From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759574AbYDKJH5 (ORCPT ); Fri, 11 Apr 2008 05:07:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758251AbYDKJHt (ORCPT ); Fri, 11 Apr 2008 05:07:49 -0400 Received: from mail29.messagelabs.com ([216.82.249.147]:42469 "HELO mail29.messagelabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1758159AbYDKJHs (ORCPT ); Fri, 11 Apr 2008 05:07:48 -0400 X-VirusChecked: Checked X-Env-Sender: Uwe.Kleine-Koenig@digi.com X-Msg-Ref: server-4.tower-29.messagelabs.com!1207904868!10609077!1 X-StarScan-Version: 5.5.12.14.2; banners=-,-,- X-Originating-IP: [66.77.174.21] Date: Fri, 11 Apr 2008 11:07:39 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: "Hans J. Koch" Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: [PATCH 1/4 v2] UIO: hold a reference to the device's owner while the device is open Message-ID: <20080411090739.GA31625@digi.com> References: <1207831023-8583-1-git-send-email-Uwe.Kleine-Koenig@digi.com> <1207831023-8583-2-git-send-email-Uwe.Kleine-Koenig@digi.com> <20080410210229.GF3193@local> <20080411065027.GB18096@digi.com> <20080411084454.GA3185@local> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20080411084454.GA3185@local> User-Agent: Mutt/1.5.13 (2006-08-11) X-OriginalArrivalTime: 11 Apr 2008 09:07:40.0107 (UTC) FILETIME=[7E55E9B0:01C89BB3] X-TM-AS-Product-Ver: SMEX-8.0.0.1181-5.000.1023-15842.003 X-TM-AS-Result: No--14.197000-8.000000-31 X-TM-AS-User-Approved-Sender: No X-TM-AS-User-Blocked-Sender: No Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Otherwise the device might just disappear while /dev/uioX is being used which results in an Oops. Signed-off-by: Uwe Kleine-König --- Hans J. Koch wrote: > > > The label err_module_get should probably be omitted because it's used only > > > once and has just one line of code. You could simply write "return ret" > > > instead of "goto err_module_get". > > This makes code shuffling easier. For example if someone decides that > > try_module_get should be done after allocating listener then you only > > have to exchange the two corresponding code blocks and the two groups > > (label + cleanup) in the error handling block. > > If the error handling is spread over the whole functions you can easily > > miss something---as happend above. :-) > > Well, it depends. It's all about readability. Any function should be > written in a way that makes it as clear as possible what it does. Your > code is certainly not critical regarding that aspect, but I think it can > still be improved. And a label that is used only once and contains only > one line of code is definetly unnecessary. I don't follow the > maybe-one-day-in-the-future-it-might-be-useful philosophy. I like code > that is as clean and readable as possible _now_. That thing about code reordering is minor compared to having all error handling in one place, but ... > And as this patch is > not just a driver but affects the UIO core, this is even more important. > > Could you please send an updated patch? ... , it's your code, so you can find a new version below. Best regards Uwe drivers/uio/uio.c | 36 +++++++++++++++++++++--------------- 1 files changed, 21 insertions(+), 15 deletions(-) diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index 1175908..55cc7b8 100644 --- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -301,23 +301,33 @@ static int uio_open(struct inode *inode, struct file *filep) if (!idev) return -ENODEV; + if (!try_module_get(idev->owner)) + return -ENODEV; + listener = kmalloc(sizeof(*listener), GFP_KERNEL); - if (!listener) - return -ENOMEM; + if (!listener) { + ret = -ENOMEM; + goto err_alloc_listener; + } listener->dev = idev; listener->event_count = atomic_read(&idev->event); filep->private_data = listener; if (idev->info->open) { - if (!try_module_get(idev->owner)) - return -ENODEV; ret = idev->info->open(idev->info, inode); - module_put(idev->owner); + if (ret) + goto err_infoopen; } - if (ret) - kfree(listener); + return 0; + +err_infoopen: + + kfree(listener); +err_alloc_listener: + + module_put(idev->owner); return ret; } @@ -336,12 +346,11 @@ static int uio_release(struct inode *inode, struct file *filep) struct uio_listener *listener = filep->private_data; struct uio_device *idev = listener->dev; - if (idev->info->release) { - if (!try_module_get(idev->owner)) - return -ENODEV; + if (idev->info->release) ret = idev->info->release(idev->info, inode); - module_put(idev->owner); - } + + module_put(idev->owner); + if (filep->f_flags & FASYNC) ret = uio_fasync(-1, filep, 0); kfree(listener); @@ -510,10 +519,7 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma) return -EINVAL; if (idev->info->mmap) { - if (!try_module_get(idev->owner)) - return -ENODEV; ret = idev->info->mmap(idev->info, vma); - module_put(idev->owner); return ret; } -- 1.5.4.5 -- Uwe Kleine-König, Software Engineer Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962