I am trying to do passive profiling of domains in xen on rhel5. kernel is 2.6.18-128.1.1.el5xen. I am using oprofile version 0.9.3 with the patched code for xenoprof.
When I start the daemon i get the following error but the daemon starts.
opcontrol --start-daemon --passive-domains=1,2,3,4,5 
/usr/bin/opcontrol: line 1275: echo: write error: Invalid argument
#this line write to /dev/oprofile/passive_domains file
/usr/bin/opcontrol: line 1118: echo: write error: Invalid argument
#this line writes to /dev/oprofile/backtrace_depth file
Using 2.6+ OProfile kernel interface.
Reading module info.
Using log file /var/lib/oprofile/samples/oprofiled.log
Daemon started.

if i try echo 1 > dev/oprofile/passive_domains, I still get the write error.

Even though the daemon starts the domains profiling does not happen since the file passive_domains is not written. Please help me fix this issue.

I have the exact same install on xen on ubuntu and that works perfectly fine.

Any help will be appreciated.