Re: [PATCH] kthread conversion: convert ieee1394 from kernel_thread

[Stefan Richter <stefanr@s5r6.in-berlin.de>]

I wrote:
> I will try to rework this patch

While doing so I discovered an old bug which happens with current code 
as well as with Linux 2.6.16.x and 2.6.15.x, maybe also on older kernels:

When "modprobe ohci1394" is followed shortly by "modprobe -r ohci1394" 
(say, 1 second after the previous modprobe finished), one of the 
following may happen:
  - kernel panic due to exception in interrupt
    (happened on 2.6.15.x preempt uniprocessor)
    or
  - modprobe -r hangs in D state, as does knodemgrd_0
    (happened on 2.6.16.x preempt SMP on a uniprocessor machine).

I have two FireWirew host adapters installed. The knodemgrd_1 slept 
interruptibly (S state) while the other slept uninterruptibly (D state) 
right after modprobe -r was issued. This happens with or without other 
nodes attached to the FireWire ports. Host adapters are based on a TI 
1394b chip (host 0) and on a VIA 1394a chip (host 1).

"All's right with the world" if a longer pause is put between modprobe 
and modprobe -r, say 4 seconds.

(I will add a bugzilla entry and try to resolve this eventually...)
-- 
Stefan Richter
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http://arcgraph.de/sr/