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Date:      Sat, 20 Oct 2007 20:58:08 +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" state underpersistent CPU load
Message-ID:  <006d01c8133a$674a90b0$eec55358@W2KOOOD>
References:  <027d01c8125c$73d4db80$c8c55358@delloleg> <20071019220501.GL31826@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.

> As far as getting a dump from ddb, try this:
>
> ddb> call doadump
>
> I'm completely at a loss why this isn't a base ddb command "dump"
> but whatever... :)

Unfortunately, this doesn't work too. I called duty personnel in this
datacenter and asked them to do this, and person on duty tells me that after
he enters this command something like that arrives on monitor:

db> call doadump
Dumping 3072 MB

Dump aborted error I/O
Dump failed. (Error 5)

--
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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