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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 1BE6CC49361 for ; Mon, 21 Jun 2021 01:37:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0E8C61206 for ; Mon, 21 Jun 2021 01:37:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230032AbhFUBkE (ORCPT ); Sun, 20 Jun 2021 21:40:04 -0400 Received: from so254-9.mailgun.net ([198.61.254.9]:50301 "EHLO so254-9.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229899AbhFUBkD (ORCPT ); Sun, 20 Jun 2021 21:40:03 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1624239470; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=lYEMqrykgWc6HM062opojkGd6Q6iRcgqfcdWknEUeUY=; b=Oo7904a39D9DiVXHPDw6yG6zMumTxDglJqAud3HJj7GiF7unYDBbwOki5ym/nK9KaC8qmzvh pHjdNy9/LS/LQeYGETbxm1gi5SnAs1QRLbzNOQk9sCmZ4ITC7TzbQw5KQsgGAWFG9UGLm9zm vVcRencTqyZ54O5ddaJ+AL/mBxo= X-Mailgun-Sending-Ip: 198.61.254.9 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-n04.prod.us-west-2.postgun.com with SMTP id 60cfed5fe570c056194d4f81 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 21 Jun 2021 01:37:35 GMT Sender: linyyuan=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id CAFB3C43217; Mon, 21 Jun 2021 01:37:35 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: linyyuan) by smtp.codeaurora.org (Postfix) with ESMTPSA id EA65EC433F1; Mon, 21 Jun 2021 01:37:34 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 21 Jun 2021 09:37:34 +0800 From: linyyuan@codeaurora.org To: Alan Stern Cc: Felipe Balbi , Thinh Nguyen , Greg Kroah-Hartman , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Jack Pham Subject: Re: [PATCH v3 1/2] usb: udc: core: hide struct usb_gadget_driver to gadget driver In-Reply-To: <20210620134743.GA377492@rowland.harvard.edu> References: <20210619154309.52127-1-linyyuan@codeaurora.org> <20210619154309.52127-2-linyyuan@codeaurora.org> <20210620021337.GA361976@rowland.harvard.edu> <42b3ebc2316495328e2d0061af81ef17@codeaurora.org> <018a4e222c2c3d6f5ca63b5f2036f8d8@codeaurora.org> <20210620134743.GA377492@rowland.harvard.edu> Message-ID: <98c2729c25442d6c66131d17cabdda27@codeaurora.org> X-Sender: linyyuan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-06-20 21:47, Alan Stern wrote: > On Sun, Jun 20, 2021 at 11:53:18AM +0800, linyyuan@codeaurora.org > wrote: >> On 2021-06-20 11:46, linyyuan@codeaurora.org wrote: >> > On 2021-06-20 10:13, Alan Stern wrote: >> > > On Sat, Jun 19, 2021 at 11:43:08PM +0800, Linyu Yuan wrote: >> > > > currently most gadget driver have a pointer to save >> > > > struct usb_gadget_driver from upper layer, >> > > > it allow upper layer set and unset of the pointer. >> > > > >> > > > there is race that upper layer unset the pointer first, >> > > > but gadget driver use the pointer later, >> > > > and it cause system crash due to NULL pointer access. >> > > >> > > This race has already been fixed in Greg's usb-next branch. See >> > > commit >> > > 7dc0c55e9f30 ("USB: UDC core: Add udc_async_callbacks gadget op") and >> > > following commits 04145a03db9d ("USB: UDC: Implement >> > > udc_async_callbacks in dummy-hcd") and b42e8090ba93 ("USB: UDC: >> > > Implement udc_async_callbacks in net2280"). >> > > >> > thanks, this is better, lower driver only need change several places. >> > > You just need to write a corresponding patch implementing the >> > > async_callbacks op for dwc3. >> > yes, i will do. >> > > >> Alan, i want to discuss your suggestion again in b42e8090ba93 ("USB: >> UDC: >> Implement udc_async_callbacks in net2280") >> >> + if (dev->async_callbacks) { ----> if CPU1 saw >> this >> is true >> + spin_unlock(&dev->lock); ---> CPU2 get >> lock >> after this unlock, >> it will set async_callbacks to false, then follow call also crash, >> right ? >> + tmp = dev->driver->setup(&dev->gadget, >> &u.r); >> + spin_lock(&dev->lock); >> + } > > No, this is okay. The reason is because usb_gadget_remove_driver (CPU2 > in your example) does this: > > usb_gadget_disable_async_callbacks(udc); > if (udc->gadget->irq) > synchronize_irq(udc->gadget->irq); > udc->driver->unbind(udc->gadget); > usb_gadget_udc_stop(udc); > > The synchronize_irq call will make CPU2 wait until CPU1 has finished > handling the interrupt for the setup packet. The system won't crash, > because dev->driver->setup will be called before unbind and udc_stop > instead of after. still several question, 1. how about suspend calll dev->driver->suspend ? 2. will 04145a03db9d ("USB: UDC: Implement udc_async_callbacks in dummy-hcd") backport to LTS branch ? 3. how about coding style ? so following code if (foo->gadget_driver && foo->gadget_driver->resume) change to if (foo->asnyc_callbacks && foo->gadget_driver->resume) > > Alan Stern