadget_ep_cleanup_cancelled_requests(struct dwc3_ep *dep) >>> { >>> struct dwc3_request *req; >>> - struct dwc3_request *tmp; >>> struct dwc3 *dwc = dep->dwc; >>> >>> - list_for_each_entry_safe(req, tmp, &dep->cancelled_list, list) { >>> + while (!list_empty(&dep->cancelled_list)) { >>> + req = next_request(&dep->cancelled_list); >> >> couldn't this be solved list_replace_init() instead? Then we can keep >> using the regular list_for_each_entry_safe() which has an added semantic >> meaning due to its name. >> > > Hi Felipe, > > Sorry for the late response. So I tried with a list_replace_init() to > within the list_for_each_entry_safe() loop to update tmp w/ the > cancelled_list list head, but the issue was still observed. This is > because we can't replace the reference the loop already has stored in > tmp, which is simply updated as the current item on the next iteration. > > I believe this is what you were trying to achieve? > Was wondering if you had any further inputs on this change? As mentioned, I tried a few things with list_replace_init(), which did not work. Thanks Wesley Cheng -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project