Re: [PATCH 3/3] rcu: Report callbacks enqueued on offline CPU blind spot

[Frederic Weisbecker <frederic@kernel.org>]

Le Wed, Oct 02, 2024 at 04:57:38PM +0200, Frederic Weisbecker a écrit :
> Callbacks enqueued after rcutree_report_cpu_dead() fall into RCU barrier
> blind spot. Report any potential misuse.
> 
> Reported-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> ---
>  kernel/rcu/tree.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index a60616e69b66..36070b6bf4a1 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3084,8 +3084,11 @@ __call_rcu_common(struct rcu_head *head, rcu_callback_t func, bool lazy_in)
>  	head->func = func;
>  	head->next = NULL;
>  	kasan_record_aux_stack_noalloc(head);
> +
>  	local_irq_save(flags);
>  	rdp = this_cpu_ptr(&rcu_data);
> +	RCU_LOCKDEP_WARN(rcu_rdp_cpu_online(rdp), "Callback enqueued on offline
> CPU!");

This should be !rcu_rdp_cpu_online(rdp)

Sigh...

> +
>  	lazy = lazy_in && !rcu_async_should_hurry();
>  
>  	/* Add the callback to our list. */
> -- 
> 2.46.0
> 
>