Date: Sat, 26 Jan 2013 10:30:27 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Jung-uk Kim <jkim@FreeBSD.org> Cc: freebsd-acpi@FreeBSD.org Subject: Re: uma for acpi object cache Message-ID: <51039423.2070203@FreeBSD.org> In-Reply-To: <51024475.20909@FreeBSD.org> References: <20130122175629.GA1714@garage.freebsd.pl> <51008661.4060006@FreeBSD.org> <510101B4.4030409@FreeBSD.org> <51017D79.6060202@FreeBSD.org> <51018223.4030702@FreeBSD.org> <51019AAE.10501@FreeBSD.org> <51024475.20909@FreeBSD.org>
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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. -- Andriy Gapon
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