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From: Robert Watson <rwatson@FreeBSD.org>
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To: Wilko Bulte <wb@freebie.xs4all.nl>
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Cc: freebsd-stable@freebsd.org, freebsd-alpha@freebsd.org
Subject: Re: 6.1-RELEASE panic / lockmgr?
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On Thu, 1 Jun 2006, Wilko Bulte wrote:

> My dual-CPU DS20 Alpha box can more or less consistently be
> forced into a panic like:
>
> FreeBSD/alpha (goldrush.wbnet) (ttyd0)^
>
> login: panic: lockmgr: thread 0xfffffc007d9d4a80, not exclusive lock holder
> 0xfffffc006052d260 unlocking
> cpuid = 1
> KDB: enter: panic
>
> Trigger is a "make -j2 release".  j2 seems to be needed, not seen it with
> -j1
>
> Unfortunately after printing the line with "KDB" the whole thing appears to 
> become completely catatonic :(

Try putting a call to critical_enter() towards the beginning of panic(). 
Sometimes this increases the reliability of entering the debugger by avoiding 
interrupt delivery during the process of entering.  If you want to be able to 
continue out, you'll need a critical_exit() at the end, but that generally 
isn't helpful for panic().

Robert N M Watson