linux-kernel - [PATCH 10/14] context_tracking: Check static key on context_tracking_enabled

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Date:   Wed, 16 Oct 2019 04:56:56 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yauheni Kaliuta <yauheni.kaliuta@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Pavel Machek <pavel@....cz>
Subject: [PATCH 10/14] context_tracking: Check static key on context_tracking_enabled_*cpu()

guest_enter() doesn't call context_tracking_enabled() before calling
context_tracking_enabled_this_cpu(). Therefore the guest code doesn't
benefit from the static key on the fast path.

Just make sure that context_tracking_enabled_*cpu() functions check
the static key by themselves to propagate the optimization.

Reported-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Yauheni Kaliuta <yauheni.kaliuta@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Rik van Riel <riel@...riel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Wanpeng Li <wanpengli@...cent.com>
Cc: Ingo Molnar <mingo@...nel.org>
---
 include/linux/context_tracking_state.h | 4 ++--
 include/linux/vtime.h                  | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 587717705727..e7fe6678b7ad 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -33,12 +33,12 @@ static inline bool context_tracking_enabled(void)
 
 static inline bool context_tracking_enabled_cpu(int cpu)
 {
-	return per_cpu(context_tracking.active, cpu);
+	return context_tracking_enabled() && per_cpu(context_tracking.active, cpu);
 }
 
 static inline bool context_tracking_enabled_this_cpu(void)
 {
-	return __this_cpu_read(context_tracking.active);
+	return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
 }
 
 static inline bool context_tracking_in_user(void)
diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index e2733bf33541..2cdeca062db3 100644
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -33,12 +33,12 @@ static inline bool vtime_accounting_enabled(void)
 
 static inline bool vtime_accounting_enabled_cpu(int cpu)
 {
-	return (vtime_accounting_enabled() && context_tracking_enabled_cpu(cpu));
+	return context_tracking_enabled_cpu(cpu);
 }
 
 static inline bool vtime_accounting_enabled_this_cpu(void)
 {
-	return (vtime_accounting_enabled() && context_tracking_enabled_this_cpu());
+	return context_tracking_enabled_this_cpu();
 }
 
 extern void vtime_task_switch_generic(struct task_struct *prev);
-- 
2.23.0