linux-kernel - [RFC 2/3] sched/idle: make cpu_idle_force

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Date:	Tue, 22 Sep 2015 16:34:21 -0400
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	riel@...hat.com, rafael.j.wysocki@...el.com, mingo@...nel.org
Subject: [RFC 2/3] sched/idle: make cpu_idle_force_poll per-cpu

In preparation to support setting idle polling behavior
at run-time, this commit makes the cpu_idle_force_poll
global counter a per-cpu data.

The new per-cpu data is actually a struct, and new
helper functions are added in order to maintain the
same semantics cpu_idle_force_poll used to have.

This change should not be visible to arch code calling
cpu_idle_poll_ctrl().

Signed-off-by: Luiz Capitulino <lcapitulino@...hat.com>
---
 kernel/sched/idle.c | 42 +++++++++++++++++++++++++++++++-----------
 1 file changed, 31 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 93d0657..3060977 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -24,29 +24,49 @@ void sched_idle_set_state(struct cpuidle_state *idle_state)
 	idle_set_state(this_rq(), idle_state);
 }
 
-static int __read_mostly cpu_idle_force_poll;
+struct idle_poll {
+	int force_poll;
+};
+
+static DEFINE_PER_CPU(struct idle_poll, idle_poll) = {
+	.force_poll = 0,
+};
+
+static bool this_cpu_idle_poll(void)
+{
+	return per_cpu(idle_poll, smp_processor_id()).force_poll > 0;
+}
+
+static void cpu_idle_poll_set_all(int v)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		per_cpu(idle_poll, cpu).force_poll = v;
+}
 
 void cpu_idle_poll_ctrl(bool enable)
 {
-	if (enable) {
-		cpu_idle_force_poll++;
-	} else {
-		cpu_idle_force_poll--;
-		WARN_ON_ONCE(cpu_idle_force_poll < 0);
+	int *p, cpu;
+
+	for_each_possible_cpu(cpu) {
+		p = &per_cpu(idle_poll, cpu).force_poll;
+		enable == true ? ++*p : --*p;
+		WARN_ON_ONCE(*p < 0);
 	}
 }
 
 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
 static int __init cpu_idle_poll_setup(char *__unused)
 {
-	cpu_idle_force_poll = 1;
+	cpu_idle_poll_set_all(1);
 	return 1;
 }
 __setup("nohlt", cpu_idle_poll_setup);
 
 static int __init cpu_idle_nopoll_setup(char *__unused)
 {
-	cpu_idle_force_poll = 0;
+	cpu_idle_poll_set_all(0);
 	return 1;
 }
 __setup("hlt", cpu_idle_nopoll_setup);
@@ -58,7 +78,7 @@ static inline void cpu_idle_poll(void)
 	trace_cpu_idle_rcuidle(0, smp_processor_id());
 	local_irq_enable();
 	while (!tif_need_resched() &&
-		(cpu_idle_force_poll || tick_check_broadcast_expired()))
+		(this_cpu_idle_poll() || tick_check_broadcast_expired()))
 		cpu_relax();
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 	rcu_idle_exit();
@@ -71,7 +91,7 @@ void __weak arch_cpu_idle_exit(void) { }
 void __weak arch_cpu_idle_dead(void) { }
 void __weak arch_cpu_idle(void)
 {
-	cpu_idle_force_poll = 1;
+	cpu_idle_poll_set_all(1);
 	local_irq_enable();
 }
 
@@ -242,7 +262,7 @@ static void cpu_idle_loop(void)
 			 * know that the IPI is going to arrive right
 			 * away
 			 */
-			if (cpu_idle_force_poll || tick_check_broadcast_expired())
+			if (this_cpu_idle_poll() || tick_check_broadcast_expired())
 				cpu_idle_poll();
 			else
 				cpuidle_idle_call();
-- 
2.1.0

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