kernel thread and NULL active_mm (MPC860)

kernel thread and NULL active_mm (MPC860)

[Lee Rhodes]

Hi,
Can anyone tell me what would cause my kernel thread to have a NULL
active_mm? The thread is waking up from a down_interruptible (it's a DPC
thread) and, in doing so, it triggers the BUG_ON on line 559 of sched.c.

I'm just wondering if anyone can provide me with some theories on what might
be going wrong. The same could runs fine on an i386 Linux desktop machine.
I'm only encountering this issue when I port it to MPC860.

Thanks for any tips,
Lee


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Re: kernel thread and NULL active_mm (MPC860)

[Dan Malek]

On May 14, 2004, at 11:20 AM, Lee Rhodes wrote:

> Can anyone tell me what would cause my kernel thread to have a NULL
> active_mm?

Good question.  The active_mm is used by lazy TLB management, which
we don't do on PowerPC.  We don't use this data structure field for any
of our MMU processing.  It's managed by generic code in the scheduler
and process management functions, there isn't any PowerPC specific
code that uses or changes it.  I thought at one time I traced a path
through
the scheduler that would cause active_mm to be NULL for kernel threads
under certain conditions, but since we didn't use it, I didn't care.
That
code always make my head hurt.

It would help if you indicate what versions of kernel you are using in
both cases and where you got them.

Thanks.


	-- Dan


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Re: kernel thread and NULL active_mm (MPC860)

[Lee Rhodes]

Hi Dan,
Thanks for taking up the gauntlet.

>It would help if you indicate what versions of kernel you are using in both
>cases and where you got them.
On my PPC-based hardware, I'm using 2.4.19 which I got from kernel.org. The
same code works fine on an i386-based desktop machine running various
kernels including 2.4.18, 2.4.20 and 2.4.21.

Lee


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