linux-kernel - [PATCH v8 07/16] sched/core: uclamp: Reset uclamp values on RESET_ON

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Message-Id: <20190402104153.25404-8-patrick.bellasi@arm.com>
Date:   Tue,  2 Apr 2019 11:41:43 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH v8 07/16] sched/core: 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@....com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 kernel/sched/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 68aed32e8ec7..bdebdabe9bc4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1070,6 +1070,17 @@ static void uclamp_fork(struct task_struct *p)
 
 	for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id)
 		p->uclamp[clamp_id].active = false;
+
+	if (likely(!p->sched_reset_on_fork))
+		return;
+
+	for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
+		unsigned int clamp_value = uclamp_none(clamp_id);
+
+		p->uclamp_req[clamp_id].user_defined = false;
+		p->uclamp_req[clamp_id].value = clamp_value;
+		p->uclamp_req[clamp_id].bucket_id = uclamp_bucket_id(clamp_value);
+	}
 }
 
 static void __init init_uclamp(void)
-- 
2.20.1