Strange Oops with 2.4.20 and ISDN Channel bundling

Patrick McHardy (kaber@trash.net)
Fri, 14 Mar 2003 15:39:18 +0100


Hi,
we receive the following oops reproducible with vanilla 2.4.20 and isdn
channel bundling:

Oops: 0007
CPU: 0
EIP: 0023:[<0804b6e7>] Not tainted
EFLAGS: 00010287
eax: 080d7940 ebx: 080d7958 ecx: 3fdd2b14 edx: 3fdd2bb4
esi: 0806c204 edi: 00000001 ebp: bffffdc8 esp: bffff7a0
ds: 002b es: 002b ss: 002b
Process ipppd (pid: 1001, stackpage=cded5000)
<0>Kernel panic: Aiee, killing interrupt handler!
In interrupt handler - not syncing

No backtrace is displaced. We had to linux machines connected, only the
one sending data
oopses. Before it happens "Warning: kfree_skb on hard IRQ d08342a4" is
logged a couple of times.
We first noticed the oops with a heavily patched kernel we use. With
this kernel, all kinds of
BUG()s were hit, f.e. in schedule() and alloc_skb(), both expected
in_interrupt() to be false.

The alloc_skb BUG() looks like this:
kernel BUG at skbuff.c:174!
invalid operand: 0000
CPU: 0
EIP: 0010:[<c02204e8>] Not tainted
Using defaults from ksymoops -t elf32-i386 -a i386
EFLAGS: 00010286
eax: 0000003a ebx: 00000000 ecx: cd674000 edx: 00000001
esi: 000001f0 edi: c8f5f4c0 ebp: cd6a8000 esp: cd6a9ddc
ds: 0018 es: 0018 ss: 0018
Process ipppd (pid: 876, stackpage=cd6a9000)
Stack: c02a8580 c021f894 000001f0 00000000 c021f894 00000078 000001f0
00000000
c8f5f4c0 00000078 00000000 c8f5fb80 c021f99b c8f5f4c0 00000078
00000000
00000000 cd6a9e48 c02676f4 c8f5f4c0 00000078 00000000 cd6a9e48
c8f5fbc8
Call Trace: [<c021f894>] [<c021f894>] [<c021f99b>] [<c02676f4>]
[<c021d48c>]
[<c0118740>] [<c021e20b>] [<d0836bb6>] [<c022f03f>] [<c0224a34>]
[<c011c7d9>]
[<c0108421>] [<c021e24d>] [<c021e949>] [<c01070d3>]
Code: 0f 0b ae 00 20 85 2a c0 58 5a e9 7c fe ff ff 90 90 8d b4 26


>>EIP; c02204e8 <alloc_skb+1a8/1c0> <=====

>>ecx; cd674000 <_end+d30dc54/104acc54>
>>edi; c8f5f4c0 <_end+8bf9114/104acc54>
>>ebp; cd6a8000 <_end+d341c54/104acc54>
>>esp; cd6a9ddc <_end+d343a30/104acc54>

Trace; c021f894 <sock_alloc_send_pskb+b4/1a0>
Trace; c021f894 <sock_alloc_send_pskb+b4/1a0>
Trace; c021f99b <sock_alloc_send_skb+1b/20>
Trace; c02676f4 <unix_stream_sendmsg+124/2e0>
Trace; c021d48c <sock_sendmsg+5c/90>
Trace; c0118740 <printk+f0/130>
Trace; c021e20b <sys_sendto+cb/f0>
Trace; d0836bb6 <[isdn]isdn_net_start_xmit+196/2e0>
Trace; c022f03f <qdisc_restart+6f/d0>
Trace; c0224a34 <net_tx_action+74/a0>
Trace; c011c7d9 <do_softirq+99/a0>
Trace; c0108421 <do_IRQ+a1/b0>
Trace; c021e24d <sys_send+1d/30>
Trace; c021e949 <sys_socketcall+e9/1b0>
Trace; c01070d3 <system_call+33/40>

Code; c02204e8 <alloc_skb+1a8/1c0>
00000000 <_EIP>:
Code; c02204e8 <alloc_skb+1a8/1c0> <=====
0: 0f 0b ud2a <=====
Code; c02204ea <alloc_skb+1aa/1c0>
2: ae scas %es:(%edi),%al
Code; c02204eb <alloc_skb+1ab/1c0>
3: 00 20 add %ah,(%eax)
Code; c02204ed <alloc_skb+1ad/1c0>
5: 85 2a test %ebp,(%edx)
Code; c02204ef <alloc_skb+1af/1c0>
7: c0 58 5a e9 rcrb $0xe9,0x5a(%eax)
Code; c02204f3 <alloc_skb+1b3/1c0>
b: 7c fe jl b <_EIP+0xb>
Code; c02204f5 <alloc_skb+1b5/1c0>
d: ff (bad)
Code; c02204f6 <alloc_skb+1b6/1c0>
e: ff 90 90 8d b4 26 call *0x26b48d90(%eax)

<0>Kernel panic: Aiee, killing interrupt handler!

To me it looks like something in the area of isdn_net_start_xmit does
something
so in_interrupt later returns true when it is not supposed to do so (all
unix socket
handling should be done in user context if i understand correctly).
I'm not sure what this would be, is it correct to look for:

- *_lock_bk() without *_unlock_bh()
- local_bh_disable() without local_bh_enable()
- save_flags(), sti() without restore_flags()

Am i missing some ? Any other suggestions would be welcome, too.

Regards,
Patrick

Additional Information:
Gnu C 3.2
Gnu make 3.79.1
binutils 2.11.2
util-linux 2.11w
mount 2.11w
modutils 2.4.19
e2fsprogs 1.29
reiserfsprogs 3.x.1b
pcmcia-cs 3.2.4
PPP 2.4.1
isdn4k-utils 3.2p1
Linux C Library 2.2.5
Dynamic linker (ldd) 2.2.5
Linux C++ Library 5.0.0
Procps 2.0.9
Net-tools 1.60
Kbd 1.06
Sh-utils 2.0

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