sched: clean up idle task's mark_start restoring in init_idle()

The idle task's mark_start can get updated even without the CPU being
online. Hence the mark_start is restored when the CPU is coming online.

The idle task's mark_start is reset in init_idle()->__sched_fork()->
init_new_task_load(). The original mark_start is saved and restored
later. This can be avoided by moving init_new_task_load() to
wake_up_new_task(), which never gets called for an idle task.

We only care about idle task's ravg.mark_start and not initializing
the other fields of ravg struct will not have any side effects.

This clean up allows the subsequent patches to drop the rq->lock
while calling __sched_fork() in init_idle().

CRs-Fixed: 965873
Change-Id: I41de6d69944d7d44b9c4d11b2d97ad01bd8fe96d
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
[joonwoop@codeaurora.org: fixed a minor conflict in core.c.  omitted
 changes for CONFIG_SCHED_QHMP.]
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>

1 files changed, 1 insertions, 26 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f71e4882093c..4e5abc3bb294 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3648,16 +3648,6 @@ static int register_sched_callback(void)
  */
 core_initcall(register_sched_callback);
 
-static u64 orig_mark_start(struct task_struct *p)
-{
-	return p->ravg.mark_start;
-}
-
-static void restore_orig_mark_start(struct task_struct *p, u64 mark_start)
-{
-	p->ravg.mark_start = mark_start;
-}
-
 static inline int update_preferred_cluster(struct related_thread_group *grp,
 		struct task_struct *p, u32 old_load)
 {
@@ -3699,13 +3689,6 @@ static inline void set_window_start(struct rq *rq) {}
 
 static inline void migrate_sync_cpu(int cpu) {}
 
-static inline u64 orig_mark_start(struct task_struct *p) { return 0; }
-
-static inline void
-restore_orig_mark_start(struct task_struct *p, u64 mark_start)
-{
-}
-
 #endif	/* CONFIG_SCHED_HMP */
 
 #ifdef CONFIG_SMP
@@ -4912,7 +4895,6 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 	p->se.prev_sum_exec_runtime	= 0;
 	p->se.nr_migrations		= 0;
 	p->se.vruntime			= 0;
-	init_new_task_load(p);
 
 	INIT_LIST_HEAD(&p->se.group_node);
 
@@ -5182,6 +5164,7 @@ void wake_up_new_task(struct task_struct *p)
 	struct rq *rq;
 
 	raw_spin_lock_irqsave(&p->pi_lock, flags);
+	init_new_task_load(p);
 	/* Initialize new task's runnable average */
 	init_entity_runnable_average(&p->se);
 #ifdef CONFIG_SMP
@@ -7861,19 +7844,11 @@ void init_idle(struct task_struct *idle, int cpu)
 {
 	struct rq *rq = cpu_rq(cpu);
 	unsigned long flags;
-	u64 mark_start;
 
 	raw_spin_lock_irqsave(&idle->pi_lock, flags);
 	raw_spin_lock(&rq->lock);
 
-	mark_start = orig_mark_start(idle);
-
 	__sched_fork(0, idle);
-	/*
-	 * Restore idle thread's original mark_start as we rely on it being
-	 * correct for maintaining per-cpu counters, curr/prev_runnable_sum.
-	 */
-	restore_orig_mark_start(idle, mark_start);
 	idle->state = TASK_RUNNING;
 	idle->se.exec_start = sched_clock();