[Xenomai-help] page faults

[Jeff Weber <jweber@domain.hid>]

I need some help finding the cause for page faults in my RT application.
My app has a startup phase, where I can tolerate page faults, and a hard 
realtime phase, where page faults cannot be tolerated.  Trouble is, I 
continue to get page faults in the hard realtime phase.

The app encounters a page fault while writing to a heap buffer.  I've even 
added steps to clear the entire buffer in the startup phase, after 
mlockall(), to ensure each page is locked in place.  Here's a timeline of the 
fault:

static constructor runs and allocates buffer from heap
application main() runs
begin application startup phase
mlockall(MCL_CURRENT | MCL_FUTURE) runs and returns 0
entire buffer cleared
paranoid code even verifies buffer addr 0x81f4000 contents are 0
begin application hard realtime phase
time elapses ...
page fault copying stack addr 0xb645a2d1 to heap buffer addr 0x81f4000

The page fault is confirmed by the kernel debug message:
Xenomai: Switching mythread to secondary mode after exception #14 from 
user-space at 0x80fb8c5 (pid 3558)

as well as the delivery of SIGXCPU to my application (at my request).

How do I prevent this page fault?

Is this issue covered by the recent NOCOW activity?

	thanks,
	Jeff

my config:
CPU: VIA Nehemiah (i386)
ipipe version: 1.5-00
Xenomai: 2.2.4
Linux kernel: 2.6.17.14