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Date:      Thu, 25 Jan 2001 10:55:39 -0800 (PST)
From:      John Baldwin <jhb@FreeBSD.ORG>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        alpha@FreeBSD.ORG
Subject:   RE: cvs commit: src/sys/i386/i386 exception.s src/sys/kern kern_
Message-ID:  <XFMail.010125105539.jhb@FreeBSD.org>
In-Reply-To: <14959.33141.988328.39242@grasshopper.cs.duke.edu>

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On 25-Jan-01 Andrew Gallatin wrote:
> 
> John Baldwin writes:
>  > 
>  > On 24-Jan-01 John Baldwin wrote:
>  > > jhb         2001/01/24 13:59:25 PST
>  > > 
>  > >   Modified files:
>  > >     sys/i386/i386        exception.s 
>  > >     sys/kern             kern_fork.c 
>  > >     sys/sys              proc.h 
>  > >     sys/alpha/alpha      swtch.s trap.c vm_machdep.c 
>  > >   Log:
>  > >   - Change fork_exit() to take a pointer to a trapframe as its 3rd
> argument
>  > >     instead of a trapframe directly.  (Requested by bde.)
>  > >   - Convert the alpha switch_trampoline to call fork_exit() and use the
> MI
>  > >     fork_return() instead of child_return().
>  > >   - Axe child_return().
>  > 
>  > This should fix Drew's WITNESS panic as the mutex release of sched_lock
>  > by a forked child will be noticed by WITNESS now.
> 
> Bingo.   I'm now booting a WITNESS kernel.  Thanks for fixing this so
> quickly!

Actually, the fix was accidental, the real motivation was using the new MI fork
return code on the alpha. :)

> One last thing to point out -- when amd starts, I see this:
> 
> lock order reversal
>  1st vnode interlock last acquired @ ../../kern/vfs_vnops.c:644
>  2nd 0xfffffc000074d030 mntvnode @ ../../ufs/ffs/ffs_vfsops.c:940
>  3rd 0xfffffe0006a774c0 vnode interlock @ ../../ufs/ffs/ffs_vfsops.c:949

This is a problem that was present in the old VFS code with simplelocks, we
just haven't had tools to see this until now.  It doesn't hurt anything at the
moment.

> But it keeps on booting.  I'm running a fairly old world, so there may 
> be some sort of kernel / userland sync issue..
> 
> Drew

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.Baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/


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