[PATCH 00/21] rcu/context-tracking: Merge RCU eqs-dynticks counter to context tracking v2

[PATCH 00/21] rcu/context-tracking: Merge RCU eqs-dynticks counter to context tracking v2

[Frederic Weisbecker]

This mixes up the RCU dynticks counter and the context tracking state
updates into a single atomic instruction. This may serve several
purposes:

1) Improve CPU isolation with deferring some disturbances until sensitive
   userspace workload completes and goes to the kernel. This can take
   several forms, for example smp_call_function_housekeeping() or
   on_each_housekeeping_cpu() to enqueue and execute work on all
   housekeeping CPUs. Then an atomic operation on ct->state can defer
   the work on nohz_full CPUs until they run in kernel (or IPI them
   if they are in kernel mode), see this proposal by Peter:
   https://lore.kernel.org/all/20210929151723.162004989@infradead.org/#r

2) Unearth sysidle (https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=sysidle.2017.05.11a&id=fe5ac724d81a3c7803e60c2232718f212f3f38d4)
   This feature allowed to shutdown the tick on the last housekeeping
   CPU once the rest of the system is fully idle. We needed some proper
   fully ordered context tracking for that.

Inspired by Peterz: https://lore.kernel.org/all/20210929151723.162004989@infradead.org

Passed 100 hours of TREE01.

---
Changes since v1 after Paul, Nicolas and Peter's reviews:

* Rebased against latest rcu:dev

* Remove context_tracking_in_user()

* Tag rcu_idle_enter() as noinstr

* Add comments to explain why some RCU and context tracking functions can not
  be tagged as noinstr yet even though they should

* Add Acks from Paul

* Rename context_tracking_cpu_set() to ct_cpu_track_user()

* Some changelogs fixed

* Fix missing renames in cpuidle

* Add missing header comments for ct_irq_*()

* Add accessors for ->dynticks_nesting and ->dynticks_nmi_nesting

* Fix ->dynticks_nesting[_nmi] that were printed from the local ct
  instead of the remote one

* Only build rcu_irq_exit_check_preempt() when CONFIG_NO_HZ_FULL=y

* Remove static from rcu_preempt_deferred_qs() for all configs

* CONTEXT_* values now count from 0 to 4 instead of using bit flags,
  since all these states are mutually exclusive anyway.
  Therefore RCU_DYNTICKS_IDX now starts at 4 instead of 8.

* Keep the lowest bits of rcu_dynticks_snap() and expand a bit the
  printing size accordingly.

---
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	rcu/context-tracking-v2

HEAD: 0364ddb8830db4d4b78f7bfd9344e12d22e9cd32

Thanks,
	Frederic
---

Frederic Weisbecker (21):
      context_tracking: Remove unused context_tracking_in_user()
      rcu: Set rcu_idle_enter() as noinstr
      rcu: Add a note about noinstr VS unsafe eqs functions
      context_tracking: Add a note about noinstr VS unsafe context tracking functions
      context_tracking: Rename __context_tracking_enter/exit() to __ct_user_enter/exit()
      context_tracking: Rename context_tracking_user_enter/exit() to user_enter/exit_callable()
      context_tracking: Rename context_tracking_enter/exit() to ct_user_enter/exit()
      context_tracking: Rename context_tracking_cpu_set() to ct_cpu_track_user()
      context_tracking: Split user tracking Kconfig
      context_tracking: Take idle eqs entrypoints over RCU
      context_tracking: Take IRQ eqs entrypoints over RCU
      context_tracking: Take NMI eqs entrypoints over RCU
      rcu/context-tracking: Remove rcu_irq_enter/exit()
      rcu/context_tracking: Move dynticks counter to context tracking
      rcu/context_tracking: Move dynticks_nesting to context tracking
      rcu/context_tracking: Move dynticks_nmi_nesting to context tracking
      rcu/context-tracking: Move deferred nocb resched to context tracking
      rcu/context-tracking: Move RCU-dynticks internal functions to context_tracking
      rcu/context-tracking: Remove unused and/or unecessary middle functions
      context_tracking: Convert state to atomic_t
      rcu/context_tracking: Merge dynticks counter and context tracking states


 .../RCU/Design/Requirements/Requirements.rst       |  10 +-
 Documentation/RCU/stallwarn.rst                    |   6 +-
 .../time/context-tracking/arch-support.txt         |   6 +-
 arch/Kconfig                                       |   8 +-
 arch/arm/Kconfig                                   |   2 +-
 arch/arm/kernel/entry-common.S                     |   4 +-
 arch/arm/kernel/entry-header.S                     |  12 +-
 arch/arm/mach-imx/cpuidle-imx6q.c                  |   5 +-
 arch/arm64/Kconfig                                 |   2 +-
 arch/arm64/kernel/entry-common.c                   |  14 +-
 arch/csky/Kconfig                                  |   2 +-
 arch/csky/kernel/entry.S                           |   8 +-
 arch/mips/Kconfig                                  |   2 +-
 arch/powerpc/Kconfig                               |   2 +-
 arch/powerpc/include/asm/context_tracking.h        |   2 +-
 arch/riscv/Kconfig                                 |   2 +-
 arch/riscv/kernel/entry.S                          |  12 +-
 arch/sparc/Kconfig                                 |   2 +-
 arch/sparc/kernel/rtrap_64.S                       |   2 +-
 arch/x86/Kconfig                                   |   4 +-
 arch/x86/mm/fault.c                                |   2 +-
 drivers/acpi/processor_idle.c                      |   5 +-
 drivers/cpuidle/cpuidle-psci.c                     |   8 +-
 drivers/cpuidle/cpuidle-riscv-sbi.c                |   8 +-
 drivers/cpuidle/cpuidle.c                          |   9 +-
 include/linux/context_tracking.h                   |  89 ++--
 include/linux/context_tracking_irq.h               |  21 +
 include/linux/context_tracking_state.h             | 103 +++-
 include/linux/entry-common.h                       |  10 +-
 include/linux/hardirq.h                            |  12 +-
 include/linux/rcupdate.h                           |  15 +-
 include/linux/rcutiny.h                            |   6 -
 include/linux/rcutree.h                            |  15 +-
 include/linux/tracepoint.h                         |   4 +-
 init/Kconfig                                       |   4 +-
 kernel/context_tracking.c                          | 556 +++++++++++++++++++--
 kernel/cpu_pm.c                                    |   8 +-
 kernel/entry/common.c                              |  16 +-
 kernel/extable.c                                   |   4 +-
 kernel/locking/lockdep.c                           |   2 +-
 kernel/rcu/Kconfig                                 |   2 +
 kernel/rcu/rcu.h                                   |   4 -
 kernel/rcu/tree.c                                  | 476 +-----------------
 kernel/rcu/tree.h                                  |   8 -
 kernel/rcu/tree_exp.h                              |   2 +-
 kernel/rcu/tree_plugin.h                           |  38 +-
 kernel/rcu/tree_stall.h                            |   8 +-
 kernel/rcu/update.c                                |   2 +-
 kernel/sched/core.c                                |   2 +-
 kernel/sched/idle.c                                |  10 +-
 kernel/sched/sched.h                               |   1 +
 kernel/softirq.c                                   |   4 +-
 kernel/time/Kconfig                                |  22 +-
 kernel/time/tick-sched.c                           |   2 +-
 kernel/trace/trace.c                               |   8 +-
 55 files changed, 845 insertions(+), 748 deletions(-)

[PATCH 01/21] context_tracking: Remove unused context_tracking_in_user()

[Frederic Weisbecker]

This function is not used and CT_WARN_ON() coupled with ct_state() is
the preferred way to assert context tracking state values.

Reported-by: Nicolas Saenz Julienne <nsaenz@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>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 include/linux/context_tracking_state.h | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 65a60d3313b0..02be3ac2040d 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -41,12 +41,7 @@ static inline bool context_tracking_enabled_this_cpu(void)
 	return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
 }
 
-static __always_inline bool context_tracking_in_user(void)
-{
-	return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
-}
 #else
-static inline bool context_tracking_in_user(void) { return false; }
 static inline bool context_tracking_enabled(void) { return false; }
 static inline bool context_tracking_enabled_cpu(int cpu) { return false; }
 static inline bool context_tracking_enabled_this_cpu(void) { return false; }
-- 
2.25.1

[PATCH 02/21] rcu: Set rcu_idle_enter() as noinstr

[Frederic Weisbecker]

This function enters into RCU idle mode, make sure that illegal uses of
RCU are spotted there by objtools.

Reported-by: Peter Zijlstra <peterz@infradead.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>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5c587e00811c..a5da4b87afde 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -659,7 +659,7 @@ static noinstr void rcu_eqs_enter(bool user)
  * If you add or remove a call to rcu_idle_enter(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
  */
-void rcu_idle_enter(void)
+noinstr void rcu_idle_enter(void)
 {
 	lockdep_assert_irqs_disabled();
 	rcu_eqs_enter(false);
-- 
2.25.1

[PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Frederic Weisbecker]

Some RCU functions enter or exit into/from RCU idle mode while using
trace-able and lockdep-aware IRQs (un-)masking. This could be easily
solved with using raw versions of local_irq_*() but we would then
lose some precious debugging informations.

Another possible way to solve this may consist in using rude RCU-tasks
in lockdep and irqsoff tracing.

In any case and until this get solved, those RCU functions can't get
tagged as noinstr even though they should.

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>
---
 kernel/rcu/tree.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a5da4b87afde..2a6e7723fc4d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -838,6 +838,10 @@ void rcu_irq_exit_check_preempt(void)
  *
  * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_restore() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
  */
 void rcu_irq_exit_irqson(void)
 {
@@ -895,6 +899,10 @@ static void noinstr rcu_eqs_exit(bool user)
  *
  * If you add or remove a call to rcu_idle_exit(), be sure to test with
  * CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_save() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
  */
 void rcu_idle_exit(void)
 {
@@ -1076,6 +1084,10 @@ noinstr void rcu_irq_enter(void)
  *
  * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_save() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
  */
 void rcu_irq_enter_irqson(void)
 {
-- 
2.25.1

[PATCH 04/21] context_tracking: Add a note about noinstr VS unsafe context tracking functions

[Frederic Weisbecker]

Some context tracking functions enter or exit into/from RCU idle mode
while using trace-able and lockdep-aware IRQs (un-)masking. This could
be easily solved with using raw versions of local_irq_*() but we would
then lose some precious debugging informations.

Another possible way to solve this may consist in using rude RCU-tasks
in lockdep and irqsoff tracing.

In any case and until this get solved, those functions can't get
tagged as noinstr even though they should.

