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>

2 files changed, 4 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index ad7b93be5691..88215066efae 100644
--- 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 98345e45b059..928cd74cff0d 100644
--- 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;
         }