Re: [PATCH v2] rcu, kasan: Record work creation stack trace with interrupts enabled

[Paul E. McKenney]

On Sun, Dec 26, 2021 at 08:52:04AM +0800, Zqiang wrote:
> Recording the work creation stack trace for KASAN reports in
> call_rcu() is expensive, due to unwinding the stack, but also
> due to acquiring depot_lock inside stackdepot (which may be contended).
> Because calling kasan_record_aux_stack_noalloc() does not require
> interrupts to already be disabled, this may unnecessarily extend
> the time with interrupts disabled.
> 
> Therefore, move calling kasan_record_aux_stack() before the section
> with interrupts disabled.
> 
> Acked-by: Marco Elver <elver@xxxxxxxxxx>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>

Applied, thank you both!

							Thanx, Paul

> ---
>  v1->v2:
>  Make the submitted information clearer.
> 
>  kernel/rcu/tree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 9b58bae0527a..36bd3f9e57b3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3068,8 +3068,8 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
>  	}
>  	head->func = func;
>  	head->next = NULL;
> -	local_irq_save(flags);
>  	kasan_record_aux_stack_noalloc(head);
> +	local_irq_save(flags);
>  	rdp = this_cpu_ptr(&rcu_data);
>  
>  	/* Add the callback to our list. */
> -- 
> 2.25.1
>