linux-kernel - Re: [PATCH 3/4]percpu_counter: fix code for 32bit systems

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Message-ID: <20110412190251.GD16342@mtj.dyndns.org>
Date:	Wed, 13 Apr 2011 04:02:51 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, cl@...ux.com
Subject: Re: [PATCH 3/4]percpu_counter: fix code for 32bit systems

On Tue, Apr 12, 2011 at 04:04:04PM +0800, Shaohua Li wrote:
>  static inline s64 percpu_counter_read(struct percpu_counter *fbc)
>  {
> +#if BITS_PER_LONG == 32
> +	s64 count;
> +	spin_lock(&fbc->lock);
> +	count = fbc->count;
> +	spin_unlock(&fbc->lock);
> +	return count;
> +#else
>  	return fbc->count;
> +#endif

I don't know.  Is there any problem caused by this?  The interface is
known to be unreliable and already being used in speculative manner.
I think it's more beneficial to avoid using locks on fast read path.

Thanks.

-- 
tejun
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