linux-kernel - Re: [PATCH 2/2] x86, MCE: Cleanup macro __get_cpu

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Date:	Mon, 14 Apr 2014 09:20:08 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Chen, Gong" <gong.chen@...ux.intel.com>, tony.luck@...el.com
CC:	tglx@...utronix.de, mingo@...nel.org, linux-kernel@...r.kernel.org,
	linux-tip-commits@...r.kernel.org
Subject: Re: [PATCH 2/2] x86, MCE: Cleanup macro __get_cpu_var

On 04/14/2014 01:39 AM, Chen, Gong wrote:
> @@ -1287,14 +1287,14 @@ static unsigned long (*mce_adjust_timer)(unsigned long interval) =
>  
>  static int cmc_error_seen(void)
>  {
> -	unsigned long *v = &__get_cpu_var(mce_polled_error);
> +	unsigned long *v = this_cpu_ptr(&mce_polled_error);
>  
> -	return test_and_clear_bit(0, v);
> +	return this_cpu_xchg(*v, 0);
>  }
>  

Here you produce a pointer and *then* passing it through a this_cpu_
function... this is actively wrong.

It should simply be:

	return this_cpu_xchg(mce_polled_error, 0);

	-hpa

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