Subject: Re: linux-next: manual merge of the rcu tree with the mm tree

From: Stephen Rothwell <[email-masked]>
Date: Wed, 22 Jan 2025 14:13:11 +1100

Hi all,

On Fri, 20 Dec 2024 13:37:38 +1100 Stephen Rothwell <[email-masked]> wrote:
>
> Today's linux-next merge of the rcu tree got a conflict in:
> 
>   kernel/rcu/tree.c
> 
> between commit:
> 
>   bf8f464ee259 ("kasan: make kasan_record_aux_stack_noalloc() the default behaviour")
> 
> from the mm tree and commit:
> 
>   049dfe96baf9 ("rcu: Report callbacks enqueued on offline CPU blind spot")
> 
> from the rcu tree.
> 
> I fixed it up (see below) and can carry the fix as necessary. This
> is now fixed as far as linux-next is concerned, but any non trivial
> conflicts should be mentioned to your upstream maintainer when your tree
> is submitted for merging.  You may also want to consider cooperating
> with the maintainer of the conflicting tree to minimise any particularly
> complex conflicts.
> 
> -- 
> Cheers,
> Stephen Rothwell
> 
> diff --cc kernel/rcu/tree.c
> index 3885aae5f9cb,24f1cb292a92..000000000000
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@@ -3083,9 -3083,12 +3083,12 @@@ __call_rcu_common(struct rcu_head *head
>   	}
>   	head->func = func;
>   	head->next = NULL;
>  -	kasan_record_aux_stack_noalloc(head);
>  +	kasan_record_aux_stack(head);
> + 
>   	local_irq_save(flags);
>   	rdp = this_cpu_ptr(&rcu_data);
> + 	RCU_LOCKDEP_WARN(!rcu_rdp_cpu_online(rdp), "Callback enqueued on offline CPU!");
> + 
>   	lazy = lazy_in && !rcu_async_should_hurry();
>   
>   	/* Add the callback to our list. */

This is now a conflict between the mm-stable tree and Linus' tree.

-- 
Cheers,
Stephen Rothwell