From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3AE3614E2C0; Thu, 28 Nov 2024 21:47:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732830461; cv=none; b=E84+N68mUu25HJVvB68wNO1lq1tIhLQK1b6d8Yhk2WCxEug9EvoLxhgckZz0Onq/eWPV1vJ3Uzb3hdAI+CK4X58ifenThGSvSuq6bJYbQc15VsMbPk6ILVjddb+QfdTtRnFPLhKcH0Aava8Gow6/xfSKv8XmqLq6PVmUMth+CxM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732830461; c=relaxed/simple; bh=DnxXmwuKXAMM+BS6t+coUEjPdZAEYERTEen8ITrr53U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TdrO51UE+AFr/RNKH6oRmILiuaxPyuQ61AupKABl3YlFH0nCZyulQsm7kuT1Ia0EFpM8Yh+qShfBq5sP4BRi2Y5CalSFVYtSucg5+dHZs1Zd4z/ONvZp4ZO46uwrTpGLAwW/C7L3oFir2IriYMQab4JYbG8JplEzJ2FL6eEW9n0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=Fhs54yuY; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="Fhs54yuY" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 80857526; Thu, 28 Nov 2024 22:47:14 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1732830434; bh=DnxXmwuKXAMM+BS6t+coUEjPdZAEYERTEen8ITrr53U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Fhs54yuYa4lHFkwYCspf0NQK0zntgSLbxFfWQHINNxvV/5qtPTkWw1OSgOtvWOp/I 70x29L0lkY9uTB9CpJOAPL7NLp4quX9VsoFq9Msh9oQlGzR9ShuaBr6xRAI3joLSYd slAfUDGBXS4O4kz1JICXNFsxDRPEzcQYwkhKBmnA= Date: Thu, 28 Nov 2024 23:47:27 +0200 From: Laurent Pinchart To: Ricardo Ribalda Cc: Hans de Goede , Mauro Carvalho Chehab , Guennadi Liakhovetski , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/4] media: uvcvideo: Remove redundant NULL assignment Message-ID: <20241128214727.GE25839@pendragon.ideasonboard.com> References: <20241127-uvc-fix-async-v2-0-510aab9570dd@chromium.org> <20241127-uvc-fix-async-v2-4-510aab9570dd@chromium.org> <20241128212628.GD25731@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Thu, Nov 28, 2024 at 10:34:38PM +0100, Ricardo Ribalda wrote: > On Thu, 28 Nov 2024 at 22:26, Laurent Pinchart wrote: > > On Wed, Nov 27, 2024 at 12:14:52PM +0000, Ricardo Ribalda wrote: > > > ctrl->handle will only be different than NULL for controls that have > > > mappings. This is because that assignment is only done inside > > > uvc_ctrl_set() for mapped controls. > > > > That seems right. I checked the unplug paths, and the mappings are > > destroyed from uvc_delete(), after all file handles get closed. > > > > I think this patch should go first in the series, as otherwise there's a > > temporary state where you rely on handle never being touched without > > holding the proper lock, and this code path violates that requirement. > > Is there anything I may be missing that would cause issues with > > bisection if I move this patch at the beginning of the series ? > > You probably want to add the Cc: stable and Fixes: tags if you make > this patch the first one. Good point. Given that ctrl->handle for controls without mappings can't be touched anywhere else, I think it's safe to keep this patch last, and not backport it. There may be a theoretical issue with mappings dynamically added at runtime, as the list could then become non-empty and the condition change, but the condition should never turn from false to true, only from true to false, so I think it's safe. I'll keep the patch last. > > > Signed-off-by: Ricardo Ribalda > > > > Reviewed-by: Laurent Pinchart > > > > > --- > > > drivers/media/usb/uvc/uvc_ctrl.c | 4 +--- > > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c > > > index 99ddc5e9dff8..b9c9ff629ab6 100644 > > > --- a/drivers/media/usb/uvc/uvc_ctrl.c > > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c > > > @@ -1645,10 +1645,8 @@ bool uvc_ctrl_status_event_async(struct urb *urb, struct uvc_video_chain *chain, > > > struct uvc_device *dev = chain->dev; > > > struct uvc_ctrl_work *w = &dev->async_ctrl; > > > > > > - if (list_empty(&ctrl->info.mappings)) { > > > - ctrl->handle = NULL; > > > + if (list_empty(&ctrl->info.mappings)) > > > return false; > > > - } > > > > > > w->data = data; > > > w->urb = urb; -- Regards, Laurent Pinchart