Date: Tue, 31 May 2011 16:11:22 -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: <20110531221122.GA58836@nargothrond.kdm.org> In-Reply-To: <BANLkTinThaAeP9cAVpoGxpSNq2zn%2Ba-P6Q@mail.gmail.com> References: <201105311729.p4VHTwrZ033296@svn.freebsd.org> <BANLkTim1AQQj1BfqHtYfPWrvaQBp41qDNw@mail.gmail.com> <20110531214618.GA57498@nargothrond.kdm.org> <BANLkTinThaAeP9cAVpoGxpSNq2zn%2Ba-P6Q@mail.gmail.com>
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--17pEHd4RhPHOinZp Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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. Also, does the debugger work now that it has booted successfully? Thanks, Ken -- Kenneth Merry ken@FreeBSD.ORG --17pEHd4RhPHOinZp Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="subr_msgbuf.c.20110531.txt" Index: subr_msgbuf.c =================================================================== --- subr_msgbuf.c (revision 222537) +++ subr_msgbuf.c (working copy) @@ -61,6 +61,7 @@ mbp->msg_magic = MSG_MAGIC; mbp->msg_lastpri = -1; mbp->msg_needsnl = 0; + bzero(&mbp->msg_lock, sizeof(mbp->msg_lock)); mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN); } @@ -95,6 +96,7 @@ mbp->msg_lastpri = -1; /* Assume that the old message buffer didn't end in a newline. */ mbp->msg_needsnl = 1; + bzero(&mbp->msg_lock, sizeof(mbp->msg_lock)); mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN); } --17pEHd4RhPHOinZp--
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