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From: John Baldwin <jhb@freebsd.org>
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Cc: current@freebsd.org
Subject: Re: MTX Lock implementation question
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On Wednesday 04 March 2009 7:54:32 am Barney Cordoba wrote:
> 
> Suppose the following:
> 
> Module foo.c
> 
> foo_getlock(sc)
> {
>    FOO_LOCK(sc);
> }
> foo_unlock(sc)
> {
>    FOO_UNLOCK(sc);
> }
> foo_dosomething(sc)
> {
>    MTX_LOCK_ASSERT(sc);
>    foo_dooit();
> }
> 
> Module bar.c
> 
> bar_dofoo()
> {
>    foo_getlock(sc);
>    foo_dosomething(sc);
>    foo_unlock(sc);
> }

This works fine.
 
> Is this something that shouldn't work? I need to access functions
>  that require locks in a different module, but this code barfs on 
> ASSERT with witness enabled. Is this a deflugalty in WITNESS, or do 
> I need to create functions within foo that do the locking? Its been
> working ok for awhile (its not a high volume function) but when I 
> fired up witness to debug something else I encountered witness panics.

You probably have a real bug that WITNESS is warning about however.

-- 
John Baldwin