From owner-freebsd-smp  Mon Oct  2 16:42: 3 2000
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Date: Mon, 2 Oct 2000 16:41:39 -0700
From: Jason Evans <jasone@canonware.com>
To: Steve Kargl <sgk@troutmask.apl.washington.edu>
Cc: freebsd-smp@freebsd.org
Subject: Re: witness code status?
Message-ID: <20001002164139.I58256@canonware.com>
References: <200010022332.e92NWan00373@troutmask.apl.washington.edu>
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In-Reply-To: <200010022332.e92NWan00373@troutmask.apl.washington.edu>; from sgk@troutmask.apl.washington.edu on Mon, Oct 02, 2000 at 04:32:36PM -0700
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On Mon, Oct 02, 2000 at 04:32:36PM -0700, Steve Kargl wrote:
> What's the current status of the integration of BSDi's
> witness code?  If I include "options WITNESS" in my kernel
> config file, I get an immediate panic at boot.  My sources
> are from today (01 Oct 00), and the system is currently
> running a MP kernel (built without the witness code).
> 
> PS:  Yes, I know there will be periods of instability, but 
>      you (the SMP developers) can't possibly have all combinations
>      of MP hardware.

I (and others) have been running kernels with the witness code enabled for
over a month.  The witness code's purpose is to detect lock cycles that
could cause deadlock, among other incorrect mutex uses.  The stack trace
and panic message in your email seem indicate a programming error.  In
other words, the witness code is doing its job.

Jason

> panic: mutex_enter: MTX_DEF on MTX_SPIN mutex random harvest\
> @/usr/src/sys/modules/randomdev/../../dev/randomdev/yarrow.c:515
> cpuid = 1; lapic.id = 00000000
> Debugger("panic')
> 
> CPU1 stopping CPUs: 0x00000001 stopped
> Stopped at Debugger+0x38:  movb $0,in_Debugger.684
> 
> db>trace
> Debugger(c0277da1)
> panic
> witness_enter
> _mtx_enter
> random_harvest_internal
> write_random
> random_write
> ufs_vnoperatespec
> vn_write
> dofilewrite
> write
> syscall2
> Xint0x80_syscall


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