Hi,

Besides of the cpu load i also found out that with rt11 i can again wake up
usermode from a IRQF_NO_THREAD waiting on a waitqueue. So the steps outlined
in this mail http://www.spinics.net/lists/linux-rt-users/msg06834.html do not
seem to be neccessary anymore? Or does this create an error and than some high
load?

Try running with CONFIG_DEBUG_SPINLOCK_SLEEP and you would probably
see some errors...

If you have CONFIG_PREEMPT_RT_FULL set, then the __wake_up function of
the waitqueue runs into a spinlock. This spinlock will be converted to
a mutex since it is a regular spinlock, not a raw_spinlock. A
mutex-lock might sleep. Calling sleeping functions from hard-irq
context is illegal.

Kind regards,

Remy