Re: Tracking down LORs

From: Roman Kurakin <rik_at_cronyx.ru>
Date: Fri, 20 Aug 2004 12:08:18 +0400
Robert Watson wrote:

>On Fri, 20 Aug 2004, Roman Kurakin wrote:
>
>  
>
>>	Currently I am trying to track down a couple of LORS in my code.
>>But it seems that I do not undestand smth or all things id realy so bad. 
>>    
>>
>
>I find it's very helpful to add lock orders to the hard-coded lock order
>table in subr_witness.c.  Without hard-coded entries, WITNESS will
>dynamically build an order based on observed lock use.  This is generally
>fine, but once in a while the "wrong" order will be used before the
>"right" order, so the lock order warning will print for the "right" order,
>leaving less useful debugging information.  The table allows the
>definition of partial orders, so you can specify relationships between
>subsets of mutexes of interest.  WITNESS will flesh out remaining orders
>through dynamic discovery.
>  
>
I'll try to go this way, since I am in dead end.

rik

>Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
>robert_at_fledge.watson.org      Principal Research Scientist, McAfee Research
>
>
>  
>
>>	So I want to ask some questions to find out if my thoughts
>>correct or wrong.
>>
>>1. If I am right LOR means that we have at least two mutexs.
>>Lets call them a and b. If we set a, then b in first case
>>and b then a in second we could get dead loop, and thus LOR.
>>
>>2. If I have some driver that have mutex a, and we have some
>>sytem code that could call this driver with Giant (b), we would
>>get LOR if driver lock a and some other part of system will
>>try to lock Giant?
>>
>>or I am wrong?
>>
>>rik
>>
>>
>>
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>>    
>>
>
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>  
>
Received on Fri Aug 20 2004 - 06:15:23 UTC

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