change kthread priority

Dear all: I have some questions about kthread: 1. can we change kthread priority through user mode program? 2. I found some functions that may be helpful. sched_getscheduler sched_setscheduler When I use them in user mode, the return value of sched_setscheduler  is fail. there is a thread talking about this, http://www.spinics.net/lists/linux-rt-users/msg06588.html What makes me confuse is "these 2 functions is used in user mode or kernel mode?" -- Regards, -- Regards, -- Regards,