[Xenomai] rt_task_sleep returned -EPERM

[Wolfgang Netbal]

I am calling function rt_task_sleep and the returncode is -EPERM
In the xenomai api I found that this is returned from a task that cannot 
sleep
see below
http://xenomai.org/documentation/xenomai-2.6/html/api/group__task.html#gad5225e5fb8d583fbdfa5299f322b8366

I can exclude that I am in an interrupt or a non-realtime because all my 
tasks are shadowed.
But how can I have a scheduler locked ?

Kind regards
Wolfgang