linux-kernel - Re: [PATCH -mm][v2] ratelimit rewrite

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Message-Id: <20080508122514.63482a06.akpm@linux-foundation.org>
Date:	Thu, 8 May 2008 12:25:14 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dave Young <hidave.darkstar@...il.com>
Cc:	paulmck@...ibm.com, joe@...ches.com, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm][v2] ratelimit rewrite

On Tue, 6 May 2008 10:25:58 +0800
Dave Young <hidave.darkstar@...il.com> wrote:

>  static inline void rcu_enter_nohz(void)
>  {
> +	static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
>  	smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
>  	__get_cpu_var(rcu_dyntick_sched).dynticks++;
> -	WARN_ON_SECS(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1, 10);
> +	WARN_ON_RATELIMIT(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1, &rs);
>  }
>  
>  static inline void rcu_exit_nohz(void)
>  {
> +	static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
>  	__get_cpu_var(rcu_dyntick_sched).dynticks++;
>  	smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
> -	WARN_ON_SECS(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1), 10);
> +	WARN_ON_RATELIMIT(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1),
> +			&rs);

Why are we altering the RCU code in this patch, btw?  It seems fairly
random that we happened to choose these particular WARN_ONs.  Do they have
a history of triggering?

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