From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753247AbcLJNEG (ORCPT ); Sat, 10 Dec 2016 08:04:06 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49536 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752078AbcLJNEF (ORCPT ); Sat, 10 Dec 2016 08:04:05 -0500 Date: Sat, 10 Dec 2016 14:04:04 +0100 From: Greg Kroah-Hartman To: Vladimir Zapolskiy Cc: Rob Herring , linux-kernel@vger.kernel.org Subject: Re: [PATCH] driver core: flush async calls before testing driver removal Message-ID: <20161210130404.GB8145@kroah.com> References: <20161210001519.24870-1-vz@mleia.com> <20161210073245.GA19610@kroah.com> <4c1eb9e4-3e49-660a-e3c2-d048d3189a26@mleia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4c1eb9e4-3e49-660a-e3c2-d048d3189a26@mleia.com> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 10, 2016 at 02:38:41PM +0200, Vladimir Zapolskiy wrote: > Hello Greg, > > On 12/10/2016 09:32 AM, Greg Kroah-Hartman wrote: > > On Sat, Dec 10, 2016 at 02:15:19AM +0200, Vladimir Zapolskiy wrote: > >> If CONFIG_DEBUG_TEST_DRIVER_REMOVE option is enabled a number of false > >> positives are reported for ATA controller drivers, because ATA port > >> probes are done asynchronously, and the same problem may also touch > >> other asynchronously probed drivers. > >> > >> To reduce the rate of false reports on boot call async_synchronize_full() > >> before attempting to remove a driver, the same is done in delete_module() > >> syscall for all possible drivers and in __device_release_driver() function > >> for asynchronously probed drivers. > > > > __device_release_driver() already calls this function, why call it > > again? > > > > __device_release_driver() is not called on test removal of drivers, if > CONFIG_DEBUG_TEST_DRIVER_REMOVE option is enabled. > > This opens a possibility to races like one I've discovered: > > https://www.spinics.net/lists/linux-ide/msg53473.html > > Next, async_synchronize_full() from __device_release_driver() is not > called in case of removal of ATA controller drivers, because > driver_allows_async_probing(drv) return value is false. Hm, how does this not also get hit if you unbind/bind/unbind/bind/etc. from userspace as well? I don't think this is a CONFIG_DEBUG_TEST_DRIVER_REMOVE issue, but just that this option finds the problem corner cases as you are finding out :) thanks, greg k-h