uma for acpi object cache

[Jung-uk Kim]

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On 2013-01-26 03:30:27 -0500, Andriy Gapon wrote:
> on 25/01/2013 10:38 Andriy Gapon said the following:
>> on 24/01/2013 22:33 Jung-uk Kim said the following:
>>> On 2013-01-24 13:49:07 -0500, Andriy Gapon wrote:
>>>> on 24/01/2013 20:29 Jung-uk Kim said the following:
>>>>> When utcache.c works, it works fairly well, actually. :-)
>>> 
>>>> Well, my primary motivation for the patch is all the reports
>>>> about mysterious panics that seem to involve the cache: 
>>>> http://thread.gmane.org/gmane.os.freebsd.devel.acpi/7562 
>>>> http://thread.gmane.org/gmane.os.freebsd.devel.acpi/7613 
>>>> http://thread.gmane.org/gmane.os.freebsd.devel.acpi/7077
>>> 
>>>> There were a few more reports with the same theme. I hoped
>>>> that using uma(9) instead of hand-rolled code would lead to
>>>> better diagnostic and debugging cabilities.
>>> 
>>> Hmm...  I am not really sure local cache is to blame here.  If
>>> you really want to prove your theory, I think a simple
>>> modification to utcache.c should do:
>>> 
>>> Cache->LinkOffset = 8; Cache->ListName   = CacheName; 
>>> Cache->ObjectSize = ObjectSize; -    Cache->MaxDepth   =
>>> MaxDepth; +    Cache->MaxDepth   = 0;
>>> 
>>> *ReturnCache = Cache; return (AE_OK);
>>> 
>>> This should effectively kill object caching.
>> 
>> That's a very simple trick, I wonder why I didn't think about it
>> :-) Now I need to wait until one of the reporters resurfaces.
> 
> And just to clarify - I didn't and don't suspect the cache code
> itself. I suspect some code that uses the cache (directly or
> indirectly) - something like double-free or use-after-free, etc.

I haven't tried it for ages but ACPI_DBG_TRACK_ALLOCATIONS was meant
to track such problems.  Try adding it in acfreebsd.h.

Jung-uk Kim
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