linux-kernel - Re: [PATCH] freezer: use smp barriers

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Message-Id: <201104251238.36005.rjw@sisk.pl>
Date:	Mon, 25 Apr 2011 12:38:35 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mike Frysinger <vapier@...too.org>
Cc:	Pavel Machek <pavel@....cz>, linux-kernel@...r.kernel.org,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] freezer: use smp barriers

On Monday, April 25, 2011, Mike Frysinger wrote:
> The freezer processes are dealing with multiple threads running
> simultaneously, and on a UP system, the memory reads/writes do
> not need barriers to keep things in sync.  These are only needed
> on SMP systems, so use SMP barriers instead.
> 
> Signed-off-by: Mike Frysinger <vapier@...too.org>

Applied to suspend-2.6/linux-next.

Thanks,
Rafael


> ---
>  kernel/freezer.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/freezer.c b/kernel/freezer.c
> index 66ecd2e..7b01de9 100644
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -17,7 +17,7 @@ static inline void frozen_process(void)
>  {
>  	if (!unlikely(current->flags & PF_NOFREEZE)) {
>  		current->flags |= PF_FROZEN;
> -		wmb();
> +		smp_wmb();
>  	}
>  	clear_freeze_flag(current);
>  }
> @@ -93,7 +93,7 @@ bool freeze_task(struct task_struct *p, bool sig_only)
>  	 * the task as frozen and next clears its TIF_FREEZE.
>  	 */
>  	if (!freezing(p)) {
> -		rmb();
> +		smp_rmb();
>  		if (frozen(p))
>  			return false;
>  
> 

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