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Date:      Tue, 27 Feb 2007 09:05:53 +0000 (GMT)
From:      Robert Watson <rwatson@FreeBSD.org>
To:        Jiawei Ye <leafy7382@gmail.com>
Cc:        freebsd-current <freebsd-current@freebsd.org>
Subject:   Re: Processes stuck in *unp_m after recent uipc changes
Message-ID:  <20070227090505.K56223@fledge.watson.org>
In-Reply-To: <20070227084214.Y56223@fledge.watson.org>
References:  <c21e92e20702270007u277d6a9xfaca7883da9dedd@mail.gmail.com> <20070227084214.Y56223@fledge.watson.org>

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On Tue, 27 Feb 2007, Robert Watson wrote:

> On Tue, 27 Feb 2007, Jiawei Ye wrote:
>
>> With the latest uipc locking changes, I experienced a hard lockup on my 
>> -current machine. Many processes got stuck in *unp_m state and 
>> ctrl-alt-delete at the console cannot properly restart the machine and I 
>> had to hard-reset (no coredump available). Is there anyway to diagnose 
>> this?
>
> Please configure WITNESS, DDB, and BREAK_TO_DEBUGGER on a box with a serial 
> console.  Then attach the output of "ps", "show alllocks", and "alltrace" to 
> an e-mail.  With any luck, this is a leaked lock in some missed error case 
> and we can just add a missing unlock.  Thanks!

Obviously, INVARIANTS also good on general principle. :-)

See the handbook chapter on debugging, and in particular live DDB debugging, 
if you're running into any problems.

Robert N M Watson
Computer Laboratory
University of Cambridge



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