Date: Sat, 20 Aug 2011 13:02:25 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Steven Hartland <killing@multiplay.co.uk> Cc: freebsd-jail@FreeBSD.org, freebsd-stable@FreeBSD.org Subject: Re: debugging frequent kernel panics on 8.2-RELEASE Message-ID: <4E4F8631.1070300@FreeBSD.org> In-Reply-To: <4019027648B5493AAC4B654BD821DE88@multiplay.co.uk> References: <47F0D04ADF034695BC8B0AC166553371@multiplay.co.uk><A71C3ACF01EC4D36871E49805C1A5321@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>
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on 18/08/2011 02:15 Steven Hartland said the following: > In a nutshell the jail manager we're using will attempt to resurrect the jail > from a dieing state in a few specific scenarios. > > Here's an exmaple:- > 1. jail restart requested > 2. jail is stopped, so the java processes is killed off, but active tcp sessions > may prevent the timely full shutdown of the jail. > 3. if an existing jail is detected, i.e. a dieing jail from #2, instead of > starting a new jail we attach to the old one and exec the new java process. > 4. if an existing jail isnt detected, i.e. where there where not hanging tcp > sessions and #2 cleanly shutdown the jail, a new jail is created, attached to > and the java exec'ed. > > The system uses static jailid's so its possible to determine if an existing > jail for this "service" exists or not. This prevents duplicate services as > well as making services easy to identify by their jailid. > > So what we could be seeing is a race between the jail shutdown and the attach > of the new process? Not a jail expert at all, but a few suggestions... First, wouldn't the 'persist' jail option simplify your life a little bit? Second, you may want to try to monitor value of prison0.pr_uref variable (e.g. via kgdb) while executing various scenarios of what you do now. If after finishing a certain scenario you end up with a value lower than at the start of scenario, then this is the troublesome one. Please note that prison0.pr_uref is composed from a number of non-jailed processes plus a number of top-level jails. So take this into account when comparing prison0.pr_uref values - it's better to record the initial value when no jails are started and it's important to keep the number of non-jailed processes the same (or to account for its changes). -- Andriy Gapon
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