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

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Message-ID: <52440E15.7060002@roeck-us.net>
Date:	Thu, 26 Sep 2013 03:36:05 -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.
>
There are also ACPI conflicts in each of the bug reports I looked at.
Can this play a role, or is that "normal" on apple systems ?

Thanks,
Guenter

> 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(-)
>
> diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
> index 62c2e32..98814d1 100644
> --- a/drivers/hwmon/applesmc.c
> +++ b/drivers/hwmon/applesmc.c
> @@ -525,16 +525,25 @@ static int applesmc_init_smcreg_try(void)
>   {
>   	struct applesmc_registers *s = &smcreg;
>   	bool left_light_sensor, right_light_sensor;
> +	unsigned int count;
>   	u8 tmp[1];
>   	int ret;
>
>   	if (s->init_complete)
>   		return 0;
>
> -	ret = read_register_count(&s->key_count);
> +	ret = read_register_count(&count);
>   	if (ret)
>   		return ret;
>
> +	if (s->cache && s->key_count != count) {
> +		pr_warn("key count changed from %d to %d\n",
> +			s->key_count, count);
> +		kfree(s->cache);
> +		s->cache = NULL;
> +	}
> +	s->key_count = count;
> +
>   	if (!s->cache)
>   		s->cache = kcalloc(s->key_count, sizeof(*s->cache), GFP_KERNEL);
>   	if (!s->cache)
>

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