Subject: Re: [PATCH resent] Documentation: rw_lock lessons learned

From: "Paul E. McKenney" <[email-masked]>
Date: Tue, 10 Nov 2009 13:22:43 -0800

On Tue, Nov 10, 2009 at 02:55:44PM -0500, William Allen Simpson wrote:
> In recent weeks, two different network projects erroneously
> strayed down the rw_lock path.  Update the Documentation
> based upon comments in those threads.
>
> Signed-off-by: [email-masked]
> ---
>   Documentation/spinlocks.txt |   14 ++++++++++++++
>   1 files changed, 14 insertions(+), 0 deletions(-)
>

> diff --git a/Documentation/spinlocks.txt b/Documentation/spinlocks.txt
> index 619699d..c112052 100644
> --- a/Documentation/spinlocks.txt
> +++ b/Documentation/spinlocks.txt
> @@ -233,4 +233,18 @@ indeed), while write-locks need to protect themselves against interrupts.
> 
>  		Linus

As you might guess, works for me!!!

Acked-by: Paul E. McKenney <[email-masked]>

> +----
> +
> +The implications of spin_locks on memory are further described in:
> +
> +  Documentation/memory-barriers.txt
> +    (5) LOCK operations.
> +    (6) UNLOCK operations.
> +
> +----
> +
> +We are working hard to remove reader-writer spinlocks (rw_lock) from the
> +network stack, so please don't add a new one.  Instead, see:
> +
> +  Documentation/RCU/rcu.txt
> 
> -- 
> 1.6.3.3
> 
>