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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35A1DCCA48C for ; Tue, 26 Jul 2022 06:47:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237946AbiGZGrc (ORCPT ); Tue, 26 Jul 2022 02:47:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59310 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232263AbiGZGr3 (ORCPT ); Tue, 26 Jul 2022 02:47:29 -0400 Received: from ZXSHCAS1.zhaoxin.com (ZXSHCAS1.zhaoxin.com [210.0.225.54]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D909A1EAFE; Mon, 25 Jul 2022 23:47:26 -0700 (PDT) Received: from zxbjmbx1.zhaoxin.com (10.29.252.163) by ZXSHCAS1.zhaoxin.com (10.28.252.161) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.27; Tue, 26 Jul 2022 14:47:00 +0800 Received: from [10.29.8.21] (10.29.8.21) by zxbjmbx1.zhaoxin.com (10.29.252.163) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.27; Tue, 26 Jul 2022 14:46:59 +0800 Message-ID: <3f2c941b-94cd-8357-13de-8656486e8cbd@zhaoxin.com> Date: Tue, 26 Jul 2022 14:46:57 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v2] USB: HCD: Fix URB giveback issue in tasklet function Content-Language: en-US To: Alan Stern CC: , , , , , , , , , , References: <20220725065251.832087-1-WeitaoWang-oc@zhaoxin.com> From: "WeitaoWang-oc@zhaoxin.com" In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.29.8.21] X-ClientProxiedBy: ZXSHCAS1.zhaoxin.com (10.28.252.161) To zxbjmbx1.zhaoxin.com (10.29.252.163) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/7/25 21:58, Alan Stern wrote: > On Mon, Jul 25, 2022 at 02:52:51PM +0800, Weitao Wang wrote: > > This is basically okay. Just a couple of small comments... > >> Usb core introduce the mechanism of giveback of URB in tasklet context to >> reduce hardware interrupt handling time. On some test situation(such as >> FIO with 4KB block size), when tasklet callback function called to >> giveback URB, interrupt handler add URB node to the bh->head list also. >> If check bh->head list again after finish all URB giveback of local_list, >> then it may introduce a "dynamic balance" between giveback URB and add URB >> to bh->head list. This tasklet callback function may not exit for a long >> time, which will cause other tasklet function calls to be delayed. Some >> real-time applications(such as KB and Mouse) will see noticeable lag. >> >> Fix this issue by taking new URBs giveback in next tasklet function call. >> Add a member high_prio for structure giveback_urb_bh and replace the local >> high_prio_bh variable with this structure member in usb_hcd_giveback_urb. > > The patch description should do more than say what the new code _is_ -- > we can see that easily enough by reading the patch. The description > should explain _why_ the code was changed. > Okay, I will improve this patch description. >> - /* check if there are new URBs to giveback */ >> + /* giveback new URBs next time to prevent this function from >> + * not exiting for a long time. >> + */ > > Minor stylistic issue: The currently accepted format for multi-line > comments is like this: > This notes will be improved in next patch version also. Thanks for your suggestion. weitao > /* > * Blah blah blah > * Blah blah blah > */ > > Alan Stern > .