Reported-by: Peter Zijlstra <peterz@infradead.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>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/context_tracking.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 36a98c48aedc..1f44b0461d14 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -103,6 +103,11 @@ void noinstr __context_tracking_enter(enum ctx_state state)
 }
 EXPORT_SYMBOL_GPL(__context_tracking_enter);
 
+/*
+ * FIXME: This function should be noinstr but the below local_irq_restore() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep. This
+ * must be fixed first.
+ */
 void context_tracking_enter(enum ctx_state state)
 {
 	unsigned long flags;
@@ -125,6 +130,10 @@ void context_tracking_enter(enum ctx_state state)
 NOKPROBE_SYMBOL(context_tracking_enter);
 EXPORT_SYMBOL_GPL(context_tracking_enter);
 
+/*
+ * FIXME: This function should be noinstr but it unsafely calls local_irq_restore(),
+ * involving illegal RCU uses through tracing and lockdep. This must be fixed first.
+ */
 void context_tracking_user_enter(void)
 {
 	user_enter();
@@ -168,6 +177,11 @@ void noinstr __context_tracking_exit(enum ctx_state state)
 }
 EXPORT_SYMBOL_GPL(__context_tracking_exit);
 
+/*
+ * FIXME: This function should be noinstr but the below local_irq_save() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep. This
+ * must be fixed first.
+ */
 void context_tracking_exit(enum ctx_state state)
 {
 	unsigned long flags;
@@ -182,6 +196,10 @@ void context_tracking_exit(enum ctx_state state)
 NOKPROBE_SYMBOL(context_tracking_exit);
 EXPORT_SYMBOL_GPL(context_tracking_exit);
 
+/*
+ * FIXME: This function should be noinstr but it unsafely calls local_irq_save(),
+ * involving illegal RCU uses through tracing and lockdep. This must be fixed first.
+ */
 void context_tracking_user_exit(void)
 {
 	user_exit();
-- 
2.25.1

[PATCH 05/21] context_tracking: Rename __context_tracking_enter/exit() to __ct_user_enter/exit()

[Frederic Weisbecker]

The context tracking namespace is going to expand and some new functions
will require even longer names. Start shrinking the context_tracking
prefix to "ct" as is already the case for some existing macros, this
will make the introduction of new functions easier.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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>
---
 include/linux/context_tracking.h | 12 ++++++------
 kernel/context_tracking.c        | 20 ++++++++++----------
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 7a14807c9d1a..773035124bad 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -14,8 +14,8 @@
 extern void context_tracking_cpu_set(int cpu);
 
 /* Called with interrupts disabled.  */
-extern void __context_tracking_enter(enum ctx_state state);
-extern void __context_tracking_exit(enum ctx_state state);
+extern void __ct_user_enter(enum ctx_state state);
+extern void __ct_user_exit(enum ctx_state state);
 
 extern void context_tracking_enter(enum ctx_state state);
 extern void context_tracking_exit(enum ctx_state state);
@@ -38,13 +38,13 @@ static inline void user_exit(void)
 static __always_inline void user_enter_irqoff(void)
 {
 	if (context_tracking_enabled())
-		__context_tracking_enter(CONTEXT_USER);
+		__ct_user_enter(CONTEXT_USER);
 
 }
 static __always_inline void user_exit_irqoff(void)
 {
 	if (context_tracking_enabled())
-		__context_tracking_exit(CONTEXT_USER);
+		__ct_user_exit(CONTEXT_USER);
 }
 
 static inline enum ctx_state exception_enter(void)
@@ -74,7 +74,7 @@ static inline void exception_exit(enum ctx_state prev_ctx)
 static __always_inline bool context_tracking_guest_enter(void)
 {
 	if (context_tracking_enabled())
-		__context_tracking_enter(CONTEXT_GUEST);
+		__ct_user_enter(CONTEXT_GUEST);
 
 	return context_tracking_enabled_this_cpu();
 }
@@ -82,7 +82,7 @@ static __always_inline bool context_tracking_guest_enter(void)
 static __always_inline void context_tracking_guest_exit(void)
 {
 	if (context_tracking_enabled())
-		__context_tracking_exit(CONTEXT_GUEST);
+		__ct_user_exit(CONTEXT_GUEST);
 }
 
 /**
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 1f44b0461d14..554c2c9587eb 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -51,15 +51,15 @@ static __always_inline void context_tracking_recursion_exit(void)
 }
 
 /**
- * context_tracking_enter - Inform the context tracking that the CPU is going
- *                          enter user or guest space mode.
+ * __ct_user_enter - Inform the context tracking that the CPU is going
+ *		     to enter user or guest space mode.
  *
  * This function must be called right before we switch from the kernel
  * to user or guest space, when it's guaranteed the remaining kernel
  * instructions to execute won't use any RCU read side critical section
  * because this function sets RCU in extended quiescent state.
  */
-void noinstr __context_tracking_enter(enum ctx_state state)
+void noinstr __ct_user_enter(enum ctx_state state)
 {
 	/* Kernel threads aren't supposed to go to userspace */
 	WARN_ON_ONCE(!current->mm);
@@ -101,7 +101,7 @@ void noinstr __context_tracking_enter(enum ctx_state state)
 	}
 	context_tracking_recursion_exit();
 }
-EXPORT_SYMBOL_GPL(__context_tracking_enter);
+EXPORT_SYMBOL_GPL(__ct_user_enter);
 
 /*
  * FIXME: This function should be noinstr but the below local_irq_restore() is
@@ -124,7 +124,7 @@ void context_tracking_enter(enum ctx_state state)
 		return;
 
 	local_irq_save(flags);
-	__context_tracking_enter(state);
+	__ct_user_enter(state);
 	local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(context_tracking_enter);
@@ -141,8 +141,8 @@ void context_tracking_user_enter(void)
 NOKPROBE_SYMBOL(context_tracking_user_enter);
 
 /**
- * context_tracking_exit - Inform the context tracking that the CPU is
- *                         exiting user or guest mode and entering the kernel.
+ * __ct_user_exit - Inform the context tracking that the CPU is
+ * 		    exiting user or guest mode and entering the kernel.
  *
  * This function must be called after we entered the kernel from user or
  * guest space before any use of RCU read side critical section. This
@@ -152,7 +152,7 @@ NOKPROBE_SYMBOL(context_tracking_user_enter);
  * This call supports re-entrancy. This way it can be called from any exception
  * handler without needing to know if we came from userspace or not.
  */
-void noinstr __context_tracking_exit(enum ctx_state state)
+void noinstr __ct_user_exit(enum ctx_state state)
 {
 	if (!context_tracking_recursion_enter())
 		return;
@@ -175,7 +175,7 @@ void noinstr __context_tracking_exit(enum ctx_state state)
 	}
 	context_tracking_recursion_exit();
 }
-EXPORT_SYMBOL_GPL(__context_tracking_exit);
+EXPORT_SYMBOL_GPL(__ct_user_exit);
 
 /*
  * FIXME: This function should be noinstr but the below local_irq_save() is
@@ -190,7 +190,7 @@ void context_tracking_exit(enum ctx_state state)
 		return;
 
 	local_irq_save(flags);
-	__context_tracking_exit(state);
+	__ct_user_exit(state);
 	local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(context_tracking_exit);
-- 
2.25.1

[PATCH 06/21] context_tracking: Rename context_tracking_user_enter/exit() to user_enter/exit_callable()

[Frederic Weisbecker]

context_tracking_user_enter() and context_tracking_user_exit() are
ASM callable versions of user_enter() and user_exit() for architectures
that didn't manage to check the context tracking static key from ASM.
Change those function names to better reflect their purpose.

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>
---
 arch/arm/kernel/entry-header.S   |  8 ++++----
 arch/csky/kernel/entry.S         |  4 ++--
 arch/riscv/kernel/entry.S        |  6 +++---
 include/linux/context_tracking.h |  4 ++--
 kernel/context_tracking.c        | 20 ++++++++++++++------
 5 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 9a1dc142f782..0c14dcc43e58 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -370,10 +370,10 @@ ALT_UP_B(.L1_\@)
 #ifdef CONFIG_CONTEXT_TRACKING
 	.if	\save
 	stmdb   sp!, {r0-r3, ip, lr}
-	bl	context_tracking_user_exit
+	bl	user_exit_callable
 	ldmia	sp!, {r0-r3, ip, lr}
 	.else
-	bl	context_tracking_user_exit
+	bl	user_exit_callable
 	.endif
 #endif
 	.endm
@@ -382,10 +382,10 @@ ALT_UP_B(.L1_\@)
 #ifdef CONFIG_CONTEXT_TRACKING
 	.if	\save
 	stmdb   sp!, {r0-r3, ip, lr}
-	bl	context_tracking_user_enter
+	bl	user_enter_callable
 	ldmia	sp!, {r0-r3, ip, lr}
 	.else
-	bl	context_tracking_user_enter
+	bl	user_enter_callable
 	.endif
 #endif
 	.endm
diff --git a/arch/csky/kernel/entry.S b/arch/csky/kernel/entry.S
index a4ababf25e24..bc734d17c16f 100644
--- a/arch/csky/kernel/entry.S
+++ b/arch/csky/kernel/entry.S
@@ -23,7 +23,7 @@
 	mfcr	a0, epsr
 	btsti	a0, 31
 	bt	1f
-	jbsr	context_tracking_user_exit
+	jbsr	user_exit_callable
 	ldw	a0, (sp, LSAVE_A0)
 	ldw	a1, (sp, LSAVE_A1)
 	ldw	a2, (sp, LSAVE_A2)
@@ -160,7 +160,7 @@ ret_from_exception:
 	cmpnei	r10, 0
 	bt	exit_work
 #ifdef CONFIG_CONTEXT_TRACKING
-	jbsr	context_tracking_user_enter
+	jbsr	user_enter_callable
 #endif
 1:
 #ifdef CONFIG_PREEMPTION
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index c8b9ce274b9a..ecd132af2edf 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -112,11 +112,11 @@ _save_context:
 #endif
 
 #ifdef CONFIG_CONTEXT_TRACKING
-	/* If previous state is in user mode, call context_tracking_user_exit. */
+	/* If previous state is in user mode, call user_exit_callable(). */
 	li   a0, SR_PP
 	and a0, s1, a0
 	bnez a0, skip_context_tracking
-	call context_tracking_user_exit
+	call user_exit_callable
 skip_context_tracking:
 #endif
 
@@ -256,7 +256,7 @@ resume_userspace:
 	bnez s1, work_pending
 
 #ifdef CONFIG_CONTEXT_TRACKING
-	call context_tracking_user_enter
+	call user_enter_callable
 #endif
 
 	/* Save unwound kernel stack pointer in thread_info */
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 773035124bad..69532cd18f72 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -19,8 +19,8 @@ extern void __ct_user_exit(enum ctx_state state);
 
 extern void context_tracking_enter(enum ctx_state state);
 extern void context_tracking_exit(enum ctx_state state);
-extern void context_tracking_user_enter(void);
-extern void context_tracking_user_exit(void);
+extern void user_enter_callable(void);
+extern void user_exit_callable(void);
 
 static inline void user_enter(void)
 {
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 554c2c9587eb..e4e7aad6c2bc 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -130,15 +130,19 @@ void context_tracking_enter(enum ctx_state state)
 NOKPROBE_SYMBOL(context_tracking_enter);
 EXPORT_SYMBOL_GPL(context_tracking_enter);
 
-/*
+/**
+ * user_enter_callable() - Unfortunate ASM callable version of user_enter() for
+ * 			   archs that didn't manage to check the context tracking
+ * 			   static key from low level code.
+ *
  * FIXME: This function should be noinstr but it unsafely calls local_irq_restore(),
  * involving illegal RCU uses through tracing and lockdep. This must be fixed first.
  */
-void context_tracking_user_enter(void)
+void user_enter_callable(void)
 {
 	user_enter();
 }
-NOKPROBE_SYMBOL(context_tracking_user_enter);
+NOKPROBE_SYMBOL(user_enter_callable);
 
 /**
  * __ct_user_exit - Inform the context tracking that the CPU is
@@ -196,15 +200,19 @@ void context_tracking_exit(enum ctx_state state)
 NOKPROBE_SYMBOL(context_tracking_exit);
 EXPORT_SYMBOL_GPL(context_tracking_exit);
 
-/*
+/**
+ * user_exit_callable() - Unfortunate ASM callable version of user_exit() for
+ * 			  archs that didn't manage to check the context tracking
+ * 			  static key from low level code.
+ *
  * FIXME: This function should be noinstr but it unsafely calls local_irq_save(),
  * involving illegal RCU uses through tracing and lockdep. This must be fixed first.
  */
-void context_tracking_user_exit(void)
+void user_exit_callable(void)
 {
 	user_exit();
 }
-NOKPROBE_SYMBOL(context_tracking_user_exit);
+NOKPROBE_SYMBOL(user_exit_callable);
 
 void __init context_tracking_cpu_set(int cpu)
 {
-- 
2.25.1

[PATCH 07/21] context_tracking: Rename context_tracking_enter/exit() to ct_user_enter/exit()

[Frederic Weisbecker]

context_tracking_enter() and context_tracking_exit() have confusing
names that don't explain the fact they are referring to user/guest state.

Use more self-explanatory names and shrink to the new context tracking
prefix instead.

