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Date:      Tue, 19 Oct 2004 15:03:26 -0700
From:      Julian Elischer <julian@elischer.org>
To:        John Baldwin <jhb@freebsd.org>
Cc:        Kris Kennaway <kris@obsecurity.org>
Subject:   Re: WITNESS bug
Message-ID:  <41758F2E.3060706@elischer.org>
In-Reply-To: <200410191729.42330.jhb@FreeBSD.org>
References:  <20041019023713.GA1072@green.homeunix.org> <200410191650.28544.jhb@FreeBSD.org> <4175862C.6030403@elischer.org> <200410191729.42330.jhb@FreeBSD.org>

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John Baldwin wrote:

>On Tuesday 19 October 2004 05:25 pm, Julian Elischer wrote:
>  
>
>>John Baldwin wrote:
>>    
>>
>>>On Tuesday 19 October 2004 12:01 pm, Kris Kennaway wrote:
>>>      
>>>
>>>>On Tue, Oct 19, 2004 at 09:13:26AM -0400, Robert Huff wrote:
>>>>        
>>>>
>>>>>Brian Fundakowski Feldman writes:
>>>>>          
>>>>>
>>>>>>You should never not run with WITNESS_SKIPSPIN if you use
>>>>>>modules.  Any spin mutexes not listed statically in the witness
>>>>>>code will cause your machine to immediately panic.
>>>>>>            
>>>>>>
>>>>>	If this is true (and I'm not disputing it), shouldn't it be
>>>>>noted in GENERIC and/or NOTES?  For that matter, what's the penalty
>>>>>for not automatically including it as part of WITNESS?
>>>>>          
>>>>>
>>>>Sometimes you don't want to use it, e.g. if you actually want to trace
>>>>spinlock operations with witness.
>>>>        
>>>>
>>>True spin mutexes should be rarely used anyways, so I don't think modules
>>>needing spin mutexes is all that big of an issue.  Almost all mutexes
>>>should just be regular mutexes.
>>>      
>>>
>>netgraph uses a spin mutex for it's node locks
>>    
>>
>
>This is likely a bug, esp. given that normal mutexes adaptively spin when it 
>is advantageous to do so. :)
>  
>
it assumes it's not going to sleep..

>
>  
>



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