Re: [1/3] 2.6.22-rc3: known regressions v2

[Miklos Szeredi <miklos@szeredi.hu>]

> i have no better ideas that what you already tried - but unfortunately 
> the tracer makes the bug go away and the NMI watchdog crashes your box. 
> Btw., nmi_watchdog=2 might have a higher chance of surviving (it can 
> still lock up a T60 but with a lower likelyhood).

Good tip, nmi_watchdog=2 worked.  Unlike the previous freezes, after
this one it didn't continue after some minutes.  Don't know if that's
because the NMI oopser changed something, or if this is a slightly
different lockup...

No serial port on this laptop, so screenshot done with digicam:

  http://www.kernel.org/pub/linux/kernel/people/mszeredi/freeze/nmioops.jpg

Here are the transcribed stack traces:

CPU1
process: strace
 _spin_lock
 task_rq_lock
 wait_task_inactive
 ptrace_check_attach
 sys_ptrace

CPU0
process: fusexmp_fh (this is one of several similar threads being straced)
 _spin_lock_irq
 schedule
 ptrace_stop
 ptrace_notify
 syscall_trace
 syscall_trace_enter
 tracesys

Both these seem to be spinning on rq->lock, but who is holding this
lock?

Miklos
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