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>
---
 include/linux/context_tracking.h | 13 +++++++------
 kernel/context_tracking.c        | 12 ++++++------
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 69532cd18f72..7a5f04ae1758 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -17,21 +17,22 @@ extern void context_tracking_cpu_set(int cpu);
 extern void __ct_user_enter(enum ctx_state state);
 extern void __ct_user_exit(enum ctx_state state);
 
-extern void context_tracking_enter(enum ctx_state state);
-extern void context_tracking_exit(enum ctx_state state);
+extern void ct_user_enter(enum ctx_state state);
+extern void ct_user_exit(enum ctx_state state);
+
 extern void user_enter_callable(void);
 extern void user_exit_callable(void);
 
 static inline void user_enter(void)
 {
 	if (context_tracking_enabled())
-		context_tracking_enter(CONTEXT_USER);
+		ct_user_enter(CONTEXT_USER);
 
 }
 static inline void user_exit(void)
 {
 	if (context_tracking_enabled())
-		context_tracking_exit(CONTEXT_USER);
+		ct_user_exit(CONTEXT_USER);
 }
 
 /* Called with interrupts disabled.  */
@@ -57,7 +58,7 @@ static inline enum ctx_state exception_enter(void)
 
 	prev_ctx = this_cpu_read(context_tracking.state);
 	if (prev_ctx != CONTEXT_KERNEL)
-		context_tracking_exit(prev_ctx);
+		ct_user_exit(prev_ctx);
 
 	return prev_ctx;
 }
@@ -67,7 +68,7 @@ static inline void exception_exit(enum ctx_state prev_ctx)
 	if (!IS_ENABLED(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK) &&
 	    context_tracking_enabled()) {
 		if (prev_ctx != CONTEXT_KERNEL)
-			context_tracking_enter(prev_ctx);
+			ct_user_enter(prev_ctx);
 	}
 }
 
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index e4e7aad6c2bc..bfbc5d846a62 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -108,7 +108,7 @@ EXPORT_SYMBOL_GPL(__ct_user_enter);
  * unsafe because it involves illegal RCU uses through tracing and lockdep. This
  * must be fixed first.
  */
-void context_tracking_enter(enum ctx_state state)
+void ct_user_enter(enum ctx_state state)
 {
 	unsigned long flags;
 
@@ -127,8 +127,8 @@ void context_tracking_enter(enum ctx_state state)
 	__ct_user_enter(state);
 	local_irq_restore(flags);
 }
-NOKPROBE_SYMBOL(context_tracking_enter);
-EXPORT_SYMBOL_GPL(context_tracking_enter);
+NOKPROBE_SYMBOL(ct_user_enter);
+EXPORT_SYMBOL_GPL(ct_user_enter);
 
 /**
  * user_enter_callable() - Unfortunate ASM callable version of user_enter() for
@@ -186,7 +186,7 @@ EXPORT_SYMBOL_GPL(__ct_user_exit);
  * unsafe because it involves illegal RCU uses through tracing and lockdep. This
  * must be fixed first.
  */
-void context_tracking_exit(enum ctx_state state)
+void ct_user_exit(enum ctx_state state)
 {
 	unsigned long flags;
 
@@ -197,8 +197,8 @@ void context_tracking_exit(enum ctx_state state)
 	__ct_user_exit(state);
 	local_irq_restore(flags);
 }
-NOKPROBE_SYMBOL(context_tracking_exit);
-EXPORT_SYMBOL_GPL(context_tracking_exit);
+NOKPROBE_SYMBOL(ct_user_exit);
+EXPORT_SYMBOL_GPL(ct_user_exit);
 
 /**
  * user_exit_callable() - Unfortunate ASM callable version of user_exit() for
-- 
2.25.1

[PATCH 08/21] context_tracking: Rename context_tracking_cpu_set() to ct_cpu_track_user()

[Frederic Weisbecker]

context_tracking_cpu_set() is called in order to tell a CPU to track
user/kernel transitions. Since context tracking is going to expand in
to also track transitions from/to idle/IRQ/NMIs, the scope
of this function name becomes too broad and needs to be made more
specific. Also shorten the prefix to align with the new namespace.

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>
---
 include/linux/context_tracking.h | 2 +-
 kernel/context_tracking.c        | 4 ++--
 kernel/time/tick-sched.c         | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 7a5f04ae1758..63259fece7c7 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -11,7 +11,7 @@
 
 
 #ifdef CONFIG_CONTEXT_TRACKING
-extern void context_tracking_cpu_set(int cpu);
+extern void ct_cpu_track_user(int cpu);
 
 /* Called with interrupts disabled.  */
 extern void __ct_user_enter(enum ctx_state state);
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index bfbc5d846a62..f48eaad314ba 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -214,7 +214,7 @@ void user_exit_callable(void)
 }
 NOKPROBE_SYMBOL(user_exit_callable);
 
-void __init context_tracking_cpu_set(int cpu)
+void __init ct_cpu_track_user(int cpu)
 {
 	static __initdata bool initialized = false;
 
@@ -244,6 +244,6 @@ void __init context_tracking_init(void)
 	int cpu;
 
 	for_each_possible_cpu(cpu)
-		context_tracking_cpu_set(cpu);
+		ct_cpu_track_user(cpu);
 }
 #endif
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2d76c91b85de..06709885c590 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -571,7 +571,7 @@ void __init tick_nohz_init(void)
 	}
 
 	for_each_cpu(cpu, tick_nohz_full_mask)
-		context_tracking_cpu_set(cpu);
+		ct_cpu_track_user(cpu);
 
 	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
 					"kernel/nohz:predown", NULL,
-- 
2.25.1

[PATCH 09/21] context_tracking: Split user tracking Kconfig

[Frederic Weisbecker]

Context tracking is going to be used not only to track user transitions
but also idle/IRQs/NMIs. The user tracking part will then become a
separate feature. Prepare Kconfig for that.

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>
---
 .../time/context-tracking/arch-support.txt    |  6 ++---
 arch/Kconfig                                  |  4 ++--
 arch/arm/Kconfig                              |  2 +-
 arch/arm/kernel/entry-common.S                |  4 ++--
 arch/arm/kernel/entry-header.S                |  4 ++--
 arch/arm64/Kconfig                            |  2 +-
 arch/csky/Kconfig                             |  2 +-
 arch/csky/kernel/entry.S                      |  4 ++--
 arch/mips/Kconfig                             |  2 +-
 arch/powerpc/Kconfig                          |  2 +-
 arch/powerpc/include/asm/context_tracking.h   |  2 +-
 arch/riscv/Kconfig                            |  2 +-
 arch/riscv/kernel/entry.S                     |  6 ++---
 arch/sparc/Kconfig                            |  2 +-
 arch/sparc/kernel/rtrap_64.S                  |  2 +-
 arch/x86/Kconfig                              |  4 ++--
 include/linux/context_tracking.h              | 12 +++++-----
 include/linux/context_tracking_state.h        |  4 ++--
 init/Kconfig                                  |  4 ++--
 kernel/context_tracking.c                     |  6 ++++-
 kernel/sched/core.c                           |  2 +-
 kernel/time/Kconfig                           | 22 +++++++++++--------
 22 files changed, 54 insertions(+), 46 deletions(-)

diff --git a/Documentation/features/time/context-tracking/arch-support.txt b/Documentation/features/time/context-tracking/arch-support.txt
index bb1c1801553e..59ec30c84541 100644
--- a/Documentation/features/time/context-tracking/arch-support.txt
+++ b/Documentation/features/time/context-tracking/arch-support.txt
@@ -1,7 +1,7 @@
 #
-# Feature name:          context-tracking
-#         Kconfig:       HAVE_CONTEXT_TRACKING
-#         description:   arch supports context tracking for NO_HZ_FULL
+# Feature name:          user-context-tracking
+#         Kconfig:       HAVE_CONTEXT_TRACKING_USER
+#         description:   arch supports user context tracking for NO_HZ_FULL
 #
     -----------------------
     |         arch |status|
diff --git a/arch/Kconfig b/arch/Kconfig
index 1bf29ce754af..7a8cd4d67d9c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -769,7 +769,7 @@ config HAVE_ARCH_WITHIN_STACK_FRAMES
 	  and similar) by implementing an inline arch_within_stack_frames(),
 	  which is used by CONFIG_HARDENED_USERCOPY.
 
-config HAVE_CONTEXT_TRACKING
+config HAVE_CONTEXT_TRACKING_USER
 	bool
 	help
 	  Provide kernel/user boundaries probes necessary for subsystems
@@ -780,7 +780,7 @@ config HAVE_CONTEXT_TRACKING
 	  protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
 	  handling on irq exit still need to be protected.
 
-config HAVE_CONTEXT_TRACKING_OFFSTACK
+config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 	bool
 	help
 	  Architecture neither relies on exception_enter()/exception_exit()
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 2e8091e2d8a8..64eb31946598 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -84,7 +84,7 @@ config ARM
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if ARM_LPAE
 	select HAVE_ARM_SMCCC if CPU_V7
 	select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
-	select HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_BUILDTIME_MCOUNT_SORT
 	select HAVE_DEBUG_KMEMLEAK if !XIP_KERNEL
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 90d40f4d56cf..393d3945a43f 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -28,7 +28,7 @@
 #include "entry-header.S"
 
 saved_psr	.req	r8
-#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
+#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
 saved_pc	.req	r9
 #define TRACE(x...) x
 #else
@@ -38,7 +38,7 @@ saved_pc	.req	lr
 
 	.section .entry.text,"ax",%progbits
 	.align	5
-#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING) || \
+#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING_USER) || \
 	IS_ENABLED(CONFIG_DEBUG_RSEQ))
 /*
  * This is the fast syscall return path.  We do as little as possible here,
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S
index 0c14dcc43e58..8a54ff24bed0 100644
--- a/arch/arm/kernel/entry-header.S
+++ b/arch/arm/kernel/entry-header.S
@@ -367,7 +367,7 @@ ALT_UP_B(.L1_\@)
  * between user and kernel mode.
  */
 	.macro ct_user_exit, save = 1
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	.if	\save
 	stmdb   sp!, {r0-r3, ip, lr}
 	bl	user_exit_callable
@@ -379,7 +379,7 @@ ALT_UP_B(.L1_\@)
 	.endm
 
 	.macro ct_user_enter, save = 1
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	.if	\save
 	stmdb   sp!, {r0-r3, ip, lr}
 	bl	user_enter_callable
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 57c4c995965f..6e8757b89a54 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -171,7 +171,7 @@ config ARM64
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
-	select HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 75ef86605d69..171b59901214 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -42,7 +42,7 @@ config CSKY
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_SECCOMP_FILTER
-	select HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select HAVE_DEBUG_BUGVERBOSE
 	select HAVE_DEBUG_KMEMLEAK
diff --git a/arch/csky/kernel/entry.S b/arch/csky/kernel/entry.S
index bc734d17c16f..547b4cd1b24b 100644
--- a/arch/csky/kernel/entry.S
+++ b/arch/csky/kernel/entry.S
@@ -19,7 +19,7 @@
 .endm
 
 .macro	context_tracking
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	mfcr	a0, epsr
 	btsti	a0, 31
 	bt	1f
@@ -159,7 +159,7 @@ ret_from_exception:
 	and	r10, r9
 	cmpnei	r10, 0
 	bt	exit_work
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	jbsr	user_enter_callable
 #endif
 1:
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index de3b32a507d2..d0048cddd558 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -56,7 +56,7 @@ config MIPS
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES
 	select HAVE_ASM_MODVERSIONS
-	select HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_TIF_NOHZ
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_DEBUG_KMEMLEAK
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 174edabb74fa..f2fddc09a345 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -197,7 +197,7 @@ config PPC
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ASM_MODVERSIONS
-	select HAVE_CONTEXT_TRACKING		if PPC64
+	select HAVE_CONTEXT_TRACKING_USER		if PPC64
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DEBUG_STACKOVERFLOW
diff --git a/arch/powerpc/include/asm/context_tracking.h b/arch/powerpc/include/asm/context_tracking.h
index f2682b28b050..4b63931c49e0 100644
--- a/arch/powerpc/include/asm/context_tracking.h
+++ b/arch/powerpc/include/asm/context_tracking.h
@@ -2,7 +2,7 @@
 #ifndef _ASM_POWERPC_CONTEXT_TRACKING_H
 #define _ASM_POWERPC_CONTEXT_TRACKING_H
 
