linux-kernel - [PATCH 7/7] sched-clock: Migrate to use new tick dependency mask model

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Message-Id: <1447424529-13671-8-git-send-email-fweisbec@gmail.com>
Date:	Fri, 13 Nov 2015 15:22:09 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Ingo Molnar <mingo@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Rik van Riel <riel@...hat.com>
Subject: [PATCH 7/7] sched-clock: Migrate to use new tick dependency mask model

Instead of checking sched_clock_stable from the nohz subsystem to verify
its tick dependency, migrate it to the new mask in order to include it
to the all-in-one check.

Cc: Christoph Lameter <cl@...ux.com>
Cc: Chris Metcalf <cmetcalf@...hip.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Luiz Capitulino <lcapitulino@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 kernel/sched/clock.c     |  5 +++++
 kernel/time/tick-sched.c | 26 ++++++--------------------
 2 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index c0a2051..1389e1a 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -61,6 +61,7 @@
 #include <linux/static_key.h>
 #include <linux/workqueue.h>
 #include <linux/compiler.h>
+#include <linux/tick.h>
 
 /*
  * Scheduler clock - returns current time in nanosec units.
@@ -89,6 +90,8 @@ static void __set_sched_clock_stable(void)
 {
 	if (!sched_clock_stable())
 		static_key_slow_inc(&__sched_clock_stable);
+
+	tick_nohz_clear_dep(TICK_CLOCK_UNSTABLE_BIT);
 }
 
 void set_sched_clock_stable(void)
@@ -108,6 +111,8 @@ static void __clear_sched_clock_stable(struct work_struct *work)
 	/* XXX worry about clock continuity */
 	if (sched_clock_stable())
 		static_key_slow_dec(&__sched_clock_stable);
+
+	tick_nohz_set_dep(TICK_CLOCK_UNSTABLE_BIT);
 }
 
 static DECLARE_WORK(sched_clock_work, __clear_sched_clock_stable);
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2a1ce82..bc419f84 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -174,8 +174,13 @@ static void trace_tick_dependency(unsigned long dep)
 		return;
 	}
 
-	if (dep & TICK_CLOCK_UNSTABLE_MASK)
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+	if (dep & TICK_CLOCK_UNSTABLE_MASK) {
 		trace_tick_stop(0, "unstable sched clock\n");
+		WARN_ONCE(tick_nohz_full_running,
+			  "NO_HZ FULL will not work with unstable sched clock");
+	}
+#endif
 }
 
 static bool can_stop_full_tick(struct tick_sched *ts)
@@ -202,25 +207,6 @@ static bool can_stop_full_tick(struct tick_sched *ts)
 		return false;
 	}
 
-#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
-	/*
-	 * sched_clock_tick() needs us?
-	 *
-	 * TODO: kick full dynticks CPUs when
-	 * sched_clock_stable is set.
-	 */
-	if (!sched_clock_stable()) {
-		trace_tick_stop(0, "unstable sched clock\n");
-		/*
-		 * Don't allow the user to think they can get
-		 * full NO_HZ with this machine.
-		 */
-		WARN_ONCE(tick_nohz_full_running,
-			  "NO_HZ FULL will not work with unstable sched clock");
-		return false;
-	}
-#endif
-
 	return true;
 }
 
-- 
2.5.3

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