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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 F3A7AC433DF for ; Sat, 30 May 2020 15:25:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CCE1720723 for ; Sat, 30 May 2020 15:25:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728999AbgE3PZY (ORCPT ); Sat, 30 May 2020 11:25:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:47180 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728989AbgE3PZY (ORCPT ); Sat, 30 May 2020 11:25:24 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id A632BAE72; Sat, 30 May 2020 15:25:22 +0000 (UTC) Message-ID: <1590852311.14886.3.camel@suse.com> Subject: Re: [PATCH] USB: cdc-wdm: Call wake_up_all() when clearing WDM_IN_USE bit. From: Oliver Neukum To: Alan Stern , Andrey Konovalov Cc: Tetsuo Handa , Greg Kroah-Hartman , Colin Ian King , Arnd Bergmann , USB list , syzbot , syzkaller-bugs Date: Sat, 30 May 2020 17:25:11 +0200 In-Reply-To: <20200528205807.GB21709@rowland.harvard.edu> References: <1590134662.19681.12.camel@suse.com> <03894591-a1ac-496a-a35f-55953e5bcc06@i-love.sakura.ne.jp> <1590408381.2838.4.camel@suse.com> <4a686d9a-d09f-44f3-553c-bcf0bd8a8ea1@i-love.sakura.ne.jp> <082ae642-0703-6c26-39f6-d725e395ef9a@i-love.sakura.ne.jp> <27b7545e-8f41-10b8-7c02-e35a08eb1611@i-love.sakura.ne.jp> <20200528194057.GA21709@rowland.harvard.edu> <20200528205807.GB21709@rowland.harvard.edu> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Am Donnerstag, den 28.05.2020, 16:58 -0400 schrieb Alan Stern: > On Thu, May 28, 2020 at 09:51:35PM +0200, Andrey Konovalov wrote: > > > I don't understand what the problem is. Can you explain in more general > > > terms -- nothing specific to wdm or anything like that -- what you are > > > concerned about? Is this something that could happen to any gadget > > > driver? Or any USB class device driver? Or does it only affect > > > usespace components of raw-gadget drivers? > > > > So, AFAIU, we have a driver whose flush() callback blocks on > > wait_event(), which can only terminate when either 1) the driver > > receives a particular USB response from the device or 2) the device > > disconnects. > > This sounds like a bug in the driver. What would it do if someone had a Arguably yes. I will introduce a timeout. Unfortunately flush() requires a non-interruptible sleep, as you cannot sanely return EAGAIN. Regards Oliver