From owner-freebsd-smp  Wed Mar 10 11:12: 1 1999
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From: "Kenneth D. Merry" <ken@plutotech.com>
Message-Id: <199903101910.MAA09630@panzer.plutotech.com>
Subject: Re: lockmgr() panic
In-Reply-To: <199903101850.KAA56970@apollo.backplane.com> from Matthew Dillon at "Mar 10, 1999 10:50:36 am"
To: dillon@apollo.backplane.com (Matthew Dillon)
Date: Wed, 10 Mar 1999 12:10:45 -0700 (MST)
Cc: Thierry.Besancon@lps.ens.fr, luoqi@watermarkgroup.com,
	Thierry.Besancon@tournesol.lps.ens.fr, dwhite@gdi.uoregon.edu,
	freebsd-smp@FreeBSD.ORG, Pierre.David@prism.uvsq.fr, alc@cs.rice.edu,
	jt@ratp.fr
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Matthew Dillon wrote...
> 
> :>> This is a completely different problem. 
> :
> :Life sucks today.
> :
> :Reading src/sys/kern/kern_lock.c, I saw this piece of code that might
> :be relevant with this problem :
> :
> :#if !defined(MAX_PERF) 
> :                        if ((extflags & LK_CANRECURSE) == 0)
> :                                panic("lockmgr: locking against myself"); 
> :#endif 
> :
> :Before defining the flag, does anybody know what MAX_PERF implies
> :other than not panicing the kernel ? What does it means ?
> 
>     MAX_PERF means 'maximum performance'.  Note that the conditional 
>     is an '#if !defined ...' conditional, not an '#if defined ...'
>     conditional.  
> 
>     This means that by default, when MAX_PERF is *not* defined, the above
>     code *will* be executed.
> 
>     If MAX_PERF is defined, the system removes many sanity checks from the
>     kernel that would otherwise be compiled in.  I would recommend that you
>     *NOT* define it.
> 
> 						-Matt

I'll second this.  One of the few times I've really seriously hosed my
filesystem came one time a couple of years ago (Summer '97) when I defined
MAX_PERF.

Even during the early CAM development, I never managed to hose my
filesystem, but defining MAX_PERF was a really bad idea.

I think that's one of those "John-Dyson-only" options.

Ken
-- 
Kenneth Merry
ken@plutotech.com


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