Hmmm.  IRQ4 is "PCI ExternalCommand Write"?  But I'm not using PCI.  Here is the output:

# ./irqloop
NULL ->unmask handler, IRQ 4, chip <NULL>
Test mode:    user-space task
Port type:    serial
Port address: 0x3f8
Port IRQ:     4

Received IRQs:     0
Acknowledged IRQs: 0
Xenomai: POSIX: destroyed thread c0f80320


Philippe Gerum wrote: 
Steven A. Falco wrote:
  
I am testing kernel 2.6.23 ARCH=powerpc with Xenomai 2.4-rc4.  The 
clocktest and cyclictest work perfectly with the uic/spinlock patches.  
However, the irqloop test fails with the Oops shown below.

    

Please try the patch below. It looks like the chip descriptor does not implement
any unmask handler, which seems odd. This patch should tell us a bit more about
this issue.