sched: fix wakeup preemption clock

Impact: sharpen the wakeup-granularity to always be against current scheduler time

It was possible to do the preemption check against an old time stamp.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index ad7b93b..8821506 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2266,6 +2266,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
 
        smp_wmb();
        rq = task_rq_lock(p, &flags);
+       update_rq_clock(rq);
        old_state = p->state;
        if (!(old_state & state))
                goto out;
@@ -2323,7 +2324,6 @@ out_activate:
                schedstat_inc(p, se.nr_wakeups_local);
        else
                schedstat_inc(p, se.nr_wakeups_remote);
-       update_rq_clock(rq);
        activate_task(rq, p, 1);
        success = 1;
 

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 98345e4..928cd74 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1345,12 +1345,11 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
 {
        struct task_struct *curr = rq->curr;
        struct sched_entity *se = &curr->se, *pse = &p->se;
+       struct cfs_rq *cfs_rq = task_cfs_rq(curr);
 
-       if (unlikely(rt_prio(p->prio))) {
-               struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+       update_curr(cfs_rq);
 
-               update_rq_clock(rq);
-               update_curr(cfs_rq);
+       if (unlikely(rt_prio(p->prio))) {
                resched_task(curr);
                return;
        }