linux-kernel - Re: [PATCH v7 2/2] mm: make lru_add_drain

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Message-ID: <20130813232904.GJ28996@mtj.dyndns.org>
Date:	Tue, 13 Aug 2013 19:29:04 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Chris Metcalf <cmetcalf@...era.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: Re: [PATCH v7 2/2] mm: make lru_add_drain_all() selective

Hello,

On Tue, Aug 13, 2013 at 06:53:32PM -0400, Chris Metcalf wrote:
>  int lru_add_drain_all(void)
>  {
> -	return schedule_on_each_cpu(lru_add_drain_per_cpu);
> +	return schedule_on_each_cpu_cond(lru_add_drain_per_cpu,
> +					 lru_add_drain_cond, NULL);

It won't nest and doing it simultaneously won't buy anything, right?
Wouldn't it be better to protect it with a mutex and define all
necessary resources statically (yeah, cpumask is pain in the ass and I
think we should un-deprecate cpumask_t for static use cases)?  Then,
there'd be no allocation to worry about on the path.

Thanks.

-- 
tejun
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