sched: group scheduler wakeup latency fix

group scheduler wakeup latency fix: when checking for preemption
we must check cross-group too, not just intra-group.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 5 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 48c69211888..5384a977c9a 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -796,7 +796,8 @@ static void yield_task_fair(struct rq *rq)
 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
 {
         struct task_struct *curr = rq->curr;
-        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+        struct cfs_rq *cfs_rq = task_cfs_rq(curr), *pcfs_rq;
+        struct sched_entity *se = &curr->se, *pse = &p->se;
 
         if (unlikely(rt_prio(p->prio))) {
                 update_rq_clock(rq);
@@ -804,11 +805,21 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
                 resched_task(curr);
                 return;
         }
-        if (is_same_group(curr, p)) {
-                s64 delta = curr->se.vruntime - p->se.vruntime;
 
-                if (delta > (s64)sysctl_sched_wakeup_granularity)
-                        resched_task(curr);
+        for_each_sched_entity(se) {
+                cfs_rq = cfs_rq_of(se);
+                pcfs_rq = cfs_rq_of(pse);
+
+                if (cfs_rq == pcfs_rq) {
+                        s64 delta = se->vruntime - pse->vruntime;
+
+                        if (delta > (s64)sysctl_sched_wakeup_granularity)
+                                resched_task(curr);
+                        break;
+                }
+#ifdef CONFIG_FAIR_GROUP_SCHED
+                pse = pse->parent;
+#endif
         }
 }