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Date: Wed, 7 Aug 2002 14:08:55 -0700
From: Jesse Barnes <jbarnes@sgi.com>
To: Rik van Riel <riel@conectiva.com.br>
Cc: linux-kernel@vger.kernel.org, jmacd@namesys.com, phillips@arcor.de,
       rml@tech9.net
Subject: Re: [PATCH] lock assertion macros for 2.5.30
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On Wed, Aug 07, 2002 at 06:02:19PM -0300, Rik van Riel wrote:
> On Wed, 7 Aug 2002, Jesse Barnes wrote:
> 
> > +++ linux-2.5.30-lockassert/drivers/scsi/scsi.c Wed Aug  7 11:35:32 2002
> > @@ -262,7 +262,7 @@
> 
> > +        MUST_NOT_HOLD(q->queue_lock);
> 
> ...
> 
> > +#if defined(CONFIG_DEBUG_SPINLOCK) && defined(CONFIG_SMP)
> > +#define MUST_HOLD(lock)			BUG_ON(!spin_is_locked(lock))
> > +#define MUST_NOT_HOLD(lock)		BUG_ON(spin_is_locked(lock))
> 
> Please tell me the MUST_NOT_HOLD thing is a joke.
> 
> What is to prevent another CPU in another code path
> from holding this spinlock when the code you've
> inserted the MUST_NOT_HOLD in is on its merry way
> not holding the lock ?

Nothing at all, but isn't that how the scsi ASSERT_LOCK(&lock, 0)
macro worked before?  I could just remove all those checks in the scsi
code I guess.

After I posted the last patch, a few people asked for MUST_NOT_HOLD so
I added it back in.  Do you think it's a bad idea?  See the last
thread if you're curious (Joshua's comments in particular):
http://marc.theaimsgroup.com/?t=102764009400001&r=1&w=2

Thanks,
Jesse
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