[Xenomai] Oops while running "cat /proc/xenomai/stat"

[Stefan Roese <stefan.roese@gmail.com>]

Hi,

I'm currently developing an RTDM driver communicating with an FPGA
located on the LPB on an MPC5200 PowerPC. This driver already seems
to work quite well. But when I run my test application
communicating with the device driver, and I try to check the
Xenomai stat's, I get a kernel crash:

root@generic-powerpc:~# cat /proc/xenomai/stat 
[   43.722984] Oops: Kernel access of bad area, sig: 11 [#1]
[   43.728503] mpc5200-simple-platform
[   43.732057] Modules linked in: rt_fpga(O) rt_mpc52xx_lpbfifo(O)
[   43.738107] NIP: c00646a8 LR: c0098b84 CTR: c0098b34
[   43.743173] REGS: c7025b40 TRAP: 0300   Tainted: G           O  (3.5.3-00253-g4699145-dirty)
[   43.751776] MSR: 00001032 <ME,IR,DR,RI>  CR: 24424488  XER: 20000000
[   43.758279] DAR: 00000000, DSISR: 22000000
[   43.762454] TASK = c7b75360[1430] 'cat' THREAD: c7024000
GPR00: 00000000 c7025bf0 c7b75360 c7b1ca0c 00000002 02000007 00000000 00000031 
GPR08: c7ab0000 c7b1cc00 00000000 00000000 c0098b34 100a5a74 10017830 10006834 
GPR16: 10006770 10006774 c7b1cc00 00000000 00000002 c033d385 c03264ac 00000025 
GPR24: c0320000 00000001 00000002 c03b3460 00000000 00000000 c7a6ccc4 c7a6ccb4 
[   43.796697] Call Trace:
[   43.799189] [c7025bf0] [c004c540] 0xc004c540 (unreliable)
[   43.804698] [c7025c20] [c0098b84] 0xc0098b84
[   43.809051] [c7025c40] [c90e4588] 0xc90e4588
[   43.813406] [c7025c50] [c90d8114] 0xc90d8114
[   43.817758] [c7025c60] [c005e85c] 0xc005e85c
[   43.822113] [c7025ca0] [c005aef0] 0xc005aef0
[   43.826465] [c7025cc0] [c000d664] 0xc000d664
[   43.830819] [c7025cd0] [c000f710] 0xc000f710
[   43.835175] --- Exception: 501 at 0xc01b2614

This happens reproducible upon the "cat" command from the shell.

Looking at the NIP (c00646a8), the PPC is currently executing
xnsynch_flush().

Other proc files from the xenomai directory like "irq" don't cause
this crash. And accessing "stat" when this application is not
running also works fine:

root@generic-powerpc:~# cat /proc/xenomai/stat 
CPU  PID    MSW        CSW        PF    STAT       %CPU  NAME
  0  0      0          0          0     00500080  100.0  ROOT
  0  0      0          0          0     00000000    0.0  IRQ145: rtcan_mscan
  0  0      0          0          0     00000000    0.0  IRQ151: mpc52xx-lpbfifo
  0  0      0          0          0     00000000    0.0  IRQ194: mpc52xx-lpbfifo-rx
  0  0      0          17619      0     00000000    0.0  IRQ512: [timer]

Any idea what might go wrong here? 

Thanks,
Stefan