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=-9.0 required=3.0 tests=BAYES_00,INCLUDES_PATCH, MAILING_LIST_MULTI,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 EA85AC433E0 for ; Thu, 18 Feb 2021 10:18:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 98F1F64E68 for ; Thu, 18 Feb 2021 10:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232362AbhBRKFj (ORCPT ); Thu, 18 Feb 2021 05:05:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:47078 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231280AbhBRIz4 (ORCPT ); Thu, 18 Feb 2021 03:55:56 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (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 79EBF64E6F; Thu, 18 Feb 2021 08:47:18 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1lCexv-00EjMV-TI; Thu, 18 Feb 2021 08:47:16 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 18 Feb 2021 08:47:15 +0000 From: Marc Zyngier To: Greg KH Cc: Michael Walle , linux-kernel@vger.kernel.org, tglx@linutronix.de Subject: Re: [PATCH] irqdomain: remove debugfs_file from struct irq_domain In-Reply-To: References: <20210217195717.13727-1-michael@walle.cc> <4e4d0479b935e60a53f75ef534086476@kernel.org> <5c527bfb6f3dfe31b5c25f29418306c6@walle.cc> <87czwys6s1.wl-maz@kernel.org> <8b4de9eae773a43b38f42c8ab6d9d23c@walle.cc> User-Agent: Roundcube Webmail/1.4.11 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: gregkh@linuxfoundation.org, michael@walle.cc, linux-kernel@vger.kernel.org, tglx@linutronix.de X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-02-18 08:38, Greg KH wrote: > On Thu, Feb 18, 2021 at 09:27:09AM +0100, Michael Walle wrote: >> Am 2021-02-18 08:31, schrieb Greg KH: >> > On Wed, Feb 17, 2021 at 09:50:38PM +0000, Marc Zyngier wrote: >> > > On Wed, 17 Feb 2021 20:10:50 +0000, >> > > Michael Walle wrote: >> > > > >> > > > Am 2021-02-17 21:02, schrieb Marc Zyngier: >> > > > > On 2021-02-17 19:57, Michael Walle wrote: >> > > > >> Hi Greg, >> > > > >> >> > > > >>> There's no need to keep around a dentry pointer to a simple file that >> > > > >>> debugfs itself can look up when we need to remove it from the system. >> > > > >>> So simplify the code by deleting the variable and cleaning up the >> > > > >>> logic >> > > > >>> around the debugfs file. >> > > > >> >> > > > >> This will generate the following oops on my board (arm64, >> > > > >> freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts). In debugfs_lookup() >> > > > >> debugfs_mount is NULL. >> > > > > >> > > > > That's odd. I gave it a go yesterday, and nothing blew up. >> > > > > Which makes me wonder whether I had the debug stuff enabled >> > > > > the first place... >> > > > > >> > > > > I've dropped the patch from -next for now until I figure it out >> > > > > (probably tomorrow). >> > > > >> > > > Mh, maybe its my .config, I've attached it. I also noticed that >> > > > the board boots just fine in our kernel-ci [1]. >> > > >> > > I reproduced here. I had disabled GENERIC_IRQ_DEBUGFS for obscure >> > > reasons, and it caught fire as I re-enabled it. >> > > >> > > Adding this fixes it for me: >> > > >> > > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c >> > > index 367ff1c35f75..d8a14cf1a7b6 100644 >> > > --- a/kernel/irq/irqdomain.c >> > > +++ b/kernel/irq/irqdomain.c >> > > @@ -1904,7 +1904,8 @@ static void debugfs_add_domain_dir(struct >> > > irq_domain *d) >> > > >> > > static void debugfs_remove_domain_dir(struct irq_domain *d) >> > > { >> > > - debugfs_remove(debugfs_lookup(d->name, domain_dir)); >> > > + if (domain_dir) >> > > + debugfs_remove(debugfs_lookup(d->name, domain_dir)); >> > > } >> > > >> > > void __init irq_domain_debugfs_init(struct dentry *root) >> > > >> > > >> > > Could you please check whether it works for you? >> > >> > Can you try this debugfs core change instead? Callers to debugfs should >> > not have to do the above type of checking as debugfs should be much more >> > robust than that. >> > >> > thanks, >> > >> > greg k-h >> > >> > >> > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c >> > index 2fcf66473436..5aa798f52b6e 100644 >> > --- a/fs/debugfs/inode.c >> > +++ b/fs/debugfs/inode.c >> > @@ -297,7 +297,7 @@ struct dentry *debugfs_lookup(const char *name, >> > struct dentry *parent) >> > { >> > struct dentry *dentry; >> > >> > - if (IS_ERR(parent)) >> > + if (IS_ERR_OR_NULL(name) || IS_ERR(parent)) >> > return NULL; >> > >> > if (!parent) >> >> This doesn't work. name is not NULL when it is called. > > Ok, but it is a good check we need to make anyway, I'll add it to a > patch series :) > >> What has to happen before debugfs_lookup() can be called? Looks like >> someone has to initialize the static debugfs_mount, first. > > Wow, wait, you are removing a debugfs file _before_ debugfs is even > initialized? Didn't expect that, ok, let me go try this again... Yeah, that's a poor man's rename (file being deleted and re-created). M. -- Jazz is not dead. It just smells funny...