JACKerror: Cannot use real-time scheduling (RR/0)(22: Invalid argument)

JACKerror: JackClient::AcquireSelfRealTime error

this errors occurs every pd variants on my system: pd-vanliia 0.46-7, 0.45-4, pd-extended 0.43-4, but no errors with pd-l2ork 20151219(based on pd 0.42? i guess?).

my system:

ubuntu 14.04-3 LTS 64 bit

jackdmp 1.9.10

qjackctl 0.3.10