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Date:      Fri, 22 Nov 2002 11:44:38 -0500 (EST)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Juli Mallett <jmallett@FreeBSD.org>
Cc:        freebsd-current@FreeBSD.org, Juli Mallett <jmallett@NewGold.NET>, Robert Watson <rwatson@FreeBSD.org>
Subject:   Re: VM locking problem... And doscmd(8)
Message-ID:  <XFMail.20021122114438.jhb@FreeBSD.org>
In-Reply-To: <20021121185414.A83098@FreeBSD.org>

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On 22-Nov-2002 Juli Mallett wrote:
> * De: Robert Watson <rwatson@FreeBSD.org> [ Data: 2002-11-21 ]
>       [ Subjecte: Re: VM locking problem... And doscmd(8) ]
>> On Thu, 21 Nov 2002, Juli Mallett wrote:
>> 
>> > I'm getting a giant owned assertion failure in the vm_map code, simply
>> > by running "doscmd something.exe" where something.exe is a
>> > self-extracting ZIP file (of BIOS upgrade stuff, FWIW), which leads
>> > trivially to tripping over it.  I still don't have a good way to get the
>> > trace output from the box in question to here, but I've been able to
>> > reproduce it every time, so it shouldn't be hard for someone else. 
>> > 
>> > I rebuilt my kernel today from CVSup, but hadn't tried before that. 
>> 
>> For those of us that don't frequently (ever) use doscmd -- can you provide
>> a tarball of the necessary configuration files, executable, etc,
>> somewhere? 
> 
> I don't (ever) either, and am doing this without a config file (as far as
> I'm aware anyway), and using the following executable:
> 
> http://people.freebsd.org/~jmallett/boom.exe

There is some discussion on IRC, and Maxime is working on a fix.  The
problem is that if you use a TSS (for /dev/io or some such) then the
TSS gets kmem_free()'d in cpu_thread_exit().  However, cpu_thread_exit()
is a particularly bad time to be calling kmem_free() as you are holding
sched_lock in a critical section w/o any sleep mutexes when it is called.
:)  The solution I've discussed with Maxime is to create a
cpu_thread_dtor() callout called from thread_dtor() (which is called when
a thread is free()'d) and to move the kmem_free() of the TSS into
that function instead.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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