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 #define SCHEDULE_USER bl	schedule_user
 #else
 #define SCHEDULE_USER bl	schedule
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 00fd9c548f26..08316de9fa9f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -83,7 +83,7 @@ config RISCV
 	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_VMAP_STACK if MMU && 64BIT
 	select HAVE_ASM_MODVERSIONS
-	select HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS if MMU
 	select HAVE_EBPF_JIT if MMU
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index ecd132af2edf..fba900eaa0b8 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -111,7 +111,7 @@ _save_context:
 	call __trace_hardirqs_off
 #endif
 
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	/* If previous state is in user mode, call user_exit_callable(). */
 	li   a0, SR_PP
 	and a0, s1, a0
@@ -176,7 +176,7 @@ handle_syscall:
 	 */
 	csrs CSR_STATUS, SR_IE
 #endif
-#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
+#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
 	/* Recover a0 - a7 for system calls */
 	REG_L a0, PT_A0(sp)
 	REG_L a1, PT_A1(sp)
@@ -255,7 +255,7 @@ resume_userspace:
 	andi s1, s0, _TIF_WORK_MASK
 	bnez s1, work_pending
 
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	call user_enter_callable
 #endif
 
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 9200bc04701c..be50eae3ab0d 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -71,7 +71,7 @@ config SPARC64
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_SYSCALL_TRACEPOINTS
-	select HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER
 	select HAVE_TIF_NOHZ
 	select HAVE_DEBUG_KMEMLEAK
 	select IOMMU_HELPER
diff --git a/arch/sparc/kernel/rtrap_64.S b/arch/sparc/kernel/rtrap_64.S
index c5fd4b450d9b..eef102765a7e 100644
--- a/arch/sparc/kernel/rtrap_64.S
+++ b/arch/sparc/kernel/rtrap_64.S
@@ -15,7 +15,7 @@
 #include <asm/visasm.h>
 #include <asm/processor.h>
 
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 # define SCHEDULE_USER schedule_user
 #else
 # define SCHEDULE_USER schedule
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b0142e01002e..368a1c5cbb08 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -185,8 +185,8 @@ config X86
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
-	select HAVE_CONTEXT_TRACKING		if X86_64
-	select HAVE_CONTEXT_TRACKING_OFFSTACK	if HAVE_CONTEXT_TRACKING
+	select HAVE_CONTEXT_TRACKING_USER		if X86_64
+	select HAVE_CONTEXT_TRACKING_USER_OFFSTACK	if HAVE_CONTEXT_TRACKING_USER
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_OBJTOOL_MCOUNT		if STACK_VALIDATION
 	select HAVE_BUILDTIME_MCOUNT_SORT
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 63259fece7c7..e35ae66b4794 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -10,7 +10,7 @@
 #include <asm/ptrace.h>
 
 
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 extern void ct_cpu_track_user(int cpu);
 
 /* Called with interrupts disabled.  */
@@ -52,7 +52,7 @@ static inline enum ctx_state exception_enter(void)
 {
 	enum ctx_state prev_ctx;
 
-	if (IS_ENABLED(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK) ||
+	if (IS_ENABLED(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK) ||
 	    !context_tracking_enabled())
 		return 0;
 
@@ -65,7 +65,7 @@ static inline enum ctx_state exception_enter(void)
 
 static inline void exception_exit(enum ctx_state prev_ctx)
 {
-	if (!IS_ENABLED(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK) &&
+	if (!IS_ENABLED(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK) &&
 	    context_tracking_enabled()) {
 		if (prev_ctx != CONTEXT_KERNEL)
 			ct_user_enter(prev_ctx);
@@ -109,14 +109,14 @@ static inline enum ctx_state ct_state(void) { return CONTEXT_DISABLED; }
 static __always_inline bool context_tracking_guest_enter(void) { return false; }
 static inline void context_tracking_guest_exit(void) { }
 
-#endif /* !CONFIG_CONTEXT_TRACKING */
+#endif /* !CONFIG_CONTEXT_TRACKING_USER */
 
 #define CT_WARN_ON(cond) WARN_ON(context_tracking_enabled() && (cond))
 
-#ifdef CONFIG_CONTEXT_TRACKING_FORCE
+#ifdef CONFIG_CONTEXT_TRACKING_USER_FORCE
 extern void context_tracking_init(void);
 #else
 static inline void context_tracking_init(void) { }
-#endif /* CONFIG_CONTEXT_TRACKING_FORCE */
+#endif /* CONFIG_CONTEXT_TRACKING_USER_FORCE */
 
 #endif
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 02be3ac2040d..913acfee5dbf 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -22,7 +22,7 @@ struct context_tracking {
 	} state;
 };
 
-#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 extern struct static_key_false context_tracking_key;
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
@@ -45,6 +45,6 @@ static inline bool context_tracking_enabled_this_cpu(void)
 static inline bool context_tracking_enabled(void) { return false; }
 static inline bool context_tracking_enabled_cpu(int cpu) { return false; }
 static inline bool context_tracking_enabled_this_cpu(void) { return false; }
-#endif /* CONFIG_CONTEXT_TRACKING */
+#endif /* CONFIG_CONTEXT_TRACKING_USER */
 
 #endif
diff --git a/init/Kconfig b/init/Kconfig
index ddcbefe535e9..3d88ecadf771 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -502,11 +502,11 @@ config VIRT_CPU_ACCOUNTING_NATIVE
 
 config VIRT_CPU_ACCOUNTING_GEN
 	bool "Full dynticks CPU time accounting"
-	depends on HAVE_CONTEXT_TRACKING
+	depends on HAVE_CONTEXT_TRACKING_USER
 	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 	depends on GENERIC_CLOCKEVENTS
 	select VIRT_CPU_ACCOUNTING
-	select CONTEXT_TRACKING
+	select CONTEXT_TRACKING_USER
 	help
 	  Select this option to enable task and CPU time accounting on full
 	  dynticks systems. This accounting is implemented by watching every
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index f48eaad314ba..da067a36b326 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -22,6 +22,8 @@
 #include <linux/export.h>
 #include <linux/kprobes.h>
 
+#ifdef CONFIG_CONTEXT_TRACKING_USER
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/context_tracking.h>
 
@@ -238,7 +240,7 @@ void __init ct_cpu_track_user(int cpu)
 	initialized = true;
 }
 
-#ifdef CONFIG_CONTEXT_TRACKING_FORCE
+#ifdef CONFIG_CONTEXT_TRACKING_USER_FORCE
 void __init context_tracking_init(void)
 {
 	int cpu;
@@ -247,3 +249,5 @@ void __init context_tracking_init(void)
 		ct_cpu_track_user(cpu);
 }
 #endif
+
+#endif /* #ifdef CONFIG_CONTEXT_TRACKING_USER */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 068c088e9584..f1a31cd1e726 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6483,7 +6483,7 @@ void __sched schedule_idle(void)
 	} while (need_resched());
 }
 
-#if defined(CONFIG_CONTEXT_TRACKING) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK)
+#if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK)
 asmlinkage __visible void __sched schedule_user(void)
 {
 	/*
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 27b7868b5c30..aad89cc96787 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -111,7 +111,7 @@ config NO_HZ_FULL
 	# NO_HZ_COMMON dependency
 	# We need at least one periodic CPU for timekeeping
 	depends on SMP
-	depends on HAVE_CONTEXT_TRACKING
+	depends on HAVE_CONTEXT_TRACKING_USER
 	# VIRT_CPU_ACCOUNTING_GEN dependency
 	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select NO_HZ_COMMON
@@ -140,28 +140,32 @@ endchoice
 config CONTEXT_TRACKING
        bool
 
-config CONTEXT_TRACKING_FORCE
-	bool "Force context tracking"
-	depends on CONTEXT_TRACKING
+config CONTEXT_TRACKING_USER
+       select CONTEXT_TRACKING
+       bool
+
+config CONTEXT_TRACKING_USER_FORCE
+	bool "Force user context tracking"
+	depends on CONTEXT_TRACKING_USER
 	default y if !NO_HZ_FULL
 	help
 	  The major pre-requirement for full dynticks to work is to
-	  support the context tracking subsystem. But there are also
+	  support the user context tracking subsystem. But there are also
 	  other dependencies to provide in order to make the full
 	  dynticks working.
 
 	  This option stands for testing when an arch implements the
-	  context tracking backend but doesn't yet fulfill all the
+	  user context tracking backend but doesn't yet fulfill all the
 	  requirements to make the full dynticks feature working.
 	  Without the full dynticks, there is no way to test the support
-	  for context tracking and the subsystems that rely on it: RCU
+	  for user context tracking and the subsystems that rely on it: RCU
 	  userspace extended quiescent state and tickless cputime
 	  accounting. This option copes with the absence of the full
-	  dynticks subsystem by forcing the context tracking on all
+	  dynticks subsystem by forcing the user context tracking on all
 	  CPUs in the system.
 
 	  Say Y only if you're working on the development of an
-	  architecture backend for the context tracking.
+	  architecture backend for the user context tracking.
 
 	  Say N otherwise, this option brings an overhead that you
 	  don't want in production.
-- 
2.25.1

[PATCH 10/21] context_tracking: Take idle eqs entrypoints over RCU

[Frederic Weisbecker]

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         | 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

[PATCH 11/21] context_tracking: Take IRQ eqs entrypoints over RCU

[Frederic Weisbecker]

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

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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>
---
 .../RCU/Design/Requirements/Requirements.rst  | 10 ++++----
 Documentation/RCU/stallwarn.rst               |  4 ++--
 arch/Kconfig                                  |  2 +-
 arch/arm64/kernel/entry-common.c              |  6 ++---
 arch/x86/mm/fault.c                           |  2 +-
 drivers/cpuidle/cpuidle-psci.c                |  8 +++----
 drivers/cpuidle/cpuidle-riscv-sbi.c           |  8 +++----
 include/linux/context_tracking_irq.h          | 17 +++++++++++++
 include/linux/context_tracking_state.h        |  1 +
 include/linux/entry-common.h                  | 10 ++++----
 include/linux/rcupdate.h                      |  5 ++--
 include/linux/tracepoint.h                    |  4 ++--
 kernel/context_tracking.c                     | 24 +++++++++++++++++--
 kernel/cpu_pm.c                               |  8 +++----
 kernel/entry/common.c                         | 12 +++++-----
 kernel/softirq.c                              |  4 ++--
 kernel/trace/trace.c                          |  6 ++---
 17 files changed, 85 insertions(+), 46 deletions(-)
 create mode 100644 include/linux/context_tracking_irq.h

diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst
index 04ed8bf27a0e..2a657fd2bca3 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.rst
+++ b/Documentation/RCU/Design/Requirements/Requirements.rst
@@ -1844,10 +1844,10 @@ that meets this requirement.
 
 Furthermore, NMI handlers can be interrupted by what appear to RCU to be
 normal interrupts. One way that this can happen is for code that
-directly invokes rcu_irq_enter() and rcu_irq_exit() to be called
+directly invokes ct_irq_enter() and ct_irq_exit() to be called
 from an NMI handler. This astonishing fact of life prompted the current
-code structure, which has rcu_irq_enter() invoking
-rcu_nmi_enter() and rcu_irq_exit() invoking rcu_nmi_exit().
+code structure, which has ct_irq_enter() invoking
+rcu_nmi_enter() and ct_irq_exit() invoking rcu_nmi_exit().
 And yes, I also learned of this requirement the hard way.
 
