linux-kernel - Re: [PATCH] hwmon: coretemp: fix oops on cpu unplug

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Message-ID: <20120501210041.GA10629@otc-wbsnb-06>
Date:	Wed, 2 May 2012 00:00:41 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Guenter Roeck <guenter.roeck@...csson.com>
Cc:	Fenghua Yu <fenghua.yu@...el.com>, Andi Kleen <ak@...ux.intel.com>,
	Jean Delvare <khali@...ux-fr.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] hwmon: coretemp: fix oops on cpu unplug

On Tue, May 01, 2012 at 08:20:14AM -0700, Guenter Roeck wrote:
> On Mon, Apr 30, 2012 at 09:18:01AM -0400, Kirill A. Shutemov wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> > 
> > coretemp tries to access core_data array beyond bounds on cpu unplug if
> > core id of the cpu if more than NUM_REAL_CORES-1.
> > 
> [ ... ]
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> 
> Looking at it again, you were right. Adding the check to get_core_online()
> doesn't really help as the platform device is per CPU, not per core.
> 
> Applied. I'll submit a separate patch to increase NUM_REAL_CORES.

Actually, the problem is bigger.

Documentation/cputopology.txt:
====
2) /sys/devices/system/cpu/cpuX/topology/core_id:

        the CPU core ID of cpuX. Typically it is the hardware platform's
        identifier (rather than the kernel's).  The actual value is
        architecture and platform dependent.
====

We should not use core id as an index in an array since it's an arbitrary
number (from kernel POV).

-- 
 Kirill A. Shutemov
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