[PATCH v3 2/8] sched/core: Propagate parent task's latency requirements to the child task

[Vincent Guittot]

From: Parth Shah <parth@xxxxxxxxxxxxx>

Clone parent task's latency_nice attribute to the forked child task.

Reset the latency_nice value to default value when the child task is
set to sched_reset_on_fork.

Also, initialize init_task.latency_nice value with DEFAULT_LATENCY_NICE
value

Signed-off-by: Parth Shah <parth@xxxxxxxxxxxxx>
[rebase]
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 init/init_task.c    | 1 +
 kernel/sched/core.c | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/init/init_task.c b/init/init_task.c
index 73cc8f03511a..225d11a39bc9 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -78,6 +78,7 @@ struct task_struct init_task
 	.prio		= MAX_PRIO - 20,
 	.static_prio	= MAX_PRIO - 20,
 	.normal_prio	= MAX_PRIO - 20,
+	.latency_nice	= DEFAULT_LATENCY_NICE,
 	.policy		= SCHED_NORMAL,
 	.cpus_ptr	= &init_task.cpus_mask,
 	.user_cpus_ptr	= NULL,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 603a80ec9b0e..3c5fb04f00e1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4511,6 +4511,9 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 	 */
 	p->prio = current->normal_prio;
 
+	/* Propagate the parent's latency requirements to the child as well */
+	p->latency_nice = current->latency_nice;
+
 	uclamp_fork(p);
 
 	/*
@@ -4527,6 +4530,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 		p->prio = p->normal_prio = p->static_prio;
 		set_load_weight(p, false);
 
+		p->latency_nice = DEFAULT_LATENCY_NICE;
 		/*
 		 * We don't need the reset flag anymore after the fork. It has
 		 * fulfilled its duty:
-- 
2.17.1