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Date:      Tue, 31 May 2011 16:40:55 -0600
From:      "Kenneth D. Merry" <ken@FreeBSD.org>
To:        mdf@FreeBSD.org
Cc:        svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org
Subject:   Re: svn commit: r222537 - in head/sys: kern sys
Message-ID:  <20110531224055.GA59252@nargothrond.kdm.org>
In-Reply-To: <BANLkTimh=ND77iP95dTR0ZaXJJCBFATQuQ@mail.gmail.com>
References:  <201105311729.p4VHTwrZ033296@svn.freebsd.org> <BANLkTim1AQQj1BfqHtYfPWrvaQBp41qDNw@mail.gmail.com> <20110531214618.GA57498@nargothrond.kdm.org> <BANLkTinThaAeP9cAVpoGxpSNq2zn%2Ba-P6Q@mail.gmail.com> <20110531221122.GA58836@nargothrond.kdm.org> <BANLkTimh=ND77iP95dTR0ZaXJJCBFATQuQ@mail.gmail.com>

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On Tue, May 31, 2011 at 15:16:05 -0700, mdf@FreeBSD.org wrote:
> On Tue, May 31, 2011 at 3:11 PM, Kenneth D. Merry <ken@freebsd.org> wrote:
> > On Tue, May 31, 2011 at 15:02:37 -0700, mdf@FreeBSD.org wrote:
> >> On Tue, May 31, 2011 at 2:46 PM, Kenneth D. Merry <ken@freebsd.org> wrote:
> >> > On Tue, May 31, 2011 at 14:00:18 -0700, mdf@FreeBSD.org wrote:
> >> >> On Tue, May 31, 2011 at 10:29 AM, Kenneth D. Merry <ken@freebsd.org> wrote:
> >> >> > Author: ken
> >> >> > Date: Tue May 31 17:29:58 2011
> >> >> > New Revision: 222537
> >> >> > URL: http://svn.freebsd.org/changeset/base/222537
> >> >> >
> >> >> > Log:
> >> >> > ?Fix apparent garbage in the message buffer.
> >> >> >
> >> >> > ?While we have had a fix in place (options PRINTF_BUFR_SIZE=128) to fix
> >> >> > ?scrambled console output, the message buffer and syslog were still getting
> >> >> > ?log messages one character at a time. ?While all of the characters still
> >> >> > ?made it into the log (courtesy of atomic operations), they were often
> >> >> > ?interleaved when there were multiple threads writing to the buffer at the
> >> >> > ?same time.
> >> >>
> >> >> This seems to panic my box with "lock "msgbuf" 0xfffffe0127ffffe0
> >> >> already initialized".
> >> >>
> >> >> Unfortunately, though I booted with a fresh CURRENT this morning
> >> >> successfully, both /boot/kernel and /boot/kernel.old give this panic.
> >> >> To add insult to injury, when the kernel drops into the debugger, my
> >> >> keyboard input no longer works so I can't get a stack, etc.
> >> >
> >> > Uh-oh!
> >> >
> >> >> So:
> >> >>
> >> >> 1) Is there anything else I can do to help debug this?
> >> >> 2) how can I resurrect this box without a reinstall?
> >> >>
> >> >> I will try to repro on a virtual machine so I have a snapshot to come back to.
> >> >
> >> > My guess is that this is an issue with the message buffer reinitialization
> >> > path. ?lock_init() (called by mtx_init()) has an assert to make sure that
> >> > the lock is initialized, and that is just a flag check.
> >> >
> >> > Since the spin lock is part of the message buffer structure, if it is held
> >> > over from a previous boot, the LO_INITIALIZED flag may still be set.
> >> >
> >> > Try power cycling the machine. ?If it is an issue with re-initialization,
> >> > that should clear the memory and allow you to boot.
> >>
> >> Hmm, apparently my previous presses of the power button weren't long
> >> enough. ?I let it sit off for 20 seconds and it boots okay now.
> >
> > Okay, so it probably is the re-initialization code. ?Can you try this patch
> > and see if it survives a warm boot? ?I also changed the initialization
> > path, so we don't get tripped up by garbage left in memory.
> 
> This patch survived a warm reboot (shutdown -r now).

Cool!  I just checked in the patch.

> > Also, does the debugger work now that it has booted successfully?
> 
> The debugger (or rather, my keyboard in the debugger) works on a
> successful boot.  I used sysctl debug.kdb.enter=1 to test it.

Ahh, glad things are working there too.

Let me know if you (or anyone else) run into any more issues.

Thanks for testing this!

Ken
-- 
Kenneth Merry
ken@FreeBSD.ORG



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