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List:       netbsd-tech-kern
Subject:    Re: Weird LOCKDEBUG error in revivesa
From:       Bill Stouder-Studenmund <wrstuden () NetBSD ! org>
Date:       2008-06-28 21:01:57
Message-ID: 20080628210157.GD2796 () netbsd ! org
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On Fri, Jun 27, 2008 at 02:18:24PM -0700, Bill Stouder-Studenmund wrote:
> I've got the wrstuden-revivesa branch to where kernels boot and almost 
> work. A test program is running into an error that is "letting" me debug 
> error handling.
> 
> I'm running into a LOCKDEBUG error that makes no sense:
> 
>         printf("About to destroy sa_mutex %p\n", &sa->sa_mutex);
>         mutex_destroy(&sa->sa_mutex);
>         printf("Did destroy sa_mutex %p\n", &sa->sa_mutex);
>         pool_put(&sadata_pool, sa); 
> 
> is triggering a lockdebug error that "sa" contains a still-active lock. 
> I'm attaching a screen shot of the problem seen running in VM Fusion. The 
> deal is that the lock that's causing the problem, 0xcbbe6f78, is the very 
> lock that was passed to mutex_destroy(). I have printfs before and after 
> the destroy showing that it sure looks like it was zapped.

Turns out the problem was there was a mutex_init() call followed by a 
memset(sa, 0, sizeof(*sa)) call sequence. That wiped out MUTEX_BIT_DEBUG 
in the mutex, which caused the mutex_destroy() code to not tell the 
lockdebug code about the destroy, since it thought the mutex wasn't being 
debugged.

Take care,

Bill

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