linux-kernel - Re: applesmc oops in 3.10/3.11

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Message-ID: <5244121B.7070904@roeck-us.net>
Date:	Thu, 26 Sep 2013 03:53:15 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Henrik Rydberg <rydberg@...omail.se>
CC:	Josh Boyer <jwboyer@...oraproject.org>, khali@...ux-fr.org,
	lm-sensors@...sensors.org,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	bugzilla@...orremedies.com
Subject: Re: applesmc oops in 3.10/3.11

On 09/25/2013 11:34 PM, Henrik Rydberg wrote:
>>>> This suggests that initialization may be attempted more than once. The key cache
>>>> is allocated only once, but the number of keys is read for each attempt.
>>>>
>>>> No idea if that can happen, but if the number of keys can increase after
>>>> the first initialization attempt you would have an explanation for the crash.
>>>
>>> Good idea, and easy enough to test with the patch below.
>>>
>> Should we apply this patch even though it may not solve the specific problem ?
>
> Yes, why not - it certainly won't hurt. I am running it right now, so
> it is at least run-tested.
>
>> Again, not sure if the key count can change, but the current code is at the very
>> least inconsistent, as it keeps reading the key count without updating or
>> verifying the cache size.
>
> Yes - I agree that the error state is far-fetched, but it is hard to
> see any other logical explanation. There is of course always the
> possibility that the problem is somewhere else completely.
>
> Proper patch attached.
>
> Thanks,
> Henrik
>
> ---
>
>>>From dedefba9167913c46e1896ce0624e68ffe95d532 Mon Sep 17 00:00:00 2001
> From: Henrik Rydberg <rydberg@...omail.se>
> Date: Thu, 26 Sep 2013 08:33:16 +0200
> Subject: [PATCH] hwmon: (applesmc) Check key count before proceeding
>
> After reports from Chris and Josh Boyer of a rare crash in applesmc,
> Guenter pointed at the initialization problem fixed below. The patch
> has not been verified to fix the crash, but should be applied
> regardless.
>
> Reported-by: <jwboyer@...oraproject.org>
> Suggested-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Henrik Rydberg <rydberg@...omail.se>
> ---
>   drivers/hwmon/applesmc.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)

Applied. I'll run my sanity tests before I send it upstream.
I'll also Cc: stable.

Interesting is that this started to happen with 3.10, even though
I did not find any relevant changes in the driver. Is it possible that
changed boot timing (ie reduced boot time) exposes this problem ?

Thanks,
Guenter

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