linux-kernel - Re: [PATCH] rcu: Remove debug_object_active_state() from debug_rcu_head

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Message-ID: <20220513004955.GC1790663@paulmck-ThinkPad-P17-Gen-1>
Date:   Thu, 12 May 2022 17:49:55 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Zqiang <qiang1.zhang@...el.com>
Cc:     frederic@...nel.org, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: Remove debug_object_active_state() from
 debug_rcu_head_queue/unqueue()

On Tue, May 10, 2022 at 11:07:48AM +0800, Zqiang wrote:
> Currently, the double call_rcu() detected only need call
> debug_object_activate() to check whether the rcu head object is
> activated, the rcu head object usage state check is not necessary
> and when call rcu_test_debug_objects() the debug_object_active_state()
> will output same callstack as debug_object_activate(). so remove
> debug_object_active_state() to reduce the output of repeated callstack.
> 
> Signed-off-by: Zqiang <qiang1.zhang@...el.com>

Could you please post the output of the dmesg output of a failed
check with your change?

							Thanx, Paul

> ---
>  kernel/rcu/rcu.h | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index 15b96f990774..0604ecd16627 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -179,27 +179,16 @@ static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
>   */
>  
>  #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
> -# define STATE_RCU_HEAD_READY	0
> -# define STATE_RCU_HEAD_QUEUED	1
>  
>  extern const struct debug_obj_descr rcuhead_debug_descr;
>  
>  static inline int debug_rcu_head_queue(struct rcu_head *head)
>  {
> -	int r1;
> -
> -	r1 = debug_object_activate(head, &rcuhead_debug_descr);
> -	debug_object_active_state(head, &rcuhead_debug_descr,
> -				  STATE_RCU_HEAD_READY,
> -				  STATE_RCU_HEAD_QUEUED);
> -	return r1;
> +	return debug_object_activate(head, &rcuhead_debug_descr);
>  }
>  
>  static inline void debug_rcu_head_unqueue(struct rcu_head *head)
>  {
> -	debug_object_active_state(head, &rcuhead_debug_descr,
> -				  STATE_RCU_HEAD_QUEUED,
> -				  STATE_RCU_HEAD_READY);
>  	debug_object_deactivate(head, &rcuhead_debug_descr);
>  }
>  #else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> -- 
> 2.25.1
>