[tip:sched/core] sched/uclamp: Reset uclamp values on RESET_ON_FORK

[tip-bot for Patrick Bellasi]

Commit-ID:  a87498ace58e23b62a572dc7267579ede4c8495c
Gitweb:     https://git.kernel.org/tip/a87498ace58e23b62a572dc7267579ede4c8495c
Author:     Patrick Bellasi <patrick.bellasi@xxxxxxx>
AuthorDate: Fri, 21 Jun 2019 09:42:08 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 24 Jun 2019 19:23:47 +0200

sched/uclamp: Reset uclamp values on RESET_ON_FORK

A forked tasks gets the same clamp values of its parent however, when
the RESET_ON_FORK flag is set on parent, e.g. via:

   sys_sched_setattr()
      sched_setattr()
         __sched_setscheduler(attr::SCHED_FLAG_RESET_ON_FORK)

the new forked task is expected to start with all attributes reset to
default values.

Do that for utilization clamp values too by checking the reset request
from the existing uclamp_fork() call which already provides the required
initialization for other uclamp related bits.

Signed-off-by: Patrick Bellasi <patrick.bellasi@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Alessio Balsini <balsini@xxxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Joel Fernandes <joelaf@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Morten Rasmussen <morten.rasmussen@xxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Quentin Perret <quentin.perret@xxxxxxx>
Cc: Rafael J . Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Steve Muckle <smuckle@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Todd Kjos <tkjos@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20190621084217.8167-8-patrick.bellasi@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/sched/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e9a669266fa9..ecc304ab906f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1082,6 +1082,14 @@ static void uclamp_fork(struct task_struct *p)
 
 	for_each_clamp_id(clamp_id)
 		p->uclamp[clamp_id].active = false;
+
+	if (likely(!p->sched_reset_on_fork))
+		return;
+
+	for_each_clamp_id(clamp_id) {
+		uclamp_se_set(&p->uclamp_req[clamp_id],
+			      uclamp_none(clamp_id), false);
+	}
 }
 
 static void __init init_uclamp(void)