| From | "Joel Fernandes (Google)" <> | Subject | [PATCH -tip 11/32] sched: Enqueue task into core queue only after vruntime is updated | Date | Tue, 17 Nov 2020 18:19:41 -0500 |
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A waking task may have its vruntime adjusted. However, the code right now puts it into the core queue without the adjustment. This means the core queue may have a task with incorrect vruntime, potentially a very long one. This may cause a task to get artificially boosted during picking.
Fix it by enqueuing into the core queue only after the class-specific enqueue callback has been called. This ensures that for CFS tasks, the updated vruntime value is used when enqueuing the task into the core rbtree.
Reviewed-by: Vineeth Pillai <viremana@linux.microsoft.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> --- kernel/sched/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 53af817740c0..6aa76de55ef2 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1753,9 +1753,6 @@ static inline void init_uclamp(void) { } static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { - if (sched_core_enabled(rq)) - sched_core_enqueue(rq, p); - if (!(flags & ENQUEUE_NOCLOCK)) update_rq_clock(rq); @@ -1766,6 +1763,9 @@ static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) uclamp_rq_inc(rq, p); p->sched_class->enqueue_task(rq, p, flags); + + if (sched_core_enabled(rq)) + sched_core_enqueue(rq, p); } static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) -- 2.29.2.299.gdc1121823c-goog
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