2.5.50 hang when copying files, handwritten trace included

2.5.50 hung when copying 800M.
mke2fs on a 10G partition, then try to copy the entire /home there. Source and destionation was on the same disk. After a while, this happened:

EIP: wake_up_forked_process+0xb8/0x18c
EAX: 5a5a5a5a (suspicious)

trace:
do_fork
kernel_thread
pdflush
kernel_thread_helper
start_one_pdflush_thread
pdflush
__pdflush
__pdflush
background_writeout
kernel_thread_helper

The machine has 512M ram. It is a pentium IV 2.4GHz. The kernel is compiled with smp (hoping for hyperthreading but it haven't happened yet), preempt, devfs support (but devfs isn't mounted anywhere currently) and IDE driver for the SIS 5513.

Both filesystems are ext2. The machine was in single-user mode at the time. I can reliably reproduce this if a more detailed oops
will help in debugging. I have 2G of swap space on another IDE drive.

compiled with gcc 2.95.4 from debian testing

ide controller:
00:02.5 IDE interface: Silicon Integrated Systems [SiS] 5513 [IDE]

I'm using dma, irq unmasking, 32-bit io and multiple sector transfers.

Helge Hafting

Yes please - if you could gather sufficient info to enable us to determine what eax is pointing at in wake_up_forked_process(), that would help. Presumably it's the new process, which is rather bizarre.

Also, does disabling preemption make it stop?

Thanks.