linux-kernel - Re: [PATCH 1/2] kobject: don't delay to cleanup module kobject

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Date:   Fri, 26 Nov 2021 17:08:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Petr Mladek <pmladek@...e.com>, linux-kernel@...r.kernel.org,
        Luis Chamberlain <mcgrof@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>
Subject: Re: [PATCH 1/2] kobject: don't delay to cleanup module kobject

On Fri, Nov 05, 2021 at 02:37:09PM +0800, Ming Lei wrote:
> CONFIG_DEBUG_KOBJECT_RELEASE is used for debugging kobject release/cleanup
> issue. The module kobject is released after module_exit() returns. If
> this kobject is delayed too much, and may cause other kobject's
> cleaned up a bit earlier before freeing module, then real issue is
> hidden.
> 
> So don't delay module kobject's cleanup, meantime module kobject is
> always cleaned up synchronously, and we needn't module kobject's
> cleanup.
> 
> Signed-off-by: Ming Lei <ming.lei@...hat.com>
> ---
>  lib/kobject.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/lib/kobject.c b/lib/kobject.c
> index ea53b30cf483..4c0dbe11be3d 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -16,6 +16,7 @@
>  #include <linux/stat.h>
>  #include <linux/slab.h>
>  #include <linux/random.h>
> +#include <linux/module.h>
>  
>  /**
>   * kobject_namespace() - Return @kobj's namespace tag.
> @@ -727,6 +728,10 @@ static void kobject_release(struct kref *kref)
>  	struct kobject *kobj = container_of(kref, struct kobject, kref);
>  #ifdef CONFIG_DEBUG_KOBJECT_RELEASE
>  	unsigned long delay = HZ + HZ * (get_random_int() & 0x3);
> +
> +	if (kobj->ktype == &module_ktype)
> +		delay = 0;

No, there should not be anything "special" about module kobjects to get
this kind of treatment.  They should work like any other kobject and
clean up properly when needed.

thanks,

greg k-h