From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753883Ab0C2VSZ (ORCPT ); Mon, 29 Mar 2010 17:18:25 -0400 Received: from moutng.kundenserver.de ([212.227.126.187]:64916 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752768Ab0C2VSY (ORCPT ); Mon, 29 Mar 2010 17:18:24 -0400 From: Arnd Bergmann To: Frederic Weisbecker Subject: Re: [GIT, RFC] Killing the Big Kernel Lock Date: Mon, 29 Mar 2010 23:18:09 +0200 User-Agent: KMail/1.13.1 (Linux/2.6.33-00063-g0795fff; KDE/4.4.1; x86_64; ; ) Cc: linux-kernel@vger.kernel.org, Matthew Wilcox , Thomas Gleixner , jblunck@suse.de, Alan Cox , Ingo Molnar References: <201003242240.54907.arnd@arndb.de> <201003291304.24629.arnd@arndb.de> <20100329175935.GD5101@nowhere> In-Reply-To: <20100329175935.GD5101@nowhere> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201003292318.10212.arnd@arndb.de> X-Provags-ID: V01U2FsdGVkX1+XsMCERTghpWUs3A1h8dHwo2vNQvUekIH4QMF 7YI7D20YW4xhjt+73QNteHiNWovVBjjFAG0pNPScAuCPQzdO3P u5ol/81gUcdHsVHH15dTQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 29 March 2010 19:59:39 Frederic Weisbecker wrote: > On Mon, Mar 29, 2010 at 12:04:24PM +0100, Arnd Bergmann wrote: > > On Monday 29 March 2010, Frederic Weisbecker wrote: > > > On Mon, Mar 29, 2010 at 01:18:48AM +0200, Frederic Weisbecker wrote: > > > > @@ -1943,7 +1949,7 @@ static ssize_t proc_fdinfo_read(struct file *file, char __user *buf, > > > > } > > > > > > > > static const struct file_operations proc_fdinfo_file_operations = { > > > > - .open = nonseekable_open, > > > > + .llseek = generic_file_llseek, > > > > .read = proc_fdinfo_read, > > > > }; > > > > > > > > > > > > Replacing default_llseek() by generic_file_llseek() as you > > > > did for most of the other parts is fine. > > > > > > > > But the above changes the semantics as it makes it seekable. > > > > Why not just keeping it as is? It just ends up in no_llseek(). > > > > The default is default_llseek, which uses the BKL and cannot be > > used if procfs is builtin and the BKL is a module. > > Yeah, but you removed the nonseekable_open and made generic_file_llseek > in llseek on this one. > This makes it seekable while it wasn't, changing its ABI. > It wasn't taking the bkl before that as it was calling > no_llseek(). Ah, I see what you mean. That change was certainly not intentional an should be reverted. Thanks for pointing this out. > > The BKL in procfs is only for proc files that have registered > > their own .ioctl instead of .unlocked_ioctl method. Converting > > every file_operations instance to provide an unlocked_ioctl > > (as one of the other patches does) makes sure that this path > > is never taken. BTW, there are less than a handful of procfs files > > that provide an ioctl operation, and those probably should never > > have been merged. > > > There are three of them. I'm going to make them .unlocked_ioctl > and push the bkl inside, and warn on further uses of .ioctl, > without applying the bkl there anymore. > > That plus your bkl removal in proc seek, should totally remove the > bkl from procfs. Ok Arnd