Message-Id: <20220503100051.2799723-11-frederic@kernel.org>
Date:   Tue,  3 May 2022 12:00:40 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Phil Auld <pauld@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu Liao <liaoyu15@...wei.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: [PATCH 10/21] context_tracking: Take idle eqs entrypoints over RCU

The RCU dynticks counter is going to be merged into the context tracking
subsystem. Start with moving the idle extended quiescent states
entrypoints to context tracking. For now those are dumb redirections to
existing RCU calls.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@...cinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@...y.com>
Cc: Joel Fernandes <joel@...lfernandes.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Nicolas Saenz Julienne <nsaenz@...nel.org>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@...wei.com>
Cc: Yu Liao<liaoyu15@...wei.com>
Cc: Phil Auld <pauld@...hat.com>
Cc: Paul Gortmaker<paul.gortmaker@...driver.com>
Cc: Alex Belits <abelits@...vell.com>
---
 Documentation/RCU/stallwarn.rst   |  4 ++--
 arch/arm/mach-imx/cpuidle-imx6q.c |  5 +++--
 drivers/acpi/processor_idle.c     |  5 +++--
 drivers/cpuidle/cpuidle.c         |  9 +++++----
 include/linux/context_tracking.h  |  8 ++++++++
 include/linux/rcupdate.h          |  2 +-
 kernel/context_tracking.c         | 12 ++++++++++++
 kernel/locking/lockdep.c          |  2 +-
 kernel/rcu/Kconfig                |  2 ++
 kernel/rcu/tree.c                 |  2 --
 kernel/rcu/update.c               |  2 +-
 kernel/sched/idle.c               | 10 +++++-----
 kernel/sched/sched.h              |  1 +
 13 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst
index 1d863b04727c..bdd52b40f307 100644
--- a/Documentation/RCU/stallwarn.rst
+++ b/Documentation/RCU/stallwarn.rst
@@ -97,8 +97,8 @@ warnings:
 	which will include additional debugging information.
 
 -	A low-level kernel issue that either fails to invoke one of the
-	variants of rcu_user_enter(), rcu_user_exit(), rcu_idle_enter(),
-	rcu_idle_exit(), rcu_irq_enter(), or rcu_irq_exit() on the one
+	variants of rcu_user_enter(), rcu_user_exit(), ct_idle_enter(),
+	ct_idle_exit(), rcu_irq_enter(), or rcu_irq_exit() on the one
 	hand, or that invokes one of them too many times on the other.
 	Historically, the most frequent issue has been an omission
 	of either irq_enter() or irq_exit(), which in turn invoke
diff --git a/arch/arm/mach-imx/cpuidle-imx6q.c b/arch/arm/mach-imx/cpuidle-imx6q.c
index 094337dc1bc7..d086cbae09c3 100644
--- a/arch/arm/mach-imx/cpuidle-imx6q.c
+++ b/arch/arm/mach-imx/cpuidle-imx6q.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2012 Freescale Semiconductor, Inc.
  */
 
+#include <linux/context_tracking.h>
 #include <linux/cpuidle.h>
 #include <linux/module.h>
 #include <asm/cpuidle.h>
@@ -24,9 +25,9 @@ static int imx6q_enter_wait(struct cpuidle_device *dev,
 		imx6_set_lpm(WAIT_UNCLOCKED);
 	raw_spin_unlock(&cpuidle_lock);
 
-	rcu_idle_enter();
+	ct_idle_enter();
 	cpu_do_idle();
-	rcu_idle_exit();
+	ct_idle_exit();
 
 	raw_spin_lock(&cpuidle_lock);
 	if (num_idle_cpus-- == num_online_cpus())
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 32b20efff5f8..935f4113d5f6 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -22,6 +22,7 @@
 #include <linux/cpu.h>
 #include <linux/minmax.h>
 #include <acpi/processor.h>
+#include <linux/context_tracking.h>
 
 /*
  * Include the apic definitions for x86 to have the APIC timer related defines
@@ -648,11 +649,11 @@ static int acpi_idle_enter_bm(struct cpuidle_driver *drv,
 		raw_spin_unlock(&c3_lock);
 	}
 
-	rcu_idle_enter();
+	ct_idle_enter();
 
 	acpi_idle_do_entry(cx);
 
-	rcu_idle_exit();
+	ct_idle_exit();
 
 	/* Re-enable bus master arbitration */
 	if (dis_bm) {
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index ef2ea1b12cd8..62dd956025f3 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -23,6 +23,7 @@
 #include <linux/suspend.h>
 #include <linux/tick.h>
 #include <linux/mmu_context.h>
+#include <linux/context_tracking.h>
 #include <trace/events/power.h>
 
 #include "cpuidle.h"
@@ -150,12 +151,12 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv,
 	 */
 	stop_critical_timings();
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_enter();
+		ct_idle_enter();
 	target_state->enter_s2idle(dev, drv, index);
 	if (WARN_ON_ONCE(!irqs_disabled()))
 		local_irq_disable();
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_exit();
+		ct_idle_exit();
 	tick_unfreeze();
 	start_critical_timings();
 
@@ -233,10 +234,10 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
 
 	stop_critical_timings();
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_enter();
+		ct_idle_enter();
 	entered_state = target_state->enter(dev, drv, index);
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_exit();
+		ct_idle_exit();
 	start_critical_timings();
 
 	sched_clock_idle_wakeup_event();
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index e35ae66b4794..27afb75f2650 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -119,4 +119,12 @@ extern void context_tracking_init(void);
 static inline void context_tracking_init(void) { }
 #endif /* CONFIG_CONTEXT_TRACKING_USER_FORCE */
 
