sched: Make sure task has correct sched_class after policy change

From the code in rt_mutex_setprio(), it is evident that the
intention is that task's with a RT 'prio' value as a consequence
of receiving a PI boost also have their 'sched_class' field set
to '&rt_sched_class'.

However, Peter noticed that the code in __setscheduler() could
result in this intention being frustrated. Fix it.

Reported-by: Peter Williams <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Mike Galbraith <[email protected]>
LKML-Reference: <1257880321.4108.457.camel@laptop>
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/sched.c b/kernel/sched.c
index ad37776cc39bb1df1e24fed63bd48f48509d9c96..43e61fa04dc7194b1cbef98712d9e93b1a687316 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6159,22 +6159,14 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio)
        BUG_ON(p->se.on_rq);
 
        p->policy = policy;
-       switch (p->policy) {
-       case SCHED_NORMAL:
-       case SCHED_BATCH:
-       case SCHED_IDLE:
-               p->sched_class = &fair_sched_class;
-               break;
-       case SCHED_FIFO:
-       case SCHED_RR:
-               p->sched_class = &rt_sched_class;
-               break;
-       }
-
        p->rt_priority = prio;
        p->normal_prio = normal_prio(p);
        /* we are holding p->pi_lock already */
        p->prio = rt_mutex_getprio(p);
+       if (rt_prio(p->prio))
+               p->sched_class = &rt_sched_class;
+       else
+               p->sched_class = &fair_sched_class;
        set_load_weight(p);
 }