[uml-devel] Errors in schedule / _switch_to

[uml-devel] Errors in schedule / _switch_to

[Oscar Hellström]

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:
...
#13 <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 happens
seemingly at random.

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

Thanks
/Oscar

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[uml-devel] Errors in schedule / _switch_to

[Oscar Hellström]

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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Osterman Research conducted this study that outlines how and why cloud
computing security and archiving is rapidly being adopted across the IT 
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reliability. Learn more. http://www.accelacomm.com/jaw/sfnl/114/51425301/
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Re: [uml-devel] Errors in schedule / _switch_to

[richard -rw- weinberger]

2011/9/9 Oscar Hellström <oscar@hellstrom.st>:
>
> Any pointer to what this can be and where I can start looking would be
> appreciated!
>

Does with also happen with a vanilla kernel?
Do you have a full trace? The value of EIP would be helpful.

-- 
Thanks,
//richard

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Re: [uml-devel] Errors in schedule / _switch_to

[Oscar Hellström]

Hi,

I don't think I can reproduce this on a vanilla kernel, but I can't run my
application without my driver (and some other changes).

bt full gives me:
....
#13 <signal handler called>
No symbol table info available.
#14 _switch_to (prev=0x43ff1340, next=0xffffffd4, last=0x43ff1340) at
arch/um/kernel/process.c:82
from = (struct task_struct *) 0x43ff1340
to = (struct task_struct *) 0xffffffd4
#15 0x08205cd9 in schedule () at kernel/sched.c:2886
prev = (struct task_struct *) 0x43ff1340
next = (struct task_struct *) 0xffffffd4
switch_count = (long unsigned int *) 0x43ff14c8
#16 0x08205dda in io_schedule () at kernel/sched.c:6784
No locals.
#17 0x0809af72 in sync_page (word=0x96ba180) at mm/filemap.c:187
mapping = (struct address_space *) 0x0
#18 0x08205fde in __wait_on_bit_lock (wq=0x980b7d8, q=0x43fd5ce4,
action=0x809af37 <sync_page>, mode=2) at kernel/wait.c:229
ret = 158048640
#19 0x0809af21 in __lock_page (page=0x96ba180) at mm/filemap.c:601
wait = {key = {flags = 0x96ba180, bit_nr = 0}, wait = {flags = 1, private =
0x43ff1340, 
func = 0x8086ef9 <wake_bit_function>, task_list = {next = 0x980b7d8, prev =
0x980b7d8}}}
#20 0x0809afbd in find_lock_page (mapping=0x47608668, offset=2596) at
include/linux/pagemap.h:317
page = (struct page *) 0x96ba180
#21 0x0809c888 in filemap_fault (vma=0x43d70764, vmf=0x43fd5d8c) at
mm/filemap.c:1538
error = 0
file = (struct file *) 0x473b8ba0
mapping = (struct address_space *) 0x47608668
ra = (struct file_ra_state *) 0x473b8be0
inode = (struct inode *) 0x476085cc
offset = 2596
page = (struct page *) 0x0
ret = 4
#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
page = <value optimized out>
anon = <value optimized out>
dirty_page = <value optimized out>
vmf = {flags = 0, pgoff = 2596, virtual_address = 0x9147f000, page = 0x0}
ret = 115
page_mkwrite = <value optimized out>
#23 0x080a9fec in handle_mm_fault (mm=0x478855e0, vma=0x43d70764,
address=2437412980, flags=0) at mm/memory.c:2917
pgd = (pgd_t *) 0x472c0914
pte = (pte_t *) 0x404551fc
#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
fault = 0
mm = (struct mm_struct *) 0x478855e0
vma = (struct vm_area_struct *) 0x43d70764
err = <value optimized out>
#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
si = {si_signo = 0, si_errno = 0, si_code = 196610, _sifields = {_pad = {0
<repeats 27 times>, 14, 16157}, _kill = {
_pid = 0, _uid = 0}, _timer = {_tid = 0, _overrun = 0, _pad = 0x43fd5e4c
"", _sigval = {sival_int = 0, 
sival_ptr = 0x0}, _sys_private = 0}, _rt = {_pid = 0, _uid = 0, _sigval =
{sival_int = 0, sival_ptr = 0x0}}, 
_sigchld = {_pid = 0, _uid = 0, _status = 0, _utime = 0, _stime = 0},
_sigfault = {_addr = 0x0, _addr_lsb = 0}, 
_sigpoll = {_band = 0, _fd = 0}}}
catcher = <value optimized out>
err = <value optimized out>
address = <value optimized out>
#26 0x0805c91e in segv_handler (sig=11, regs=0x43ff1550) at
arch/um/kernel/trap.c:150
fi = <value optimized out>
#27 0x0806c00a in userspace (regs=0x43ff1550) at
arch/um/os-Linux/skas/process.c:421
sig = <value optimized out>
timer = {it_interval = {tv_sec = 0, tv_usec = 0}, it_value = {tv_sec = 0,
tv_usec = 16001}}
nsecs = 1315569399711559000
err = <value optimized out>
status = 2943
op = <value optimized out>
pid = 16157
local_using_sysemu = 2
#28 0x0805aa75 in fork_handler () at arch/um/kernel/process.c:179
No locals.
#29 0x00000000 in ?? ()
No symbol table info available.


Stack level 14, frame at 0x43fd5c74:
eip = 0x805a900 in _switch_to (arch/um/kernel/process.c:82); saved eip
0x8205cd9
called by frame at 0x43fd5ca4, caller of frame at 0x43fd5c60
source language c.
Arglist at 0x43fd5c6c, args: prev=0x43ff1340, next=0xffffffd4,
last=0x43ff1340
Locals at 0x43fd5c6c, Previous frame's sp is 0x43fd5c74
Saved registers:
ebx at 0x43fd5c64, ebp at 0x43fd5c6c, esi at 0x43fd5c68, eip at 0x43fd5c70

Thanks
/Oscar 

On Sat, 10 Sep 2011 13:10:09 +0200, richard -rw- weinberger
<richard.weinberger@gmail.com> wrote:
> 2011/9/9 Oscar Hellström <oscar@hellstrom.st>:
>>
>> Any pointer to what this can be and where I can start looking would be
>> appreciated!
>>
> 
> Does with also happen with a vanilla kernel?
> Do you have a full trace? The value of EIP would be helpful.

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

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