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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 7431DC433DF for ; Fri, 31 Jul 2020 11:55:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B26122BF3 for ; Fri, 31 Jul 2020 11:55:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596196551; bh=OkDkFKOa3+CujNapZuZR6KkJKd9OiUv4PIltSXghvzQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=QYoDgn5ydPWCwLptzVEIIG6eDrsTKGvnVmLp0zYv9NyMs31hGZKPHV6IPGgrNptSW 9b8bYBk5Ck73Ket1PBtxES0hGD4cXpQFMHsrg4UML1O1hyon5D9EMHu8Vc7TRAGyrs ytTgF0w0MBJIsz3zZnc6gfbPczltCKVZQ1UzKjbI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732689AbgGaLzu (ORCPT ); Fri, 31 Jul 2020 07:55:50 -0400 Received: from mail.kernel.org ([198.145.29.99]:51602 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732512AbgGaLzu (ORCPT ); Fri, 31 Jul 2020 07:55:50 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3285B2245C; Fri, 31 Jul 2020 11:55:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1596196549; bh=OkDkFKOa3+CujNapZuZR6KkJKd9OiUv4PIltSXghvzQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UWXcZOePOFOkogBuP97IQ8SxyjYp41AulIh+Wi5w/X/vxQk62pe/+3iDkn9Wd+WAf Z/yWfe3Q2WK71rh38MWgwpubdDaPzB+2I613A/jjFDj/KPdZkQTaqqf7JDLLuVYCm6 veJql/h5Yp1P1DI9ecnOLh3xQb4xzwnbTuwEHGH4= Date: Fri, 31 Jul 2020 13:55:36 +0200 From: Greg Kroah-Hartman To: Peter Chen Cc: balbi@kernel.org, linux-usb@vger.kernel.org, linux-imx@nxp.com, Alan Stern Subject: Re: [PATCH 1/1] usb: gadget: core: wait gadget device .release finishing at usb_del_gadget_udc Message-ID: <20200731115536.GB1648202@kroah.com> References: <20200731095935.23034-1-peter.chen@nxp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200731095935.23034-1-peter.chen@nxp.com> Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Fri, Jul 31, 2020 at 05:59:35PM +0800, Peter Chen wrote: > Per discussion[1], to avoid UDC driver possible freeing gadget device > memory before device core finishes using it, we add wait-complete > mechanism at usb_del_gadget_udc and gadget device .release callback. > After that, usb_del_gadget_udc will not return back until device > core finishes using gadget device. Ick, no, that's a sure way for a deadlock to happen. Why does the gadget core care about this at all? It shouldn't. > > For UDC drivers who have own .release callback, it needs to call > complete(&gadget->done) by themselves, if not, the UDC core will > handle it by default .release callback usb_gadget_release. > > [1] https://www.spinics.net/lists/linux-usb/msg198790.html > > Cc: Greg Kroah-Hartman > Cc: Alan Stern > Suggested-by: Alan Stern > Signed-off-by: Peter Chen > --- > If this RFC patch is ok, I will create the formal patches which will change > UDC drivers who have their own .release function. > > drivers/usb/gadget/udc/core.c | 14 +++++++++++--- > include/linux/usb/gadget.h | 2 ++ > 2 files changed, 13 insertions(+), 3 deletions(-) > > diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c > index ee226ad802a4..ed141e1a0dcf 100644 > --- a/drivers/usb/gadget/udc/core.c > +++ b/drivers/usb/gadget/udc/core.c > @@ -1138,9 +1138,15 @@ static void usb_udc_release(struct device *dev) > > static const struct attribute_group *usb_udc_attr_groups[]; > > -static void usb_udc_nop_release(struct device *dev) > +static void usb_gadget_release(struct device *dev) > { > + struct usb_gadget *gadget; > + > dev_vdbg(dev, "%s\n", __func__); > + > + gadget = container_of(dev, struct usb_gadget, dev); > + complete(&gadget->done); > + memset(dev, 0x0, sizeof(*dev)); No, the memory should be freed here, not memset. thanks, greg k-h