Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751447AbbLUMOp (ORCPT ); Mon, 21 Dec 2015 07:14:45 -0500 Received: from lists.s-osg.org ([54.187.51.154]:59738 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751219AbbLUMOo (ORCPT ); Mon, 21 Dec 2015 07:14:44 -0500 Subject: Re: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered To: Mauro Carvalho Chehab , Shuah Khan References: <1449874629-8973-1-git-send-email-javier@osg.samsung.com> <1449874629-8973-2-git-send-email-javier@osg.samsung.com> <566B5DFB.3020100@osg.samsung.com> <20151215084153.1f54d561@recife.lan> From: Javier Martinez Canillas X-Enigmail-Draft-Status: N1110 Cc: linux-kernel@vger.kernel.org, Sakari Ailus , Laurent Pinchart , Hans Verkuil , linux-media@vger.kernel.org Message-ID: <5677ED2D.2040708@osg.samsung.com> Date: Mon, 21 Dec 2015 09:14:37 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151215084153.1f54d561@recife.lan> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3500 Lines: 95 Hello Mauro, On 12/15/2015 07:41 AM, Mauro Carvalho Chehab wrote: > Em Fri, 11 Dec 2015 16:36:27 -0700 > Shuah Khan escreveu: > >> On 12/11/2015 03:57 PM, Javier Martinez Canillas wrote: >>> Most media functions that unregister, check if the corresponding register >>> function succeed before. So these functions can safely be called even if a >>> registration was never made or the component as already been unregistered. >>> >>> Add the same check to media_device_unregister() function for consistency. >>> >>> This will also allow to split the media_device_register() function in an >>> initialization and registration functions without the need to change the >>> generic cleanup functions and error code paths for all the media drivers. >>> >>> Suggested-by: Sakari Ailus >>> Signed-off-by: Javier Martinez Canillas >>> Acked-by: Sakari Ailus >>> >>> --- >>> >>> Changes in v5: None >>> Changes in v4: None >>> Changes in v3: None >>> Changes in v2: >>> - Reword the documentation for media_device_unregister(). Suggested by Sakari. >>> - Added Sakari's Acked-by tag for patch #1. >>> >>> drivers/media/media-device.c | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c >>> index c12481c753a0..11c1c7383361 100644 >>> --- a/drivers/media/media-device.c >>> +++ b/drivers/media/media-device.c >>> @@ -577,6 +577,8 @@ EXPORT_SYMBOL_GPL(__media_device_register); >>> * media_device_unregister - unregister a media device >>> * @mdev: The media device >>> * >>> + * It is safe to call this function on an unregistered >>> + * (but initialised) media device. >>> */ >>> void media_device_unregister(struct media_device *mdev) >>> { >>> @@ -584,6 +586,10 @@ void media_device_unregister(struct media_device *mdev) >>> struct media_entity *next; >>> struct media_interface *intf, *tmp_intf; >>> >>> + /* Check if mdev was ever registered at all */ >>> + if (!media_devnode_is_registered(&mdev->devnode)) >>> + return; >> >> This is a good check, however, this check will not prevent >> media_device_unregister() from getting run twice by two >> different drivers. i.e media_devnode gets unregistered >> towards the end of at the end of media_device_unregister(). >> >> In an example case, if bridge driver and snd-usb-aduio both >> call media_device_unregister(), this check won't help prevent >> media_device_unregister() being done only once. I think we >> need a different state variable in struct media_device >> to ensure unregister is done only once. > > True. We need move the spin_lock() code to be called before > calling media_device_is_registered(). > I see, the check in $SUBJECT was to avoid each driver to have a similar check for cleanup in its error path but I didn't take into account the fact that two drivers may share the same struct media_device, as you explained to me is the case for ALSA and V4L2 MC integration. > I'm sending such patches. > Thanks, I'll review and test them. > Thanks for reporting it. > > Regards, > Mauro > Best regards, -- Javier Martinez Canillas Open Source Group Samsung Research America -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/