linux-kernel - Re: [RFC PATCH 08/21] Revert "list: Use WRITE_ONCE() when initializing list

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Message-ID: <20200330232505.GD19865@paulmck-ThinkPad-P72>
Date:   Mon, 30 Mar 2020 16:25:05 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Maddie Stone <maddiestone@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com,
        kernel-hardening@...ts.openwall.com
Subject: Re: [RFC PATCH 08/21] Revert "list: Use WRITE_ONCE() when
 initializing list_head structures"

On Tue, Mar 24, 2020 at 03:36:30PM +0000, Will Deacon wrote:
> This reverts commit 2f073848c3cc8aff2655ab7c46d8c0de90cf4e50.
> 
> There is no need to use WRITE_ONCE() to initialise a non-RCU 'list_head'.
> 
> Cc: Paul E. McKenney <paulmck@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Will Deacon <will@...nel.org>

And attention to lockless uses of list_empty() here, correct?

Depending on the outcome of discussions on 3/21, I should have added in
all three cases.

							Thanx, Paul

> ---
>  include/linux/list.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/list.h b/include/linux/list.h
> index c7331c259792..b86a3f9465d4 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -32,7 +32,7 @@
>   */
>  static inline void INIT_LIST_HEAD(struct list_head *list)
>  {
> -	WRITE_ONCE(list->next, list);
> +	list->next = list;
>  	list->prev = list;
>  }
>  
> -- 
> 2.20.1
>