 Loadable Modules
@@ -2195,7 +2195,7 @@ scheduling-clock interrupt be enabled when RCU needs it to be:
    sections, and RCU believes this CPU to be idle, no problem. This
    sort of thing is used by some architectures for light-weight
    exception handlers, which can then avoid the overhead of
-   rcu_irq_enter() and rcu_irq_exit() at exception entry and
+   ct_irq_enter() and ct_irq_exit() at exception entry and
    exit, respectively. Some go further and avoid the entireties of
    irq_enter() and irq_exit().
    Just make very sure you are running some of your tests with
@@ -2226,7 +2226,7 @@ scheduling-clock interrupt be enabled when RCU needs it to be:
 +-----------------------------------------------------------------------+
 | **Answer**:                                                           |
 +-----------------------------------------------------------------------+
-| One approach is to do ``rcu_irq_exit();rcu_irq_enter();`` every so    |
+| One approach is to do ``ct_irq_exit();ct_irq_enter();`` every so    |
 | often. But given that long-running interrupt handlers can cause other |
 | problems, not least for response time, shouldn't you work to keep     |
 | your interrupt handler's runtime within reasonable bounds?            |
diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst
index bdd52b40f307..7858c3afa1f4 100644
--- a/Documentation/RCU/stallwarn.rst
+++ b/Documentation/RCU/stallwarn.rst
@@ -98,11 +98,11 @@ warnings:
 
 -	A low-level kernel issue that either fails to invoke one of the
 	variants of rcu_user_enter(), rcu_user_exit(), ct_idle_enter(),
-	ct_idle_exit(), rcu_irq_enter(), or rcu_irq_exit() on the one
+	ct_idle_exit(), ct_irq_enter(), or ct_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
-	rcu_irq_enter() or rcu_irq_exit(), respectively.  Building your
+	ct_irq_enter() or ct_irq_exit(), respectively.  Building your
 	kernel with CONFIG_RCU_EQS_DEBUG=y can help track down these types
 	of issues, which sometimes arise in architecture-specific code.
 
diff --git a/arch/Kconfig b/arch/Kconfig
index 7a8cd4d67d9c..888f9725b20b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -777,7 +777,7 @@ config HAVE_CONTEXT_TRACKING_USER
 	  Syscalls need to be wrapped inside user_exit()-user_enter(), either
 	  optimized behind static key or through the slow path using TIF_NOHZ
 	  flag. Exceptions handlers must be wrapped as well. Irqs are already
-	  protected inside rcu_irq_enter/rcu_irq_exit() but preemption or signal
+	  protected inside ct_irq_enter/ct_irq_exit() but preemption or signal
 	  handling on irq exit still need to be protected.
 
 config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 878c65aa7206..a1490e8bf5d4 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -41,7 +41,7 @@ static __always_inline void __enter_from_kernel_mode(struct pt_regs *regs)
 
 	if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
 		lockdep_hardirqs_off(CALLER_ADDR0);
-		rcu_irq_enter();
+		ct_irq_enter();
 		trace_hardirqs_off_finish();
 
 		regs->exit_rcu = true;
@@ -76,7 +76,7 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs)
 		if (regs->exit_rcu) {
 			trace_hardirqs_on_prepare();
 			lockdep_hardirqs_on_prepare(CALLER_ADDR0);
-			rcu_irq_exit();
+			ct_irq_exit();
 			lockdep_hardirqs_on(CALLER_ADDR0);
 			return;
 		}
@@ -84,7 +84,7 @@ static __always_inline void __exit_to_kernel_mode(struct pt_regs *regs)
 		trace_hardirqs_on();
 	} else {
 		if (regs->exit_rcu)
-			rcu_irq_exit();
+			ct_irq_exit();
 	}
 }
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index d0074c6ed31a..b781785b1ff3 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1526,7 +1526,7 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 
 	/*
 	 * Entry handling for valid #PF from kernel mode is slightly
-	 * different: RCU is already watching and rcu_irq_enter() must not
+	 * different: RCU is already watching and ct_irq_enter() must not
 	 * be invoked because a kernel fault on a user space address might
 	 * sleep.
 	 *
diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
index b51b5df08450..fe31b2d522b3 100644
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -68,12 +68,12 @@ static int __psci_enter_domain_idle_state(struct cpuidle_device *dev,
 		return -1;
 
 	/* Do runtime PM to manage a hierarchical CPU toplogy. */
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	if (s2idle)
 		dev_pm_genpd_suspend(pd_dev);
 	else
 		pm_runtime_put_sync_suspend(pd_dev);
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 
 	state = psci_get_domain_state();
 	if (!state)
@@ -81,12 +81,12 @@ static int __psci_enter_domain_idle_state(struct cpuidle_device *dev,
 
 	ret = psci_cpu_suspend_enter(state) ? -1 : idx;
 
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	if (s2idle)
 		dev_pm_genpd_resume(pd_dev);
 	else
 		pm_runtime_get_sync(pd_dev);
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 
 	cpu_pm_exit();
 
diff --git a/drivers/cpuidle/cpuidle-riscv-sbi.c b/drivers/cpuidle/cpuidle-riscv-sbi.c
index b459eda2cd37..759603181d53 100644
--- a/drivers/cpuidle/cpuidle-riscv-sbi.c
+++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
@@ -115,12 +115,12 @@ static int __sbi_enter_domain_idle_state(struct cpuidle_device *dev,
 		return -1;
 
 	/* Do runtime PM to manage a hierarchical CPU toplogy. */
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	if (s2idle)
 		dev_pm_genpd_suspend(pd_dev);
 	else
 		pm_runtime_put_sync_suspend(pd_dev);
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 
 	if (sbi_is_domain_state_available())
 		state = sbi_get_domain_state();
@@ -129,12 +129,12 @@ static int __sbi_enter_domain_idle_state(struct cpuidle_device *dev,
 
 	ret = sbi_suspend(state) ? -1 : idx;
 
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	if (s2idle)
 		dev_pm_genpd_resume(pd_dev);
 	else
 		pm_runtime_get_sync(pd_dev);
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 
 	cpu_pm_exit();
 
diff --git a/include/linux/context_tracking_irq.h b/include/linux/context_tracking_irq.h
new file mode 100644
index 000000000000..60e3ed15a04e
--- /dev/null
+++ b/include/linux/context_tracking_irq.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CONTEXT_TRACKING_IRQ_H
+#define _LINUX_CONTEXT_TRACKING_IRQ_H
+
+#ifdef CONFIG_CONTEXT_TRACKING
+void ct_irq_enter(void);
+void ct_irq_exit(void);
+void ct_irq_enter_irqson(void);
+void ct_irq_exit_irqson(void);
+#else
+static inline void ct_irq_enter(void) { }
+static inline void ct_irq_exit(void) { }
+static inline void ct_irq_enter_irqson(void) { }
+static inline void ct_irq_exit_irqson(void) { }
+#endif
+
+#endif
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 913acfee5dbf..7b46b43b8c98 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -4,6 +4,7 @@
 
 #include <linux/percpu.h>
 #include <linux/static_key.h>
+#include <linux/context_tracking_irq.h>
 
 struct context_tracking {
 	/*
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index ab78bd4c2eb0..2d4cf0b5fe1c 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -357,7 +357,7 @@ void irqentry_exit_to_user_mode(struct pt_regs *regs);
 /**
  * struct irqentry_state - Opaque object for exception state storage
  * @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
- *            exit path has to invoke rcu_irq_exit().
+ *            exit path has to invoke ct_irq_exit().
  * @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
  *           lockdep state is restored correctly on exit from nmi.
  *
@@ -395,12 +395,12 @@ typedef struct irqentry_state {
  *
  * For kernel mode entries RCU handling is done conditional. If RCU is
  * watching then the only RCU requirement is to check whether the tick has
- * to be restarted. If RCU is not watching then rcu_irq_enter() has to be
- * invoked on entry and rcu_irq_exit() on exit.
+ * to be restarted. If RCU is not watching then ct_irq_enter() has to be
+ * invoked on entry and ct_irq_exit() on exit.
  *
- * Avoiding the rcu_irq_enter/exit() calls is an optimization but also
+ * Avoiding the ct_irq_enter/exit() calls is an optimization but also
  * solves the problem of kernel mode pagefaults which can schedule, which
- * is not possible after invoking rcu_irq_enter() without undoing it.
+ * is not possible after invoking ct_irq_enter() without undoing it.
  *
  * For user mode entries irqentry_enter_from_user_mode() is invoked to
  * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index d3b25e65f144..923e4fa04338 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -29,6 +29,7 @@
 #include <linux/lockdep.h>
 #include <asm/processor.h>
 #include <linux/cpumask.h>
+#include <linux/context_tracking_irq.h>
 
 #define ULONG_CMP_GE(a, b)	(ULONG_MAX / 2 >= (a) - (b))
 #define ULONG_CMP_LT(a, b)	(ULONG_MAX / 2 < (a) - (b))
@@ -144,9 +145,9 @@ static inline void rcu_nocb_flush_deferred_wakeup(void) { }
  */
 #define RCU_NONIDLE(a) \
 	do { \
-		rcu_irq_enter_irqson(); \
+		ct_irq_enter_irqson(); \
 		do { a; } while (0); \
-		rcu_irq_exit_irqson(); \
+		ct_irq_exit_irqson(); \
 	} while (0)
 
 /*
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 28031b15f878..55717a2eda08 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -200,13 +200,13 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 		 */							\
 		if (rcuidle) {						\
 			__idx = srcu_read_lock_notrace(&tracepoint_srcu);\
-			rcu_irq_enter_irqson();				\
+			ct_irq_enter_irqson();				\
 		}							\
 									\
 		__DO_TRACE_CALL(name, TP_ARGS(args));			\
 									\
 		if (rcuidle) {						\
-			rcu_irq_exit_irqson();				\
+			ct_irq_exit_irqson();				\
 			srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\
 		}							\
 									\
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 987f0b2a3962..a8f6d1580144 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -75,7 +75,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
 			 * At this stage, only low level arch entry code remains and
 			 * then we'll run in userspace. We can assume there won't be
 			 * any RCU read-side critical section until the next call to
-			 * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency
+			 * user_exit() or ct_irq_enter(). Let's remove RCU's dependency
 			 * on the tick.
 			 */
 			if (state == CONTEXT_USER) {
@@ -117,7 +117,7 @@ void ct_user_enter(enum ctx_state state)
 	/*
 	 * Some contexts may involve an exception occuring in an irq,
 	 * leading to that nesting:
-	 * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
+	 * ct_irq_enter() rcu_user_exit() rcu_user_exit() ct_irq_exit()
 	 * This would mess up the dyntick_nesting count though. And rcu_irq_*()
 	 * helpers are enough to protect RCU uses inside the exception. So
 	 * just return immediately if we detect we are in an IRQ.
@@ -263,3 +263,23 @@ void ct_idle_exit(void)
 	rcu_idle_exit();
 }
 EXPORT_SYMBOL_GPL(ct_idle_exit);
+
+noinstr void ct_irq_enter(void)
+{
+	rcu_irq_enter();
+}
+
+noinstr void ct_irq_exit(void)
+{
+	rcu_irq_exit();
+}
+
+void ct_irq_enter_irqson(void)
+{
+	rcu_irq_enter_irqson();
+}
+
+void ct_irq_exit_irqson(void)
+{
+	rcu_irq_exit_irqson();
+}
diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
index 246efc74e3f3..ba4ba71facf9 100644
--- a/kernel/cpu_pm.c
+++ b/kernel/cpu_pm.c
@@ -35,11 +35,11 @@ static int cpu_pm_notify(enum cpu_pm_event event)
 	 * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know
 	 * this.
 	 */
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	rcu_read_lock();
 	ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
 	rcu_read_unlock();
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 
 	return notifier_to_errno(ret);
 }
@@ -49,11 +49,11 @@ static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event ev
 	unsigned long flags;
 	int ret;
 
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
 	ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL);
 	raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 
 	return notifier_to_errno(ret);
 }
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index e57a224d6b79..9a89386696ba 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -321,7 +321,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 	}
 
