[PATCH 09/21] context_tracking: Take idle eqs entrypoints over RCU

Frederic Weisbecker
2022-05-19T15:00:13Z

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@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao<liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.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 | 15 +++++++++++++++
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 +
kernel/time/Kconfig | 6 ++++++
14 files changed, 53 insertions(+), 20 deletions(-)

diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst
index 794837eb519b..b95bda7755fa 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..01abadb2f993 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_IDLE
+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_IDLE */
+
#endif
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f9f75a3cfeb8..a7b7c459d5d4 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..26e67da7d90a 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -22,6 +22,21 @@
#include <linux/export.h>
#include <linux/kprobes.h>

+
+#ifdef CONFIG_CONTEXT_TRACKING_IDLE
+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);
+#endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
+
#ifdef CONFIG_CONTEXT_TRACKING_USER

#define CREATE_TRACE_POINTS
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 c05ca52cdf64..d471d22a5e21 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_IDLE
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 ff97264d8077..c2792b200958 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -668,7 +668,6 @@ void noinstr rcu_idle_enter(void)
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled());
rcu_eqs_enter(false);
}
-EXPORT_SYMBOL_GPL(rcu_idle_enter);

#ifdef CONFIG_NO_HZ_FULL

@@ -908,7 +907,6 @@ void noinstr rcu_idle_exit(void)
rcu_eqs_exit(false);
raw_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>
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 41f99bcfe9e6..a41753be1a2b 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -76,6 +76,12 @@ config TIME_KUNIT_TEST
config CONTEXT_TRACKING
bool

+config CONTEXT_TRACKING_IDLE
+ bool
+ select CONTEXT_TRACKING
+ help
+ Tracks idle state on behalf of RCU.
+
if GENERIC_CLOCKEVENTS
menu "Timers subsystem"

--
2.25.1