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SubjectRe: [RFC PATCH 05/21] list: Comment missing WRITE_ONCE() in __list_del()
On Tue, Mar 24, 2020 at 03:36:27PM +0000, Will Deacon wrote:
> Although __list_del() is called from the RCU list implementation, it
> omits WRITE_ONCE() when updating the 'prev' pointer for the 'next' node.
> This is reasonable because concurrent RCU readers only access the 'next'
> pointers.
>
> Although it's obvious after reading the code, add a comment.
>
> Cc: Paul E. McKenney <paulmck@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Will Deacon <will@kernel.org>

OK, I will take the easy one. ;-)

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>

> ---
> include/linux/list.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/list.h b/include/linux/list.h
> index 4d9f5f9ed1a8..ec1f780d1449 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -109,6 +109,7 @@ static inline void list_add_tail(struct list_head *new, struct list_head *head)
> */
> static inline void __list_del(struct list_head * prev, struct list_head * next)
> {
> + /* RCU readers don't read the 'prev' pointer */
> next->prev = prev;
> WRITE_ONCE(prev->next, next);
> }
> --
> 2.20.1
>

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