Date: Wed, 16 Nov 2011 14:14:46 +0000 (UTC) From: "Bjoern A. Zeeb" <bz@FreeBSD.org> To: Alexander Motin <mav@FreeBSD.org> Cc: freebsd-stable@freebsd.org Subject: Re: ATA/Cdrom(?) panic Message-ID: <alpine.BSF.2.00.1111161414150.4603@ai.fobar.qr> In-Reply-To: <4EC392DA.2030302@FreeBSD.org> References: <alpine.BSF.2.00.1111160640370.4603@ai.fobar.qr> <4EC392DA.2030302@FreeBSD.org>
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On Wed, 16 Nov 2011, Alexander Motin wrote:
> Hi.
>
> On 11/16/11 08:43, Bjoern A. Zeeb wrote:
>> we have seen this or a very similar panic for about 1 year now once in
>> a while and I think I reported it before; this is FreeBSD as guest on
>> vmware. Seems it was a double panic this time. Could someone please
>> see what's going on there? It was on 8.x-STABLE in the past and this
>> is 8.2-RELEASE-p4.
>
> The part of code reporting "completing request directly" is IMHO broken
> by design. It returns request completion before request will actually be
> completed by lower levels without any knowledge of what's going on
> there. There is kind of protection against double request completion,
> but it looks like not always working. May be because that part of code
> is not locked and nothing prevents that semaphore timeout and normal
> request timeout/completion to happen simultaneously. It is surprising to
> see even two traps same time, not sure what synchronized them so precisely.
>
> Simple removing that semaphore timeout is not an option, because it will
> cause deadlock when this wait happen within taskqueue thread that is
> used to handle requests completion and abort that wait. Avoid waiting
> inside taskqueue is also impossible without major rewrite. That's why
> ATA_CAM drops that code completely.
So the bottom line of what you are saying is:
1) it's hard to fix right in 8
2) it's not an issue in 9 anymore at all?
--
Bjoern A. Zeeb You have to have visions!
Stop bit received. Insert coin for new address family.
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