[uml-devel] Errors in schedule / _switch_to

["Oscar Hellström" <oscar@hellstrom.st>]

Hi,

I'm running an older version of the kernel, 2.6.32.3 and I'm experiencing
segmentations faults in _switch_to, which is called from schedule. My
stacktrace looks like:
3 <signal handler called>
#14 _switch_to (prev=0x43ff1340, next=0xffffffd4, last=0x43ff1340) at
arch/um/kernel/process.c:82
#15 0x08205cd9 in schedule () at kernel/sched.c:2886
#16 0x08205dda in io_schedule () at kernel/sched.c:6784
#17 0x0809af72 in sync_page (word=0x96ba180) at mm/filemap.c:187
#18 0x08205fde in __wait_on_bit_lock (wq=0x980b7d8, q=0x43fd5ce4,
action=0x809af37 <sync_page>, mode=2) at kernel/wait.c:229
#19 0x0809af21 in __lock_page (page=0x96ba180) at mm/filemap.c:601
#20 0x0809afbd in find_lock_page (mapping=0x47608668, offset=2596) at
include/linux/pagemap.h:317
#21 0x0809c888 in filemap_fault (vma=0x43d70764, vmf=0x43fd5d8c) at
mm/filemap.c:1538
#22 0x080a88ad in __do_fault (mm=0x478855e0, vma=0x43d70764,
address=2437412980, pmd=0x472c0914, pgoff=2596, flags=0, 
orig_pte={pte = 0}) at mm/memory.c:2719
#23 0x080a9fec in handle_mm_fault (mm=0x478855e0, vma=0x43d70764,
address=2437412980, flags=0) at mm/memory.c:2917
#24 0x0805c5f1 in handle_page_fault (address=2437412980, ip=1076410045,
is_write=0, is_user=1, code_out=0x43fd5e40)
at arch/um/kernel/trap.c:71
#25 0x0805c729 in segv (fi={error_code = 4, cr2 = 2437412980, trap_no =
14}, ip=1076410045, is_user=1, regs=0x43ff1550)
at arch/um/kernel/trap.c:178
#26 0x0805c91e in segv_handler (sig=11, regs=0x43ff1550) at
arch/um/kernel/trap.c:150
#27 0x0806c00a in userspace (regs=0x43ff1550) at
arch/um/os-Linux/skas/process.c:421
#28 0x0805aa75 in fork_handler () at arch/um/kernel/process.c:179
#29 0x00000000 in ?? ()

I've compiled in a driver into the kernel which fakes interrupts by sending
signals to the UML process. I guess this could interfere with something,
but I do believe I've seen this without the signals being enabled.
Unfortunately I don't have any easy way to reproduce this, it usually
happens seemingly at random.

Any pointer to what this can be and where I can start looking would be
appreciated!

Thanks
/Oscar
-- 
Oscar Hellström, oscar@hellstrom.st
web: http://oscar.hellstrom.st
xmpp: oscar@hellstrom.st

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