linux-kernel - Re: [PATCH] x86: read apic id if it is not acpi

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Message-ID: <20090511092026.GA26444@elte.hu>
Date:	Mon, 11 May 2009 11:20:26 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ed Swierk <eswierk@...stanetworks.com>
Subject: Re: [PATCH] x86: read apic id if it is not acpi_lapic -v2


* Yinghai Lu <yinghai@...nel.org> wrote:

> +	new_apicid  = read_apic_id();
> +	if (boot_cpu_physical_apicid != new_apicid) {
> +		boot_cpu_physical_apicid  = new_apicid;
> +		apic_version[new_apicid] =
> +			 GET_APIC_VERSION(apic_read(APIC_LVR));
>  	}

_Please_, when we override something as critical as this and change 
the behavior of Linux (even if it's arguably a fix), we must printk 
a single line to the syslog so that people know what's going on.

You really need to make a conscious mental distinction between 
'dangerous' code and harmless changes, and apply a lot more 
conservative approach when you meet and touch (and introduce ...) 
dangerous code.

Thanks,

	Ingo
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