Date: Sat, 20 Aug 2011 16:51:50 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Andriy Gapon" <avg@FreeBSD.org> Cc: freebsd-jail@FreeBSD.org, freebsd-stable@FreeBSD.org Subject: Re: debugging frequent kernel panics on 8.2-RELEASE Message-ID: <82E865FBA30747078AF6EE3C1701F973@multiplay.co.uk> References: <47F0D04ADF034695BC8B0AC166553371@multiplay.co.uk><4E4380C0.7070908@FreeBSD.org><EBC06A239BAB4B3293C28D793329F9CA@multiplay.co.uk><4E43E272.1060204@FreeBSD.org><62BF25D0ED914876BEE75E2ADF28DDF7@multiplay.co.uk><4E440865.1040500@FreeBSD.org><6F08A8DE780545ADB9FA93B0A8AA4DA1@multiplay.co.uk><4E441314.6060606@FreeBSD.org><2C4B0D05C8924F24A73B56EA652FA4B0@multiplay.co.uk><4E48D967.9060804@FreeBSD.org><9D034F992B064E8092E5D1D249B3E959@multiplay.co.uk><4E490DAF.1080009@FreeBSD.org><796FD5A096DE4558B57338A8FA1E125B@multiplay.co.uk><4E491D01.1090902@FreeBSD.org><570C5495A5E242F7946E806CA7AC5D68@multiplay.co.uk><4E4AD35C.7020504@FreeBSD.org><6A7238AED44542A880B082A40304D940@multiplay.co.uk><4E4BA21F.6010805@FreeBSD.org><581C95046B0948FC82D6F2E86948F87B@multiplay.co.uk><4E4BBA7F.30907@FreeBSD.org><88A6CE3E8B174E0694A3A9A5283479B4@multiplay.co.uk><4E4C22D6.6070407@FreeBSD.org><4019027648B5493AAC4B654BD821DE88@multiplay.co.uk><4E4F8631.1070300@FreeBSD.org> <4E4F8821.80108@Fre eBSD.org>
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----- Original Message -----
From: "Andriy Gapon" <avg@FreeBSD.org>
> BTW, I suspect the following scenario, but I am not able to verify it either via
> testing or in the code:
> - last process in a dying jail exits
> - pr_uref of the jail reaches zero
> - pr_uref of prison0 gets decremented
> - you attach to the jail and resurrect it
> - but pr_uref of prison0 stays decremented
>
> Repeat this enough times and prison0.pr_uref reaches zero.
> To reach zero even sooner just kill enough of non-jailed processes.
I've just checked across a number of the panic dumps from the
past few days and they all have prison0.pr_uref = 0 which confirms
the cause of the panic.
I've tried scripting continuous jail start stops, but even after 1000's
of iterations have been unable to trigger this on my test machine, so
I'm going to dig into the jail code to see if I can find out how its
incorrectly decrementing prison0 via inspection.
Regards
Steve
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