Re: [PATCH v7 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock

[Peter Zijlstra]

On Tue, Jan 21, 2020 at 09:29:19PM +0100, Peter Zijlstra wrote:
> @@ -92,8 +92,8 @@ static int __init cna_init_nodes(void)
>  }
>  early_initcall(cna_init_nodes);
>  
> -static inline bool cna_try_change_tail(struct qspinlock *lock, u32 val,
> -				       struct mcs_spinlock *node)
> +static inline bool cna_try_clear_tail(struct qspinlock *lock, u32 val,
> +				      struct mcs_spinlock *node)
>  {
>  	struct mcs_spinlock *head_2nd, *tail_2nd;
>  	u32 new;

Also, that whole function is placed wrong; it should be between
cna_wait_head_or_lock() and cna_pass_lock(), then it's in the order they
appear in the slow path, ie. the order they actually run.