 	/*
-	 * If this entry hit the idle task invoke rcu_irq_enter() whether
+	 * If this entry hit the idle task invoke ct_irq_enter() whether
 	 * RCU is watching or not.
 	 *
 	 * Interrupts can nest when the first interrupt invokes softirq
@@ -332,12 +332,12 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 	 * not nested into another interrupt.
 	 *
 	 * Checking for rcu_is_watching() here would prevent the nesting
-	 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
+	 * interrupt to invoke ct_irq_enter(). If that nested interrupt is
 	 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
 	 * assume that it is the first interrupt and eventually claim
 	 * quiescent state and end grace periods prematurely.
 	 *
-	 * Unconditionally invoke rcu_irq_enter() so RCU state stays
+	 * Unconditionally invoke ct_irq_enter() so RCU state stays
 	 * consistent.
 	 *
 	 * TINY_RCU does not support EQS, so let the compiler eliminate
@@ -350,7 +350,7 @@ noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 		 * as in irqentry_enter_from_user_mode().
 		 */
 		lockdep_hardirqs_off(CALLER_ADDR0);
-		rcu_irq_enter();
+		ct_irq_enter();
 		instrumentation_begin();
 		trace_hardirqs_off_finish();
 		instrumentation_end();
@@ -418,7 +418,7 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 			trace_hardirqs_on_prepare();
 			lockdep_hardirqs_on_prepare(CALLER_ADDR0);
 			instrumentation_end();
-			rcu_irq_exit();
+			ct_irq_exit();
 			lockdep_hardirqs_on(CALLER_ADDR0);
 			return;
 		}
@@ -436,7 +436,7 @@ noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 		 * was not watching on entry.
 		 */
 		if (state.exit_rcu)
-			rcu_irq_exit();
+			ct_irq_exit();
 	}
 }
 
diff --git a/kernel/softirq.c b/kernel/softirq.c
index fac801815554..7db9db832b31 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -607,7 +607,7 @@ void irq_enter_rcu(void)
  */
 void irq_enter(void)
 {
-	rcu_irq_enter();
+	ct_irq_enter();
 	irq_enter_rcu();
 }
 
@@ -659,7 +659,7 @@ void irq_exit_rcu(void)
 void irq_exit(void)
 {
 	__irq_exit_rcu();
-	rcu_irq_exit();
+	ct_irq_exit();
 	 /* must be last! */
 	lockdep_hardirq_exit();
 }
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f4de111fa18f..85e519cc0af9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3104,15 +3104,15 @@ void __trace_stack(struct trace_array *tr, unsigned int trace_ctx,
 	/*
 	 * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
 	 * but if the above rcu_is_watching() failed, then the NMI
-	 * triggered someplace critical, and rcu_irq_enter() should
+	 * triggered someplace critical, and ct_irq_enter() should
 	 * not be called from NMI.
 	 */
 	if (unlikely(in_nmi()))
 		return;
 
-	rcu_irq_enter_irqson();
+	ct_irq_enter_irqson();
 	__ftrace_trace_stack(buffer, trace_ctx, skip, NULL);
-	rcu_irq_exit_irqson();
+	ct_irq_exit_irqson();
 }
 
 /**
-- 
2.25.1

[PATCH 12/21] context_tracking: Take NMI eqs entrypoints over RCU

[Frederic Weisbecker]

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

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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/Design/Requirements/Requirements.rst |  2 +-
 arch/Kconfig                                           |  2 +-
 arch/arm64/kernel/entry-common.c                       |  8 ++++----
 include/linux/context_tracking_irq.h                   |  4 ++++
 include/linux/hardirq.h                                |  4 ++--
 kernel/context_tracking.c                              | 10 ++++++++++
 kernel/entry/common.c                                  |  4 ++--
 kernel/extable.c                                       |  4 ++--
 kernel/trace/trace.c                                   |  2 +-
 9 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst
index 2a657fd2bca3..ac323f2af19b 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.rst
+++ b/Documentation/RCU/Design/Requirements/Requirements.rst
@@ -1847,7 +1847,7 @@ normal interrupts. One way that this can happen is for code that
 directly invokes ct_irq_enter() and ct_irq_exit() to be called
 from an NMI handler. This astonishing fact of life prompted the current
 code structure, which has ct_irq_enter() invoking
-rcu_nmi_enter() and ct_irq_exit() invoking rcu_nmi_exit().
+ct_nmi_enter() and ct_irq_exit() invoking ct_nmi_exit().
 And yes, I also learned of this requirement the hard way.
 
 Loadable Modules
diff --git a/arch/Kconfig b/arch/Kconfig
index 888f9725b20b..a1150a190bf6 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -792,7 +792,7 @@ config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 
 	  - Critical entry code isn't preemptible (or better yet:
 	    not interruptible).
-	  - No use of RCU read side critical sections, unless rcu_nmi_enter()
+	  - No use of RCU read side critical sections, unless ct_nmi_enter()
 	    got called.
 	  - No use of instrumentation, unless instrumentation_begin() got
 	    called.
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index a1490e8bf5d4..b8fcdd777a8a 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -161,7 +161,7 @@ static void noinstr arm64_enter_nmi(struct pt_regs *regs)
 	__nmi_enter();
 	lockdep_hardirqs_off(CALLER_ADDR0);
 	lockdep_hardirq_enter();
-	rcu_nmi_enter();
+	ct_nmi_enter();
 
 	trace_hardirqs_off_finish();
 	ftrace_nmi_enter();
@@ -182,7 +182,7 @@ static void noinstr arm64_exit_nmi(struct pt_regs *regs)
 		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
 	}
 
-	rcu_nmi_exit();
+	ct_nmi_exit();
 	lockdep_hardirq_exit();
 	if (restore)
 		lockdep_hardirqs_on(CALLER_ADDR0);
@@ -199,7 +199,7 @@ static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
 	regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
 
 	lockdep_hardirqs_off(CALLER_ADDR0);
-	rcu_nmi_enter();
+	ct_nmi_enter();
 
 	trace_hardirqs_off_finish();
 }
@@ -218,7 +218,7 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
 		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
 	}
 
-	rcu_nmi_exit();
+	ct_nmi_exit();
 	if (restore)
 		lockdep_hardirqs_on(CALLER_ADDR0);
 }
diff --git a/include/linux/context_tracking_irq.h b/include/linux/context_tracking_irq.h
index 60e3ed15a04e..11043bf724b7 100644
--- a/include/linux/context_tracking_irq.h
+++ b/include/linux/context_tracking_irq.h
@@ -7,11 +7,15 @@ void ct_irq_enter(void);
 void ct_irq_exit(void);
 void ct_irq_enter_irqson(void);
 void ct_irq_exit_irqson(void);
+void ct_nmi_enter(void);
+void ct_nmi_exit(void);
 #else
 static inline void ct_irq_enter(void) { }
 static inline void ct_irq_exit(void) { }
 static inline void ct_irq_enter_irqson(void) { }
 static inline void ct_irq_exit_irqson(void) { }
+static inline void ct_nmi_enter(void) { }
+static inline void ct_nmi_exit(void) { }
 #endif
 
 #endif
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 76878b357ffa..345cdbe9c1b7 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -124,7 +124,7 @@ extern void rcu_nmi_exit(void);
 	do {							\
 		__nmi_enter();					\
 		lockdep_hardirq_enter();			\
-		rcu_nmi_enter();				\
+		ct_nmi_enter();				\
 		instrumentation_begin();			\
 		ftrace_nmi_enter();				\
 		instrumentation_end();				\
@@ -143,7 +143,7 @@ extern void rcu_nmi_exit(void);
 		instrumentation_begin();			\
 		ftrace_nmi_exit();				\
 		instrumentation_end();				\
-		rcu_nmi_exit();					\
+		ct_nmi_exit();					\
 		lockdep_hardirq_exit();				\
 		__nmi_exit();					\
 	} while (0)
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index a8f6d1580144..7aa5b0cad19e 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -283,3 +283,13 @@ void ct_irq_exit_irqson(void)
 {
 	rcu_irq_exit_irqson();
 }
+
+noinstr void ct_nmi_enter(void)
+{
+	rcu_nmi_enter();
+}
+
+noinstr void ct_nmi_exit(void)
+{
+	rcu_nmi_exit();
+}
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 9a89386696ba..256fb950a603 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -449,7 +449,7 @@ irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
 	__nmi_enter();
 	lockdep_hardirqs_off(CALLER_ADDR0);
 	lockdep_hardirq_enter();
-	rcu_nmi_enter();
+	ct_nmi_enter();
 
 	instrumentation_begin();
 	trace_hardirqs_off_finish();
@@ -469,7 +469,7 @@ void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
 	}
 	instrumentation_end();
 
-	rcu_nmi_exit();
+	ct_nmi_exit();
 	lockdep_hardirq_exit();
 	if (irq_state.lockdep)
 		lockdep_hardirqs_on(CALLER_ADDR0);
diff --git a/kernel/extable.c b/kernel/extable.c
index bda5e9761541..71f482581cab 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -114,7 +114,7 @@ int kernel_text_address(unsigned long addr)
 
 	/* Treat this like an NMI as it can happen anywhere */
 	if (no_rcu)
-		rcu_nmi_enter();
+		ct_nmi_enter();
 
 	if (is_module_text_address(addr))
 		goto out;
@@ -127,7 +127,7 @@ int kernel_text_address(unsigned long addr)
 	ret = 0;
 out:
 	if (no_rcu)
-		rcu_nmi_exit();
+		ct_nmi_exit();
 
 	return ret;
 }
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 85e519cc0af9..c096da6ea121 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3102,7 +3102,7 @@ void __trace_stack(struct trace_array *tr, unsigned int trace_ctx,
 	}
 
 	/*
-	 * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
+	 * When an NMI triggers, RCU is enabled via ct_nmi_enter(),
 	 * but if the above rcu_is_watching() failed, then the NMI
 	 * triggered someplace critical, and ct_irq_enter() should
 	 * not be called from NMI.
-- 
2.25.1

[PATCH 13/21] rcu/context-tracking: Remove rcu_irq_enter/exit()

[Frederic Weisbecker]

Now rcu_irq_enter/exit() is an unecessary middle call between
ct_irq_enter/exit() and nmi_irq_enter/exit(). Take this opportunity
to remove the former functions and move the comments above them to the
new entrypoints.

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>
---
 include/linux/rcutiny.h   |  4 --
 include/linux/rcutree.h   |  4 --
 kernel/context_tracking.c | 79 +++++++++++++++++++++++++++++++--
 kernel/rcu/tree.c         | 91 ---------------------------------------
 4 files changed, 75 insertions(+), 103 deletions(-)

diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index ab7e20dfb07b..5921d9ae7ab5 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -88,10 +88,6 @@ static inline void rcu_cpu_stall_reset(void) { }
 static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
 static inline void rcu_idle_enter(void) { }
 static inline void rcu_idle_exit(void) { }
-static inline void rcu_irq_enter(void) { }
-static inline void rcu_irq_exit_irqson(void) { }
-static inline void rcu_irq_enter_irqson(void) { }
-static inline void rcu_irq_exit(void) { }
 static inline void rcu_irq_exit_check_preempt(void) { }
 #define rcu_is_idle_cpu(cpu) \
 	(is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq())
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 20dbaa9a3882..cafe3fbf4272 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -49,10 +49,6 @@ void cond_synchronize_rcu(unsigned long oldstate);
 
 void rcu_idle_enter(void);
 void rcu_idle_exit(void);
-void rcu_irq_enter(void);
-void rcu_irq_exit(void);
-void rcu_irq_enter_irqson(void);
-void rcu_irq_exit_irqson(void);
 bool rcu_is_idle_cpu(int cpu);
 
 #ifdef CONFIG_PROVE_RCU
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 7aa5b0cad19e..a9570365c7f3 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -264,24 +264,95 @@ void ct_idle_exit(void)
 }
 EXPORT_SYMBOL_GPL(ct_idle_exit);
 
+/**
+ * ct_irq_enter - inform RCU that current CPU is entering irq away from idle
+ *
+ * Enter an interrupt handler, which might possibly result in exiting
+ * idle mode, in other words, entering the mode in which read-side critical
+ * sections can occur.  The caller must have disabled interrupts.
+ *
+ * Note that the Linux kernel is fully capable of entering an interrupt
+ * handler that it never exits, for example when doing upcalls to user mode!
+ * This code assumes that the idle loop never does upcalls to user mode.
+ * If your architecture's idle loop does do upcalls to user mode (or does
+ * anything else that results in unbalanced calls to the irq_enter() and
+ * irq_exit() functions), RCU will give you what you deserve, good and hard.
+ * But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
+ *
+ * If you add or remove a call to ct_irq_enter(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
 noinstr void ct_irq_enter(void)
 {
-	rcu_irq_enter();
+	lockdep_assert_irqs_disabled();
+	ct_nmi_enter();
 }
 
