linux-kernel - Re: [PATCH v3 1/3] rpmsg: char: Remove put_device() in rpmsg_eptdev

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Message-ID: <b754155b-a17b-4e8e-92b7-8ab37949dded@oss.qualcomm.com>
Date: Fri, 14 Nov 2025 17:53:14 +0800
From: Zhongqiu Han <zhongqiu.han@....qualcomm.com>
To: Dawei Li <dawei.li@...ux.dev>, andersson@...nel.org,
        mathieu.poirier@...aro.org
Cc: linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        set_pte_at@...look.com, stable@...r.kernel.org,
        zhongqiu.han@....qualcomm.com
Subject: Re: [PATCH v3 1/3] rpmsg: char: Remove put_device() in
 rpmsg_eptdev_add()

On 11/13/2025 11:39 PM, Dawei Li wrote:
> put_device() is called on error path of rpmsg_eptdev_add() to cleanup
> resource attached to eptdev->dev, unfortunately it's bogus cause
> dev->release() is not set yet.
> 
> When a struct device instance is destroyed, driver core framework checks
> the possible release() callback from candidates below:
> - struct device::release()
> - dev->type->release()
> - dev->class->dev_release()
> 
> Rpmsg eptdev owns none of them so WARN() will complaint the absence of
> release():

Hi Dawei,


> 
> [  159.112182] ------------[ cut here ]------------
> [  159.112188] Device '(null)' does not have a release() function, it is broken and must be fixed. See Documentation/core-api/kobject.rst.
> [  159.112205] WARNING: CPU: 2 PID: 1975 at drivers/base/core.c:2567 device_release+0x7a/0x90
> 


Although my local checkpatch.pl didn’t complain about this log line
exceeding 75 characters, could we simplify it or just provide a summary
instead?


> Fixes: c0cdc19f84a4 ("rpmsg: Driver for user space endpoint interface")
> Cc: stable@...r.kernel.org
> Signed-off-by: Dawei Li <dawei.li@...ux.dev>
> ---
>   drivers/rpmsg/rpmsg_char.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index 34b35ea74aab..1b8297b373f0 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -494,7 +494,6 @@ static int rpmsg_eptdev_add(struct rpmsg_eptdev *eptdev,
>   	if (cdev)
>   		ida_free(&rpmsg_minor_ida, MINOR(dev->devt));
>   free_eptdev:
> -	put_device(dev);


Yes, remove put_device can solve the warning issue, however it would
introduce one memleak issue of kobj->name.

https://git.kernel.org/pub/scm/linux/kernel/git/remoteproc/linux.git/tree/drivers/rpmsg/rpmsg_char.c#n381 


dev_set_name(dev, "rpmsg%d", ret); is already called, it depends on
put_device to free memory, right?


>   	kfree(eptdev);
>   
>   	return ret;


-- 
Thx and BRs,
Zhongqiu Han