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Date:      Wed, 4 Mar 2009 10:13:22 -0500
From:      John Baldwin <jhb@freebsd.org>
To:        freebsd-current@freebsd.org, barney_cordoba@yahoo.com
Cc:        current@freebsd.org
Subject:   Re: MTX Lock implementation question
Message-ID:  <200903041013.22496.jhb@freebsd.org>
In-Reply-To: <142283.66010.qm@web63903.mail.re1.yahoo.com>
References:  <142283.66010.qm@web63903.mail.re1.yahoo.com>

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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



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