LITMUS: don't let real-time tasks migrate by themselves

A proper real-time migration works as follows:
	1) transition to best-effort task
	2) migrate to target CPU
	3) update real-time parameters
	4) transition to real-time task

1 files changed, 3 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 00097dea89..7268034c88 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4536,10 +4536,11 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
         read_lock(&tasklist_lock);
 
         p = find_process_by_pid(pid);
-        if (!p) {
+        if (!p || is_realtime(p)) {
+                /* LITMUS tasks don't get to do this, transition to BE first */
                 read_unlock(&tasklist_lock);
                 mutex_unlock(&sched_hotcpu_mutex);
-                return -ESRCH;
+                return p ? -EPERM : -ESRCH;
         }
 
         /*