On Wed, 2012-12-05 at 17:05 +0100, Thomas Gleixner wrote: 

Dear RT Folks,

I'm pleased to announce the 3.6.9-rt21 release. 3.6.7-rt18, 3.6.8-rt19
and 3.6.9-rt20 are not announced updates to the respective 3.6.y
stable releases without any RT changes

Changes since 3.6.9-rt20:

   * Fix the PREEMPT_LAZY implementation on ARM

   * Fix the RCUTINY issues

   * Fix a long standing scheduler bug (See commit log of
     sched-enqueue-to-head.patch)

That last has an oversight buglet.

sched: add missing userspace->kernel struct sched_param.sched_priority inversion

Signed-off-by: Mike Galbraith <redacted>
---
 kernel/sched/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c

@@ -4624,7 +4624,7 @@ static int __sched_setscheduler(struct t
 	p->sched_reset_on_fork = reset_on_fork;
 
 	oldprio = p->prio;
-	if (oldprio == param->sched_priority)
+	if (oldprio == (MAX_RT_PRIO - 1) - param->sched_priority)
 		goto out;
 
 	on_rq = p->on_rq;