linux-kernel - Re: [PATCH next] rcu: stop spurious warnings from synchronize_sched

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Message-ID: <20120217221005.GX2976@linux.vnet.ibm.com>
Date:	Fri, 17 Feb 2012 14:10:05 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] rcu: stop spurious warnings from
 synchronize_sched_expedited

On Fri, Feb 17, 2012 at 01:20:31PM -0800, Hugh Dickins wrote:
> synchronize_sched_expedited() is spamming CONFIG_DEBUG_PREEMPT=y
> users with an unintended warning from the cpu_is_offline() check:
> use raw_smp_processor_id() instead of smp_processor_id() there.

Good catch!  Queued.

						Thanx, Paul

> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> ---
> 
>  kernel/rcutree.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- next/kernel/rcutree.c	2012-02-17 08:02:15.680065066 -0800
> +++ linux/kernel/rcutree.c	2012-02-17 10:41:18.764003566 -0800
> @@ -2014,7 +2014,7 @@ void synchronize_sched_expedited(void)
>  	/* Note that atomic_inc_return() implies full memory barrier. */
>  	firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
>  	get_online_cpus();
> -	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
> +	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
> 
>  	/*
>  	 * Each pass through the following loop attempts to force a
> 

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