linux-kernel - Re: [PATCH] debugobjects: Print object pointer in debug_print

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Date:   Tue, 4 Oct 2022 15:58:17 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH] debugobjects: Print object pointer in
 debug_print_object()

On Thu, May 19, 2022 at 01:22:01PM -0700, Stephen Boyd wrote:
> Delayed kobject debugging (CONFIG_DEBUG_KOBJECT_RELEASE) prints the
> kobject pointer that's being released in kobject_release() before
> scheduling a randomly delayed work to do the actual release work. If the
> caller of kobject_put() frees the kobject upon return then we'll
> typically see a debugobject warning about freeing an active timer.
> Usually the release function is the function that does the kfree() of
> the struct containing the kobject.
> 
> For example the following print is seen
> 
>  kobject: 'queue' (ffff888114236190): kobject_release, parent 0000000000000000 (delayed 1000)
>  ------------[ cut here ]------------
>  ODEBUG: free active (active state 0) object type: timer_list hint: kobject_delayed_cleanup+0x0/0x390
> 
> but we can't match up the kobject printk with the debug object printk
> because it could be any number of kobjects that was released around that
> time. The random delay for the work doesn't help either.
> 
> Print the address of the object being tracked to help us figure out
> which kobject is the problem here. Note that we don't use %px here to
> match the other %p usage in debugobject debugging. Due to %p usage we'll
> have to disable pointer hashing to correlate the two pointer printks.
> 
> Cc: Guenter Roeck <groeck@...omium.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>

Did this patch get lost, or was it rejected ? I don't see a reply,
and it has not been applied.

FWIW:

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

Thanks,
Guenter

> ---
>  lib/debugobjects.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> index 6946f8e204e3..a1c987e967e0 100644
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -503,9 +503,9 @@ static void debug_print_object(struct debug_obj *obj, char *msg)
>  			descr->debug_hint(obj->object) : NULL;
>  		limit++;
>  		WARN(1, KERN_ERR "ODEBUG: %s %s (active state %u) "
> -				 "object type: %s hint: %pS\n",
> +				 "object: %p object type: %s hint: %pS\n",
>  			msg, obj_states[obj->state], obj->astate,
> -			descr->name, hint);
> +			obj->object, descr->name, hint);
>  	}
>  	debug_objects_warnings++;
>  }
> 
> base-commit: ffb217a13a2eaf6d5bd974fc83036a53ca69f1e2
> -- 
> https://chromeos.dev
>