Re: applesmc oops in 3.10/3.11

From: Guenter Roeck
Date: Thu Sep 26 2013 - 06:53:27 EST

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.



From dedefba9167913c46e1896ce0624e68ffe95d532 Mon Sep 17 00:00:00 2001
From: Henrik Rydberg <rydberg@xxxxxxxxxxx>
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

Reported-by: <jwboyer@xxxxxxxxxxxxxxxxx>
Suggested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
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 ?


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