Hi,
I'm currently trying to debug some apparant IDE BM-DMA problem on the
NetWinder running 2.3.99-pre8, but I'm not getting very far with it.
The problem is random oopsen, or process killing due to invalid memory
accesses, eventually resulting in the machine dying.
(Note that this has been seen on the NetWinder running other 2.3.99 kernels)
I've tried flushing the caches within the ide-dma code to ensure that there
isn't a problem there, and I've even disabled all the caches in the machine
via the CPUs control register, so I don't think its a cache coherency
problem. It could be a PCI problem, but the problem does not appear to
occur on 2.2.14 kernels.
My test is:
while (true); do hdparm -t /dev/hda; done
and to leave that running for about 5 minutes on a 64MB machine.
One of the more common oopsen (cut down to the bare essentials) is
from within __remove_from_free_list:
Unable to handle kernel NULL pointer dereference at virtual address 00000024
pc : [<c0068638>] lr : [<c0068fd4>] within __remove_from_free_list
Process hdparm (pid: 126, stackpage=c3cdb000)
Function entered at [<c0068604>] from [<c0068fd4>] __remove_from_free_list
Function entered at [<c0068f7c>] from [<c006fedc>] getblk
Function entered at [<c006fbb0>] from [<c0066810>] block_read
Function entered at [<c00666d0>] from [<c002de00>] sys_read
The NULL pointer in question is bh->b_next_free, which is part of the
following line in fs/buffer.c:__remove_from_free_list:
bh->b_next_free->b_prev_free = bh->b_prev_free;
Is this a known problem with 2.3.99-pre8, or could it be a possible problem?
Is anyone willing to say outright that this could not be a generic kernel bug?
I'd like to know this just so that I don't spend the rest of today chasing
an already known about-to-be-fixed bug.
Thanks.
_____
|_____| ------------------------------------------------- ---+---+-
| | Russell King rmk@arm.linux.org.uk --- ---
| | | | http://www.arm.linux.org.uk/~rmk/aboutme.html / / |
| +-+-+ --- -+-
/ | THE developer of ARM Linux |+| /|\
/ | | | --- |
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