linux-kernel - Re: [tip:x86/urgent] x86, CMCI: Add proper detection of end of CMCI storms

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Message-ID: <53481FD5.9000405@zytor.com>
Date:	Fri, 11 Apr 2014 10:01:09 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	linux-kernel@...r.kernel.org, mingo@...nel.org, wdauchy@...il.com,
	tglx@...utronix.de, tony.luck@...el.com, gong.chen@...ux.intel.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/urgent] x86, CMCI: Add proper detection of end of CMCI
 storms

On 04/02/2014 12:55 AM, tip-bot for Chen, Gong wrote:
> @@ -614,6 +618,8 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
>  		if (!(m.status & MCI_STATUS_VAL))
>  			continue;
>  
> +		v = &get_cpu_var(mce_polled_error);
> +		set_bit(0, v);
>  		/*
>  		 * Uncorrected or signalled events are handled by the exception
>  		 * handler when it is enabled, so don't process those here.
> @@ -1278,10 +1284,18 @@ static unsigned long mce_adjust_timer_default(unsigned long interval)
>  static unsigned long (*mce_adjust_timer)(unsigned long interval) =
>  	mce_adjust_timer_default;
>  
> +static int cmc_error_seen(void)
> +{
> +	unsigned long *v = &__get_cpu_var(mce_polled_error);
> +
> +	return test_and_clear_bit(0, v);
> +}
> +

Please use this_cpu_*() whereever possible instead of __get_cpu_var().
Since this is not actually a bitmask this_cpu_xchg() can be used at the end.

In fact, using set_bit() is completely wasteful.

I'll push this onward since it is a bit late, but please submit a
cleanup patch.

	-hpa


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