On 05/07/2012 06:24 PM, Gilles Chanteperdrix wrote:
> On 05/08/2012 02:59 AM, Doug Brunner wrote:
>> I just got an oops from running one of my POSIX skin RT applications:
>>
>>      [183168.735823] BUG: unable to handle kernel paging request at 00700bf5
>>      [183168.737436] IP: [<c10c091f>] xnheap_init+0x1cf/0x210
>>      [183168.738604] *pde = 00000000
>>      [183168.739406] Oops: 0002 [#1] PREEMPT
>>      [183168.740173] last sysfs file: /sys/devices/virtual/bdi/0:19/uevent
>>      [183168.740173] Modules linked in: e1000 xeno_rtipc lxfb cfbcopyarea
>> cfbimgblt cfbfillrect binfmt_misc psmouse usbhid serio_raw hid ata_piix
>> [last unloaded: e1000]
>>      [183168.740173]
>>      [183168.740173] Pid: 2557, comm: eve_dal Not tainted 2.6.37 #1 /Bochs
>>      [183168.740173] EIP: 0060:[<c10c091f>] EFLAGS: 00010246 CPU: 0
>>      [183168.740173] EIP is at xnheap_init+0x1cf/0x210
>>      [183168.740173] EAX: 00700bf1 EBX: eed0e210 ECX: eed0e730 EDX: eed0e2fc
>>      [183168.740173] ESI: 00000000 EDI: 00000000 EBP: eed27da4 ESP: eed27d7c
>>      [183168.740173]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
>>      [183168.740173] Process eve_dal (pid: 2557, ti=eed26000
>> task=f5773280 task.ti=eed26000)
>>      [183168.740173] I-pipe domain Linux
>>      [183168.740173] Stack:
>>      [183168.740173]  eed0e304 00000030 c157d4a9 eed0e210 eed0e2fc
>> eed0e2fc 0000003e 00000000
>>      [183168.740173]  f85ea000 eed0e210 eed27dc8 c10c0c44 00001000
>> 00000000 f85aa000 00040000
>>      [183168.740173]  eed0e200 fffffff4 eed0e210 eed27df0 c10cf198
>> eed27de4 c1058b86 eed27f20
>>      [183168.740173] Call Trace:
>>      [183168.740173]  [<c10c0c44>] ? xnheap_init_mapped+0xd4/0x210
>>      [183168.740173]  [<c10cf198>] ? xnshadow_sys_event+0x68/0x210
>>      [183168.740173]  [<c1058b86>] ? commit_creds+0xe6/0x190
>>      [183168.740173]  [<c10cefa3>] ? xnshadow_sys_bind+0x293/0x420
>>      [183168.740173]  [<c114b22e>] ? __d_lookup+0x12e/0x160
>>      [183168.740173]  [<c114bf96>] ? dput+0x66/0x1b0
>>      [183168.740173]  [<c1141b9e>] ? path_to_nameidata+0x1e/0x50
>>      [183168.740173]  [<c1143e02>] ? link_path_walk+0x422/0x7c0
>>      [183168.740173]  [<c11425f5>] ? path_put+0x25/0x30
>>      [183168.740173]  [<c109559d>] ? __ipipe_restore_root+0x1d/0x30
>>      [183168.740173]  [<c112d537>] ? kmem_cache_free+0xa7/0x100
>>      [183168.740173]  [<c11423ea>] ? putname+0x2a/0x40
>>      [183168.740173]  [<c1144cfa>] ? user_path_at+0x4a/0x80
>>      [183168.740173]  [<c10cd82d>] ? losyscall_event+0xad/0x200
>>      [183168.740173]  [<c1095035>] ? __ipipe_dispatch_event+0xb5/0x170
>>      [183168.740173]  [<c10cd780>] ? losyscall_event+0x0/0x200
>>      [183168.740173]  [<c10166d5>] ? __ipipe_syscall_root+0x45/0xd0
>>      [183168.740173]  [<c145526d>] ? system_call+0x2d/0x53
>>      [183168.740173] Code: 24 e8 a6 cc 19 00 fa 8b 0d 28 36 61 c1 0f ba
>> 2d c0 1b 61 c1 00 19 f6 8b 55 e8 83 e6 01 89 8b f0 00 00 00 8b 01 89 83
>> ec 00 00 00<89>   50 04 31 c0 89 11 8b 15 c0 1b 61 c1 83 05 2c 36 61 c1 01 83
>>      [183168.740173] EIP: [<c10c091f>] xnheap_init+0x1cf/0x210 SS:ESP
>> 0068:eed27d7c
>>      [183168.740173] CR2: 0000000000700bf5
>>
>> As you can see, this happened with kernel 2.6.37, and I built it with
>> Xenomai 2.6.0. The offending instruction was at xnheap_init + 463:
>>
>>      0xc10c090b<xnheap_init+443>: mov    -0x18(%ebp),%edx
>>      0xc10c090e<xnheap_init+446>: and    $0x1,%esi
>>      0xc10c0911<xnheap_init+449>: mov    %ecx,0xf0(%ebx)
>>      0xc10c0917<xnheap_init+455>: mov    (%ecx),%eax
>>      0xc10c0919<xnheap_init+457>: mov    %eax,0xec(%ebx)
>>      0xc10c091f<xnheap_init+463>: mov    %edx,0x4(%eax)
>>      0xc10c0922<xnheap_init+466>: xor    %eax,%eax
>>      0xc10c0924<xnheap_init+468>: mov    %edx,(%ecx)
>>      0xc10c0926<xnheap_init+470>: mov    0xc1611bc0,%edx
>>      0xc10c092c<xnheap_init+476>: addl   $0x1,0xc161362c
>>      0xc10c0933<xnheap_init+483>: addl   $0x1,0xc17c83e4
>>
>> This corresponds to ath(xnholder_t *, xnholder_t *) in
>> include/xenomai/nucleus/queue.h, line 48:
>>
>>      43 static inline void ath(xnholder_t *head, xnholder_t *holder)
>>      44 {
>>      45 /* Inserts the new element right after the heading one  */
>>      46 holder->last = head;
>>      47 holder->next = head->next;
>>      48 holder->next->last = holder;
>>      49 head->next = holder;
>>      50 }
>>
>> It's apparently the call to appendq() at
>> kernel/xenomai/nucleus/heap.c:332 that does this, with a junk pointer
>> dereference. So, heap->stat_link.next is not valid at the time of this
>> call, yet it's initialized by the call to inith() on line 319. I don't
>> know what would have changed that, unless it's a bad pointer elsewhere
>> that caused overwriting of this data. Any ideas where to go from here?
>>
> If the bug is reproducible, two things you can try:
> - enable CONFIG_XENO_OPT_DEBUG_QUEUES
> - enable the I-pipe tracer and panic freezes, you should get a trace
> when the bug happens.
>
Hi Gilles,

I finally got a bit more information. The crash occurred again today on
my testing hardware, so I installed a kernel with I-pipe trace and queue
debugging and tried to reproduce. I didn't get the same error, and the
kernel didn't oops, but I did get some interesting-looking information
in the log. It looks like something bad was happening with XDDP, but I
can't figure out what. Hopefully the attached log file will get through.

Thanks,
      --Doug Brunner