+#ifdef CONFIG_CONTEXT_TRACKING
+extern void ct_idle_enter(void);
+extern void ct_idle_exit(void);
+#else
+static inline void ct_idle_enter(void) { }
+static inline void ct_idle_exit(void) { }
+#endif /* !CONFIG_CONTEXT_TRACKING */
+
 #endif
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 7f12daa4708b..d3b25e65f144 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -129,7 +129,7 @@ static inline void rcu_nocb_flush_deferred_wakeup(void) { }
  * @a: Code that RCU needs to pay attention to.
  *
  * RCU read-side critical sections are forbidden in the inner idle loop,
- * that is, between the rcu_idle_enter() and the rcu_idle_exit() -- RCU
+ * that is, between the ct_idle_enter() and the ct_idle_exit() -- RCU
  * will happily ignore any such read-side critical sections.  However,
  * things like powertop need tracepoints in the inner idle loop.
  *
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index da067a36b326..987f0b2a3962 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -251,3 +251,15 @@ void __init context_tracking_init(void)
 #endif
 
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_USER */
+
+noinstr void ct_idle_enter(void)
+{
+	rcu_idle_enter();
+}
+EXPORT_SYMBOL_GPL(ct_idle_enter);
+
+void ct_idle_exit(void)
+{
+	rcu_idle_exit();
+}
+EXPORT_SYMBOL_GPL(ct_idle_exit);
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index c06cab6546ed..5f0dfe37234b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -6546,7 +6546,7 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
 
 	/*
 	 * If a CPU is in the RCU-free window in idle (ie: in the section
-	 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
+	 * between ct_idle_enter() and ct_idle_exit(), then RCU
 	 * considers that CPU to be in an "extended quiescent state",
 	 * which means that RCU will be completely ignoring that CPU.
 	 * Therefore, rcu_read_lock() and friends have absolutely no
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 27aab870ae4c..85f3b884fa09 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -8,6 +8,8 @@ menu "RCU Subsystem"
 config TREE_RCU
 	bool
 	default y if SMP
+	# Dynticks-idle tracking
+	select CONTEXT_TRACKING
 	help
 	  This option selects the RCU implementation that is
 	  designed for very large SMP system with hundreds or
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2a6e7723fc4d..92a288668e7c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -664,7 +664,6 @@ noinstr void rcu_idle_enter(void)
 	lockdep_assert_irqs_disabled();
 	rcu_eqs_enter(false);
 }
-EXPORT_SYMBOL_GPL(rcu_idle_enter);
 
 #ifdef CONFIG_NO_HZ_FULL
 
@@ -912,7 +911,6 @@ void rcu_idle_exit(void)
 	rcu_eqs_exit(false);
 	local_irq_restore(flags);
 }
-EXPORT_SYMBOL_GPL(rcu_idle_exit);
 
 #ifdef CONFIG_NO_HZ_FULL
 /**
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 2e93acad1e31..738842c4886b 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -85,7 +85,7 @@ module_param(rcu_normal_after_boot, int, 0444);
  * and while lockdep is disabled.
  *
  * Note that if the CPU is in the idle loop from an RCU point of view (ie:
- * that we are in the section between rcu_idle_enter() and rcu_idle_exit())
+ * that we are in the section between ct_idle_enter() and ct_idle_exit())
  * then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an
  * rcu_read_lock().  The reason for this is that RCU ignores CPUs that are
  * in such a section, considering these as in extended quiescent state,
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 8f8b5020e76a..6de222b23b49 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -53,14 +53,14 @@ static noinline int __cpuidle cpu_idle_poll(void)
 {
 	trace_cpu_idle(0, smp_processor_id());
 	stop_critical_timings();
-	rcu_idle_enter();
+	ct_idle_enter();
 	local_irq_enable();
 
 	while (!tif_need_resched() &&
 	       (cpu_idle_force_poll || tick_check_broadcast_expired()))
 		cpu_relax();
 
-	rcu_idle_exit();
+	ct_idle_exit();
 	start_critical_timings();
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
 
@@ -98,12 +98,12 @@ void __cpuidle default_idle_call(void)
 		 *
 		 * Trace IRQs enable here, then switch off RCU, and have
 		 * arch_cpu_idle() use raw_local_irq_enable(). Note that
-		 * rcu_idle_enter() relies on lockdep IRQ state, so switch that
+		 * ct_idle_enter() relies on lockdep IRQ state, so switch that
 		 * last -- this is very similar to the entry code.
 		 */
 		trace_hardirqs_on_prepare();
 		lockdep_hardirqs_on_prepare(_THIS_IP_);
-		rcu_idle_enter();
+		ct_idle_enter();
 		lockdep_hardirqs_on(_THIS_IP_);
 
 		arch_cpu_idle();
@@ -116,7 +116,7 @@ void __cpuidle default_idle_call(void)
 		 */
 		raw_local_irq_disable();
 		lockdep_hardirqs_off(_THIS_IP_);
-		rcu_idle_exit();
+		ct_idle_exit();
 		lockdep_hardirqs_on(_THIS_IP_);
 		raw_local_irq_enable();
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 58263f90c559..f398f2bf05f4 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -27,6 +27,7 @@
 #include <linux/capability.h>
 #include <linux/cgroup_api.h>
 #include <linux/cgroup.h>
+#include <linux/context_tracking.h>
 #include <linux/cpufreq.h>
 #include <linux/cpumask_api.h>
 #include <linux/ctype.h>
-- 
2.25.1

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