+/**
+ * ct_irq_exit - inform RCU that current CPU is exiting irq towards idle
+ *
+ * Exit from an interrupt handler, which might possibly result in entering
+ * idle mode, in other words, leaving the mode in which read-side critical
+ * sections can occur.  The caller must have disabled interrupts.
+ *
+ * This code assumes that the idle loop never does anything that might
+ * result in unbalanced calls to irq_enter() and irq_exit().  If your
+ * architecture's idle loop violates this assumption, RCU will give you what
+ * you deserve, good and hard.  But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
+ *
+ * If you add or remove a call to ct_irq_exit(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
 noinstr void ct_irq_exit(void)
 {
-	rcu_irq_exit();
+	lockdep_assert_irqs_disabled();
+	ct_nmi_exit();
 }
 
+/*
+ * Wrapper for ct_irq_enter() where interrupts are enabled.
+ *
+ * If you add or remove a call to ct_irq_enter_irqson(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_save() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
+ */
 void ct_irq_enter_irqson(void)
 {
-	rcu_irq_enter_irqson();
+	unsigned long flags;
+
+	local_irq_save(flags);
+	ct_irq_enter();
+	local_irq_restore(flags);
 }
 
+/*
+ * Wrapper for ct_irq_exit() where interrupts are enabled.
+ *
+ * If you add or remove a call to ct_irq_exit_irqson(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_restore() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
+ */
 void ct_irq_exit_irqson(void)
 {
-	rcu_irq_exit_irqson();
+	unsigned long flags;
+
+	local_irq_save(flags);
+	ct_irq_exit();
+	local_irq_restore(flags);
 }
 
 noinstr void ct_nmi_enter(void)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 92a288668e7c..38c23229103f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -789,31 +789,6 @@ noinstr void rcu_nmi_exit(void)
 		rcu_dynticks_task_enter();
 }
 
-/**
- * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
- *
- * Exit from an interrupt handler, which might possibly result in entering
- * idle mode, in other words, leaving the mode in which read-side critical
- * sections can occur.  The caller must have disabled interrupts.
- *
- * This code assumes that the idle loop never does anything that might
- * result in unbalanced calls to irq_enter() and irq_exit().  If your
- * architecture's idle loop violates this assumption, RCU will give you what
- * you deserve, good and hard.  But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- *
- * If you add or remove a call to rcu_irq_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void noinstr rcu_irq_exit(void)
-{
-	lockdep_assert_irqs_disabled();
-	rcu_nmi_exit();
-}
-
 #ifdef CONFIG_PROVE_RCU
 /**
  * rcu_irq_exit_check_preempt - Validate that scheduling is possible
@@ -832,25 +807,6 @@ void rcu_irq_exit_check_preempt(void)
 }
 #endif /* #ifdef CONFIG_PROVE_RCU */
 
-/*
- * Wrapper for rcu_irq_exit() where interrupts are enabled.
- *
- * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- *
- * FIXME: This function should be noinstr but the below local_irq_restore() is
- * unsafe because it involves illegal RCU uses through tracing and lockdep.
- * This must be fixed first.
- */
-void rcu_irq_exit_irqson(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	rcu_irq_exit();
-	local_irq_restore(flags);
-}
-
 /*
  * Exit an RCU extended quiescent state, which can be either the
  * idle loop or adaptive-tickless usermode execution.
@@ -1049,53 +1005,6 @@ noinstr void rcu_nmi_enter(void)
 	barrier();
 }
 
-/**
- * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
- *
- * Enter an interrupt handler, which might possibly result in exiting
- * idle mode, in other words, entering the mode in which read-side critical
- * sections can occur.  The caller must have disabled interrupts.
- *
- * Note that the Linux kernel is fully capable of entering an interrupt
- * handler that it never exits, for example when doing upcalls to user mode!
- * This code assumes that the idle loop never does upcalls to user mode.
- * If your architecture's idle loop does do upcalls to user mode (or does
- * anything else that results in unbalanced calls to the irq_enter() and
- * irq_exit() functions), RCU will give you what you deserve, good and hard.
- * But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- *
- * If you add or remove a call to rcu_irq_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_irq_enter(void)
-{
-	lockdep_assert_irqs_disabled();
-	rcu_nmi_enter();
-}
-
-/*
- * Wrapper for rcu_irq_enter() where interrupts are enabled.
- *
- * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- *
- * FIXME: This function should be noinstr but the below local_irq_save() is
- * unsafe because it involves illegal RCU uses through tracing and lockdep.
- * This must be fixed first.
- */
-void rcu_irq_enter_irqson(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	rcu_irq_enter();
-	local_irq_restore(flags);
-}
-
 /*
  * Check to see if any future non-offloaded RCU-related work will need
  * to be done by the current CPU, even if none need be done immediately,
-- 
2.25.1

[PATCH 14/21] rcu/context_tracking: Move dynticks counter to context tracking

[Frederic Weisbecker]

In order to prepare for merging RCU dynticks counter into the context
tracking state, move the rcu_data's dynticks field to the context
tracking structure. It will later be mixed within the context tracking
state itself.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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>
---
 include/linux/context_tracking_state.h | 27 ++++++++++++-
 kernel/context_tracking.c              |  9 +++--
 kernel/rcu/tree.c                      | 56 +++++++++++++-------------
 kernel/rcu/tree.h                      |  1 -
 kernel/rcu/tree_exp.h                  |  2 +-
 kernel/rcu/tree_stall.h                |  4 +-
 6 files changed, 61 insertions(+), 38 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 7b46b43b8c98..014dc431521b 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -7,6 +7,7 @@
 #include <linux/context_tracking_irq.h>
 
 struct context_tracking {
+#ifdef CONFIG_CONTEXT_TRACKING_USER
 	/*
 	 * When active is false, probes are unset in order
 	 * to minimize overhead: TIF flags are cleared
@@ -21,12 +22,34 @@ struct context_tracking {
 		CONTEXT_USER,
 		CONTEXT_GUEST,
 	} state;
+#endif
+	atomic_t dynticks;		/* Even value for idle, else odd. */
 };
 
-#ifdef CONFIG_CONTEXT_TRACKING_USER
-extern struct static_key_false context_tracking_key;
+#ifdef CONFIG_CONTEXT_TRACKING
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
+static __always_inline int ct_dynticks(void)
+{
+	return atomic_read(this_cpu_ptr(&context_tracking.dynticks));
+}
+
+static __always_inline int ct_dynticks_cpu(int cpu)
+{
+	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
+	return atomic_read(&ct->dynticks);
+}
+
+static __always_inline int ct_dynticks_cpu_acquire(int cpu)
+{
+	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
+	return atomic_read_acquire(&ct->state);
+}
+#endif
+
+#ifdef CONFIG_CONTEXT_TRACKING_USER
+extern struct static_key_false context_tracking_key;
+
 static __always_inline bool context_tracking_enabled(void)
 {
 	return static_branch_unlikely(&context_tracking_key);
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index a9570365c7f3..20be30c24723 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -30,9 +30,6 @@
 DEFINE_STATIC_KEY_FALSE(context_tracking_key);
 EXPORT_SYMBOL_GPL(context_tracking_key);
 
-DEFINE_PER_CPU(struct context_tracking, context_tracking);
-EXPORT_SYMBOL_GPL(context_tracking);
-
 static noinstr bool context_tracking_recursion_enter(void)
 {
 	int recursion;
@@ -252,6 +249,12 @@ void __init context_tracking_init(void)
 
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_USER */
 
+DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
+		.dynticks = ATOMIC_INIT(1),
+};
+EXPORT_SYMBOL_GPL(context_tracking);
+
+
 noinstr void ct_idle_enter(void)
 {
 	rcu_idle_enter();
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 38c23229103f..7667186731e3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -77,7 +77,6 @@
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
 	.dynticks_nesting = 1,
 	.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
-	.dynticks = ATOMIC_INIT(1),
 #ifdef CONFIG_RCU_NOCB_CPU
 	.cblist.flags = SEGCBLIST_RCU_CORE,
 #endif
@@ -268,7 +267,7 @@ void rcu_softirq_qs(void)
  */
 static noinline noinstr unsigned long rcu_dynticks_inc(int incby)
 {
-	return arch_atomic_add_return(incby, this_cpu_ptr(&rcu_data.dynticks));
+	return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.dynticks));
 }
 
 /*
@@ -324,9 +323,7 @@ static noinstr void rcu_dynticks_eqs_exit(void)
  */
 static void rcu_dynticks_eqs_online(void)
 {
-	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
-	if (atomic_read(&rdp->dynticks) & 0x1)
+	if (ct_dynticks() & 0x1)
 		return;
 	rcu_dynticks_inc(1);
 }
@@ -338,17 +335,17 @@ static void rcu_dynticks_eqs_online(void)
  */
 static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
 {
-	return !(arch_atomic_read(this_cpu_ptr(&rcu_data.dynticks)) & 0x1);
+	return !(arch_atomic_read(this_cpu_ptr(&context_tracking.dynticks)) & 0x1);
 }
 
 /*
  * Snapshot the ->dynticks counter with full ordering so as to allow
  * stable comparison of this counter with past and future snapshots.
  */
-static int rcu_dynticks_snap(struct rcu_data *rdp)
+static int rcu_dynticks_snap(int cpu)
 {
 	smp_mb();  // Fundamental RCU ordering guarantee.
-	return atomic_read_acquire(&rdp->dynticks);
+	return ct_dynticks_cpu_acquire(cpu);
 }
 
 /*
@@ -363,9 +360,7 @@ static bool rcu_dynticks_in_eqs(int snap)
 /* Return true if the specified CPU is currently idle from an RCU viewpoint.  */
 bool rcu_is_idle_cpu(int cpu)
 {
-	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
-
-	return rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp));
+	return rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
 }
 
 /*
@@ -375,7 +370,7 @@ bool rcu_is_idle_cpu(int cpu)
  */
 static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
 {
-	return snap != rcu_dynticks_snap(rdp);
+	return snap != rcu_dynticks_snap(rdp->cpu);
 }
 
 /*
@@ -384,11 +379,10 @@ static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
  */
 bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
 {
-	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 	int snap;
 
 	// If not quiescent, force back to earlier extended quiescent state.
-	snap = atomic_read(&rdp->dynticks) & ~0x1;
+	snap = ct_dynticks_cpu(cpu) & ~0x1;
 
 	smp_rmb(); // Order ->dynticks and *vp reads.
 	if (READ_ONCE(*vp))
@@ -396,7 +390,7 @@ bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
 	smp_rmb(); // Order *vp read and ->dynticks re-read.
 
