linux-kernel - Re: [RFC PATCH 1/4] media: Add Media Device Allocator API

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Date:	Sat, 26 Mar 2016 05:50:22 -0700
From:	Joe Perches <joe@...ches.com>
To:	Shuah Khan <shuahkh@....samsung.com>,
	laurent.pinchart@...asonboard.com, mchehab@....samsung.com,
	perex@...ex.cz, tiwai@...e.com, hans.verkuil@...co.com,
	chehabrafael@...il.com, javier@....samsung.com,
	jh1009.sung@...sung.com
Cc:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	alsa-devel@...a-project.org
Subject: Re: [RFC PATCH 1/4] media: Add Media Device Allocator API

On Fri, 2016-03-25 at 22:38 -0600, Shuah Khan wrote:
> Add Media Device Allocator API to manage Media Device life time problems.
> There are known problems with media device life time management. When media
> device is released while an media ioctl is in progress, ioctls fail with
> use-after-free errors and kernel hangs in some cases.

Seems reasonable, thanks.

trivial:

> diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c
[]
> +static struct media_device *__media_device_get(struct device *dev,
> +					       bool alloc, bool kref)
> +{
[]
> +	pr_info("%s: mdev=%p\n", __func__, &mdi->mdev);

All of the pr_info uses here seem like debugging
and should likely be pr_debug instead.
> +struct media_device *media_device_find(struct device *dev)
> +{
> +	pr_info("%s\n", __func__);

These seem like function tracing and maybe could/should
use ftrace instead.
+/* don't allocate - increment kref if one is found */
> +struct media_device *media_device_get_ref(struct device *dev)
> +{
> +	pr_info("%s\n", __func__);