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[23.128.96.18]) by mx.google.com with ESMTP id b31si7585794edf.440.2021.05.08.01.19.47; Sat, 08 May 2021 01:20:11 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@mg.codeaurora.org header.s=smtp header.b=BA1xC97K; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230089AbhEHIQ4 (ORCPT + 99 others); Sat, 8 May 2021 04:16:56 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:56187 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229797AbhEHIQz (ORCPT ); Sat, 8 May 2021 04:16:55 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1620461753; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=0KPm7oGzmL0q2aWv65LlrmKsUkDV5qha/CX/tq0j1zM=; b=BA1xC97KHfkE4b8gMiiv8LcsxN99MDlXhIHusYxz5KxB918RU5J+Q7EEiamLIzJqN6K7W8+N uE0Xp4aDP4bvtFrsR3EC/DuffwMLc2nKSoyj+/7D3JP5ebak299WbxksXU153KzFeg55PqZd 46L6BqOsHUXRvSqUVIv17GfDJ0E= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n01.prod.us-east-1.postgun.com with SMTP id 609648b987ce1fbb563eaca5 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Sat, 08 May 2021 08:15:53 GMT Sender: wcheng=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 6FEC7C43145; Sat, 8 May 2021 08:15:52 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-caf-mail-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=ALL_TRUSTED,BAYES_00, NICE_REPLY_A,SPF_FAIL autolearn=no autolearn_force=no version=3.4.0 Received: from [10.110.52.184] (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 D568CC4338A; Sat, 8 May 2021 08:15:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org D568CC4338A 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] usb: dwc3: gadget: Replace list_for_each_entry_safe() if using giveback To: Peter Chen Cc: balbi@kernel.org, gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, jackp@codeaurora.org References: <1620412923-11990-1-git-send-email-wcheng@codeaurora.org> <20210508034551.GA2728@nchen> From: Wesley Cheng Message-ID: Date: Sat, 8 May 2021 01:15:49 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210508034551.GA2728@nchen> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/7/2021 8:45 PM, Peter Chen wrote: > On 21-05-07 11:42:03, Wesley Cheng wrote: >> 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, Hi Peter, Thanks for the review. > > I see dwc3_gadget_del_and_unmap_request remove the list, the lock is > still held there. Am I something wrong? > The scenario the issue happens in is say the follow thread is running the sequence below: Thread#1: __dwc3_gadget_ep_set_halt() - CLEAR HALT -> dwc3_gadget_ep_cleanup_cancelled_requests() ->list_for_each_entry_safe() ->dwc3_gadget_giveback() ->dwc3_gadget_del_and_unmap_request()-n deleted cancelled_list ->spin_unlock 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 So now, if thread#1 takes the DWC3 lock again, it will continue to item n+1, which was already removed by thread#2, leading to a double list removal. We saw this issue on our platform after enabling list debug. Thanks Wesley Cheng > Peter > >> 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. >> >> Fixes: d4f1afe5e896 ("usb: dwc3: gadget: move requests to cancelled_list") >> Signed-off-by: Wesley Cheng >> --- >> 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); >> dwc3_gadget_ep_skip_trbs(dep, req); >> switch (req->status) { >> case DWC3_REQUEST_STATUS_DISCONNECTED: >> @@ -2935,11 +2935,11 @@ static void dwc3_gadget_ep_cleanup_completed_requests(struct dwc3_ep *dep, >> const struct dwc3_event_depevt *event, int status) >> { >> struct dwc3_request *req; >> - struct dwc3_request *tmp; >> >> - list_for_each_entry_safe(req, tmp, &dep->started_list, list) { >> + while (!list_empty(&dep->started_list)) { >> int ret; >> >> + req = next_request(&dep->started_list); >> ret = dwc3_gadget_ep_cleanup_completed_request(dep, event, >> req, status); >> if (ret) >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, >> a Linux Foundation Collaborative Project >> > -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project