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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F67CC433F5 for ; Tue, 12 Oct 2021 07:30:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7320260C49 for ; Tue, 12 Oct 2021 07:30:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233860AbhJLHcw (ORCPT ); Tue, 12 Oct 2021 03:32:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:53360 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232500AbhJLHcv (ORCPT ); Tue, 12 Oct 2021 03:32:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 06F2E6108F; Tue, 12 Oct 2021 07:30:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1634023850; bh=TSotnDEGPeHmunn6wztD6SCujzB/ETVss5hcrTWVz+A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=X67XZbZvYrFeVockMRI704hghYMsQqKB+nzEY6V3OkxyHJntR2DUfQRq38faROf/S 5j0yD2kv9oUE3mUcRN5BLya0yBgQY3J112v9/6Mz7dPE1JTDtQtTrN9meuJtTUTWOn oOTq+71hZF2rmaoXYaN5jFoL6NPwWWMFnBFTwUDw= Date: Tue, 12 Oct 2021 09:30:47 +0200 From: Greg Kroah-Hartman To: "Linyu Yuan (QUIC)" Cc: Felipe Balbi , "linux-usb@vger.kernel.org" Subject: Re: [PATCH v5 1/3] usb: gadget: configfs: avoid list move operation of usb_function Message-ID: References: <1630976977-13938-1-git-send-email-quic_linyyuan@quicinc.com> <1630976977-13938-2-git-send-email-quic_linyyuan@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Oct 12, 2021 at 03:54:29AM +0000, Linyu Yuan (QUIC) wrote: > > From: Greg Kroah-Hartman > > Sent: Sunday, October 10, 2021 9:05 PM > > To: Linyu Yuan (QUIC) > > Cc: Felipe Balbi ; linux-usb@vger.kernel.org > > Subject: Re: [PATCH v5 1/3] usb: gadget: configfs: avoid list move operation > > of usb_function > > > > On Sat, Oct 09, 2021 at 02:26:07AM +0000, Linyu Yuan (QUIC) wrote: > > > > From: Greg Kroah-Hartman > > > > Sent: Tuesday, October 5, 2021 7:11 PM > > > > To: Linyu Yuan (QUIC) > > > > Cc: Felipe Balbi ; linux-usb@vger.kernel.org > > > > Subject: Re: [PATCH v5 1/3] usb: gadget: configfs: avoid list move > > operation > > > > of usb_function > > > > > > > > On Tue, Sep 07, 2021 at 09:09:35AM +0800, Linyu Yuan wrote: > > > > > add a new list which link all usb_function at configfs layers, > > > > > it means that after link a function a configuration, > > > > > from configfs layer, we can still found all functions, > > > > > it will allow trace all functions from configfs. > > > > > > > > I am sorry, but I do not understand this paragraph. Can you try > > > > rewording it? > > > > > > > > > > > > > > Reported-by: kernel test robot > > > > > > > > How did the kernel test robot report this? You are adding a new > > > > function here, it is not a bug you are fixing, right? > > > > > > > > > > > > > Signed-off-by: Linyu Yuan > > > > > --- > > > > > v2: fix unused cfg variable warning > > > > > v3: add struct inside configfs.c > > > > > v4: no change > > > > > v5: lost v2 fix, add it again > > > > > > > > > > drivers/usb/gadget/configfs.c | 55 ++++++++++++++++++++++++------ > > ---- > > > > --------- > > > > > 1 file changed, 31 insertions(+), 24 deletions(-) > > > > > > > > > > diff --git a/drivers/usb/gadget/configfs.c > > b/drivers/usb/gadget/configfs.c > > > > > index 477e72a..5b2e6f9 100644 > > > > > --- a/drivers/usb/gadget/configfs.c > > > > > +++ b/drivers/usb/gadget/configfs.c > > > > > @@ -58,6 +58,11 @@ static inline struct gadget_info > > > > *to_gadget_info(struct config_item *item) > > > > > return container_of(to_config_group(item), struct gadget_info, > > > > group); > > > > > } > > > > > > > > > > +struct config_usb_function { > > > > > + struct list_head list; > > > > > + struct usb_function *f; > > > > > +}; > > > > > > > > What lock protects this list? > > > > > > > > > + > > > > > struct config_usb_cfg { > > > > > struct config_group group; > > > > > struct config_group strings_group; > > > > > @@ -420,7 +425,7 @@ static int config_usb_cfg_link( > > > > > struct usb_function_instance *fi = container_of(group, > > > > > struct usb_function_instance, group); > > > > > struct usb_function_instance *a_fi; > > > > > - struct usb_function *f; > > > > > + struct config_usb_function *cf; > > > > > int ret; > > > > > > > > > > mutex_lock(&gi->lock); > > > > > @@ -438,21 +443,29 @@ static int config_usb_cfg_link( > > > > > goto out; > > > > > } > > > > > > > > > > - list_for_each_entry(f, &cfg->func_list, list) { > > > > > - if (f->fi == fi) { > > > > > + list_for_each_entry(cf, &cfg->func_list, list) { > > > > > + if (cf->f->fi == fi) { > > > > > ret = -EEXIST; > > > > > goto out; > > > > > } > > > > > } > > > > > > > > > > - f = usb_get_function(fi); > > > > > - if (IS_ERR(f)) { > > > > > - ret = PTR_ERR(f); > > > > > + cf = kzalloc(sizeof(*cf), GFP_KERNEL); > > > > > > > > Why "kzalloc" and not "kmalloc"? > > > > > > > > I don't understand why you are moving everything to a single list in the > > > > system, what is wrong with the existing per-device one? > > > Thanks Greg, > > > > > > Let me explain what I want to do in this change, > > > > > > For original code, when add a function to configuration, it will add function > > > struct usb_function { > > > ... > > > struct list_head list; [1] > > > }; > > > to following list, > > > struct config_usb_cfg { > > > ... > > > struct list_head func_list; [2] > > > }; > > > Then when bind happen, it will move [1] to following list, > > > struct usb_configuration { > > > ... > > > struct list_head functions; [3] > > > }; > > > > > > When unbind, it will move [1] back to [2]. > > > > > > We can see list [1] move between two list head, it is not easy to trace. > > > > > > And when I add trace, I only want to get trace info from structure defined > > in configfs.c, > > > > > > So I add a new list which ONLY add/remove to head [2] and it represent a > > function in configfs layer. > > > And original list [1] will ONLY add/remove to head [3]. > > > > I am sorry, but I still do not understand. These are different types of > > things that you are now putting all on the same list? > > > > What prevents your trace functions from working today with the existing > > code? What can you not get access to? > > > > All you say here is "it is not easy to trace", but that does not explain > > _what_ you are missing and why you need to change that. > > Consider the list is moving between two list heads, > if I trace each function, It may duplicate or missing some function. > This is my simple reason. How can the list move when you are tracing? I'm sorry, I do not understand. greg k-h