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Date:      Mon, 22 Oct 2007 16:29:32 +0400
From:      "Oleg Derevenetz" <oleg@vsi.ru>
To:        "Alfred Perlstein" <alfred@freebsd.org>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: kern/104406: [ufs] Processes get stuck in "ufs" stateunderpersistent CPU load
Message-ID:  <027d01c814a7$35e408d0$c8c55358@delloleg>
References:  <027d01c8125c$73d4db80$c8c55358@delloleg><20071019220501.GL31826@elvis.mu.org><006d01c8133a$674a90b0$eec55358@W2KOOOD> <20071020192601.GW31826@elvis.mu.org>

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>> > > Can anyone take a look on PR kern/104406 ? I got repeatable hang
>> situation,
>> > > but I can't obtain a kernel dump to get result of all show commands from
>> > > here:
>> > >
>> > >
>> http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html
>> > >
>> > > After my break to debugger using Ctrl+Alt+Esc sequence and entering a
>> > > "panic" command kernel does not wrote a kernel dump but seems to hang.
>> Can
>> > > anyone describe how to obtain a kernel dump in this situation, or at
>> least
>> > > say - which output of show commands need in first place to debug this ?
>> > > Output of all suggested commands is huge and I afraid of making mistake
>> > > when carrying this output from screen to list of paper and back :-)
>> >
>> > Oleg, one thing you can do to make this less painful is to
>> > run your machine's console over serial port.
>> >
>> > First get a crossover serial cable, make sure it works from one
>> > box to another, it should be easy to run "tip com1" on both
>> > boxes to ensure that it works.
>> >
>> > Then you just need to add console=comconsole to /boot/loader.conf
>> > and your box's console should come over serial.
>> >
>> > Then on the machine watching the console, you can just do this:
>> >
>> > % script
>> > Script started, output file is typescript
>> > % tip com1
>> > ...do ddb stuff now...
>> > ...stop tip
>> > % exit
>> >
>> > now you should have everything logged into a file called "typescript"
>> > should save you a big headache.
>>
>> Thanks, I'll try it in the monday morning.

I posted a followup to kern/104406 that includes all information listed in "Debugging Deadlocks" chapter of FreeBSD Developer's 
Handbook. Can anyone take a look on it and say - is this certainly a hardware problem or some sort of software problem ?

--
Oleg Derevenetz <oleg@vsi.ru> OOD3-RIPE
Phone: +7 4732 539880
Fax:   +7 4732 531415         http://www.vsi.ru
CenterTelecom Voronezh ISP    http://isp.vsi.ru




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