Re: WITNESS bug

From: Julian Elischer <julian_at_elischer.org>
Date: Tue, 19 Oct 2004 16:16:19 -0700
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. :)
>

now that we have read-write locks it may be worth re looking at teh 
netgraph version
of same to see if they can be used instead, but I doubt that the generic 
ones would be as
lightweight.

>
>  
>
Received on Tue Oct 19 2004 - 21:16:19 UTC

This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:38:18 UTC