sched: Fix task priority bug

83f9ac removed a call to effective_prio() in wake_up_new_task(), which
leads to tasks running at MAX_PRIO.

This is caused by the idle thread being set to MAX_PRIO before forking
off init. O(1) used that to make sure idle was always preempted, CFS
uses check_preempt_curr_idle() for that so we can savely remove this bit
of legacy code.

Reported-by: Mike Galbraith <efault@gmx.de>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259754383.4003.610.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 71eb062..3878f50 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3158,10 +3158,6 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
        deactivate_task(src_rq, p, 0);
        set_task_cpu(p, this_cpu);
        activate_task(this_rq, p, 0);
-       /*
-        * Note that idle threads have a prio of MAX_PRIO, for this test
-        * to be always true for them.
-        */
        check_preempt_curr(this_rq, p, 0);
 }
 
@@ -6992,7 +6988,6 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu)
        __sched_fork(idle);
        idle->se.exec_start = sched_clock();
 
-       idle->prio = idle->normal_prio = MAX_PRIO;
        cpumask_copy(&idle->cpus_allowed, cpumask_of(cpu));
        __set_task_cpu(idle, cpu);
 
@@ -7696,7 +7691,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
                spin_lock_irq(&rq->lock);
                update_rq_clock(rq);
                deactivate_task(rq, rq->idle, 0);
-               rq->idle->static_prio = MAX_PRIO;
                __setscheduler(rq, rq->idle, SCHED_NORMAL, 0);
                rq->idle->sched_class = &idle_sched_class;
                migrate_dead_tasks(cpu);