 	// If still in the same extended quiescent state, we are good!
-	return snap == atomic_read(&rdp->dynticks);
+	return snap == ct_dynticks_cpu(cpu);
 }
 
 /*
@@ -620,6 +614,7 @@ EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
 static noinstr void rcu_eqs_enter(bool user)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
 	WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
@@ -633,12 +628,12 @@ static noinstr void rcu_eqs_enter(bool user)
 
 	lockdep_assert_irqs_disabled();
 	instrumentation_begin();
-	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks));
+	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, ct_dynticks());
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	rcu_preempt_deferred_qs(current);
 
 	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
-	instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
 
 	instrumentation_end();
 	WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
@@ -740,7 +735,7 @@ noinstr void rcu_user_enter(void)
  * rcu_nmi_exit - inform RCU of exit from NMI context
  *
  * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting
+ * RCU-idle period, update ct->dynticks and rdp->dynticks_nmi_nesting
  * to let the RCU grace-period handling know that the CPU is back to
  * being RCU-idle.
  *
@@ -749,6 +744,7 @@ noinstr void rcu_user_enter(void)
  */
 noinstr void rcu_nmi_exit(void)
 {
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
 	instrumentation_begin();
@@ -766,7 +762,7 @@ noinstr void rcu_nmi_exit(void)
 	 */
 	if (rdp->dynticks_nmi_nesting != 1) {
 		trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
-				  atomic_read(&rdp->dynticks));
+				  ct_dynticks());
 		WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
 			   rdp->dynticks_nmi_nesting - 2);
 		instrumentation_end();
@@ -774,11 +770,11 @@ noinstr void rcu_nmi_exit(void)
 	}
 
 	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
-	trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks));
+	trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, ct_dynticks());
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
 
 	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
-	instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
 	instrumentation_end();
 
 	// RCU is watching here ...
@@ -817,6 +813,7 @@ void rcu_irq_exit_check_preempt(void)
  */
 static void noinstr rcu_eqs_exit(bool user)
 {
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 	struct rcu_data *rdp;
 	long oldval;
 
@@ -836,9 +833,9 @@ static void noinstr rcu_eqs_exit(bool user)
 	instrumentation_begin();
 
 	// instrumentation for the noinstr rcu_dynticks_eqs_exit()
-	instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
 
-	trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks));
+	trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, ct_dynticks());
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	WRITE_ONCE(rdp->dynticks_nesting, 1);
 	WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
@@ -948,7 +945,7 @@ void __rcu_irq_enter_check_tick(void)
 /**
  * rcu_nmi_enter - inform RCU of entry to NMI context
  *
- * If the CPU was idle from RCU's viewpoint, update rdp->dynticks and
+ * If the CPU was idle from RCU's viewpoint, update ct->dynticks and
  * rdp->dynticks_nmi_nesting to let the RCU grace-period handling know
  * that the CPU is active.  This implementation permits nested NMIs, as
  * long as the nesting level does not overflow an int.  (You will probably
@@ -961,6 +958,7 @@ noinstr void rcu_nmi_enter(void)
 {
 	long incby = 2;
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
 	/* Complain about underflow. */
 	WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0);
@@ -984,9 +982,9 @@ noinstr void rcu_nmi_enter(void)
 
 		instrumentation_begin();
 		// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
-		instrument_atomic_read(&rdp->dynticks, sizeof(rdp->dynticks));
+		instrument_atomic_read(&ct->dynticks, sizeof(ct->dynticks));
 		// instrumentation for the noinstr rcu_dynticks_eqs_exit()
-		instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
+		instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
 
 		incby = 1;
 	} else if (!in_nmi()) {
@@ -998,7 +996,7 @@ noinstr void rcu_nmi_enter(void)
 
 	trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
 			  rdp->dynticks_nmi_nesting,
-			  rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks));
+			  rdp->dynticks_nmi_nesting + incby, ct_dynticks());
 	instrumentation_end();
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
 		   rdp->dynticks_nmi_nesting + incby);
@@ -1142,7 +1140,7 @@ static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp)
  */
 static int dyntick_save_progress_counter(struct rcu_data *rdp)
 {
-	rdp->dynticks_snap = rcu_dynticks_snap(rdp);
+	rdp->dynticks_snap = rcu_dynticks_snap(rdp->cpu);
 	if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) {
 		trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
 		rcu_gpnum_ovf(rdp->mynode, rdp);
@@ -4237,7 +4235,7 @@ rcu_boot_init_percpu_data(int cpu)
 	rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
 	INIT_WORK(&rdp->strict_work, strict_work_handler);
 	WARN_ON_ONCE(rdp->dynticks_nesting != 1);
-	WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)));
+	WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)));
 	rdp->barrier_seq_snap = rcu_state.barrier_sequence;
 	rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
 	rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 996387962de3..55a6b2191d26 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -193,7 +193,6 @@ struct rcu_data {
 	int dynticks_snap;		/* Per-GP tracking for dynticks. */
 	long dynticks_nesting;		/* Track process nesting level. */
 	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
-	atomic_t dynticks;		/* Even value for idle, else odd. */
 	bool rcu_need_heavy_qs;		/* GP old, so heavy quiescent state! */
 	bool rcu_urgent_qs;		/* GP old need light quiescent state. */
 	bool rcu_forced_tick;		/* Forced tick to provide QS. */
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index f05a15b11fa0..0374bc15ae99 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -358,7 +358,7 @@ static void __sync_rcu_exp_select_node_cpus(struct rcu_exp_work *rewp)
 		    !(rnp->qsmaskinitnext & mask)) {
 			mask_ofl_test |= mask;
 		} else {
-			snap = rcu_dynticks_snap(rdp);
+			snap = rcu_dynticks_snap(cpu);
 			if (rcu_dynticks_in_eqs(snap))
 				mask_ofl_test |= mask;
 			else
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 0a25a4ea6eef..05f5d7e820d0 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -463,7 +463,7 @@ static void print_cpu_stall_info(int cpu)
 	}
 	delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq);
 	falsepositive = rcu_is_gp_kthread_starving(NULL) &&
-			rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp));
+			rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
 	rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j);
 	if (rcuc_starved)
 		sprintf(buf, " rcuc=%ld jiffies(starved)", j);
@@ -476,7 +476,7 @@ static void print_cpu_stall_info(int cpu)
 			rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :
 				"!."[!delta],
 	       ticks_value, ticks_title,
-	       rcu_dynticks_snap(rdp) & 0xfff,
+	       rcu_dynticks_snap(cpu) & 0xfff,
 	       rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
 	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
 	       data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
-- 
2.25.1

[PATCH 15/21] rcu/context_tracking: Move dynticks_nesting to context tracking

[Frederic Weisbecker]

The RCU eqs tracking is going to be performed by the context tracking
subsystem. The related nesting counters thus need to be moved to the
context tracking structure.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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>
---
 include/linux/context_tracking_state.h | 12 ++++++++++
 kernel/context_tracking.c              |  1 +
 kernel/rcu/tree.c                      | 31 +++++++++++++-------------
 kernel/rcu/tree.h                      |  1 -
 kernel/rcu/tree_stall.h                |  2 +-
 5 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 014dc431521b..cd3a09fb0aea 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -24,6 +24,7 @@ struct context_tracking {
 	} state;
 #endif
 	atomic_t dynticks;		/* Even value for idle, else odd. */
+	long dynticks_nesting;		/* Track process nesting level. */
 };
 
 #ifdef CONFIG_CONTEXT_TRACKING
@@ -45,6 +46,17 @@ static __always_inline int ct_dynticks_cpu_acquire(int cpu)
 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
 	return atomic_read_acquire(&ct->state);
 }
+
+static __always_inline long ct_dynticks_nesting(void)
+{
+	return __this_cpu_read(context_tracking.dynticks_nesting);
+}
+
+static __always_inline long ct_dynticks_nesting_cpu(int cpu)
+{
+	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
+	return ct->dynticks_nesting;
+}
 #endif
 
 #ifdef CONFIG_CONTEXT_TRACKING_USER
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 20be30c24723..ae86fab4eab5 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -250,6 +250,7 @@ void __init context_tracking_init(void)
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_USER */
 
 DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
+		.dynticks_nesting = 1,
 		.dynticks = ATOMIC_INIT(1),
 };
 EXPORT_SYMBOL_GPL(context_tracking);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7667186731e3..826946b39943 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -75,7 +75,6 @@
 /* Data structures. */
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
-	.dynticks_nesting = 1,
 	.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
 #ifdef CONFIG_RCU_NOCB_CPU
 	.cblist.flags = SEGCBLIST_RCU_CORE,
@@ -436,7 +435,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 	lockdep_assert_irqs_disabled();
 
 	/* Check for counter underflows */
-	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
+	RCU_LOCKDEP_WARN(ct_dynticks_nesting() < 0,
 			 "RCU dynticks_nesting counter underflow!");
 	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
 			 "RCU dynticks_nmi_nesting counter underflow/zero!");
@@ -452,7 +451,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 	WARN_ON_ONCE(!nesting && !is_idle_task(current));
 
 	/* Does CPU appear to be idle from an RCU standpoint? */
-	return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
+	return ct_dynticks_nesting() == 0;
 }
 
 #define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
@@ -619,16 +618,16 @@ static noinstr void rcu_eqs_enter(bool user)
 	WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
-		     rdp->dynticks_nesting == 0);
-	if (rdp->dynticks_nesting != 1) {
+		     ct_dynticks_nesting() == 0);
+	if (ct_dynticks_nesting() != 1) {
 		// RCU will still be watching, so just do accounting and leave.
-		rdp->dynticks_nesting--;
+		ct->dynticks_nesting--;
 		return;
 	}
 
 	lockdep_assert_irqs_disabled();
 	instrumentation_begin();
-	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, ct_dynticks());
+	trace_rcu_dyntick(TPS("Start"), ct_dynticks_nesting(), 0, ct_dynticks());
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	rcu_preempt_deferred_qs(current);
 
@@ -636,7 +635,7 @@ static noinstr void rcu_eqs_enter(bool user)
 	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
 
 	instrumentation_end();
-	WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
+	WRITE_ONCE(ct->dynticks_nesting, 0); /* Avoid irq-access tearing. */
 	// RCU is watching here ...
 	rcu_dynticks_eqs_enter();
 	// ... but is no longer watching here.
@@ -793,7 +792,7 @@ void rcu_irq_exit_check_preempt(void)
 {
 	lockdep_assert_irqs_disabled();
 
-	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0,
+	RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
 			 "RCU dynticks_nesting counter underflow/zero!");
 	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
 			 DYNTICK_IRQ_NONIDLE,
@@ -819,11 +818,11 @@ static void noinstr rcu_eqs_exit(bool user)
 
 	lockdep_assert_irqs_disabled();
 	rdp = this_cpu_ptr(&rcu_data);
-	oldval = rdp->dynticks_nesting;
+	oldval = ct_dynticks_nesting();
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
 	if (oldval) {
 		// RCU was already watching, so just do accounting and leave.
-		rdp->dynticks_nesting++;
+		ct->dynticks_nesting++;
 		return;
 	}
 	rcu_dynticks_task_exit();
@@ -835,9 +834,9 @@ static void noinstr rcu_eqs_exit(bool user)
 	// instrumentation for the noinstr rcu_dynticks_eqs_exit()
 	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
 
-	trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, ct_dynticks());
+	trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
-	WRITE_ONCE(rdp->dynticks_nesting, 1);
+	WRITE_ONCE(ct->dynticks_nesting, 1);
 	WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
 	instrumentation_end();
@@ -4229,12 +4228,13 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
 static void __init
 rcu_boot_init_percpu_data(int cpu)
 {
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 
 	/* Set up local state, ensuring consistent view of global state. */
 	rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
 	INIT_WORK(&rdp->strict_work, strict_work_handler);
-	WARN_ON_ONCE(rdp->dynticks_nesting != 1);
+	WARN_ON_ONCE(ct->dynticks_nesting != 1);
 	WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)));
 	rdp->barrier_seq_snap = rcu_state.barrier_sequence;
 	rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
@@ -4259,6 +4259,7 @@ rcu_boot_init_percpu_data(int cpu)
 int rcutree_prepare_cpu(unsigned int cpu)
 {
 	unsigned long flags;
+	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
 	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 	struct rcu_node *rnp = rcu_get_root();
 
@@ -4267,7 +4268,7 @@ int rcutree_prepare_cpu(unsigned int cpu)
 	rdp->qlen_last_fqs_check = 0;
 	rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
 	rdp->blimit = blimit;
-	rdp->dynticks_nesting = 1;	/* CPU not up, no tearing. */
+	ct->dynticks_nesting = 1;	/* CPU not up, no tearing. */
 	raw_spin_unlock_rcu_node(rnp);		/* irqs remain disabled. */
 
 	/*
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 55a6b2191d26..26400b511c5b 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -191,7 +191,6 @@ struct rcu_data {
 
 	/* 3) dynticks interface. */
 	int dynticks_snap;		/* Per-GP tracking for dynticks. */
-	long dynticks_nesting;		/* Track process nesting level. */
 	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
 	bool rcu_need_heavy_qs;		/* GP old, so heavy quiescent state! */
 	bool rcu_urgent_qs;		/* GP old need light quiescent state. */
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 05f5d7e820d0..0235c03c8642 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -477,7 +477,7 @@ static void print_cpu_stall_info(int cpu)
 				"!."[!delta],
 	       ticks_value, ticks_title,
 	       rcu_dynticks_snap(cpu) & 0xfff,
-	       rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
+	       ct_dynticks_nesting_cpu(cpu), rdp->dynticks_nmi_nesting,
 	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
 	       data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
 	       rcuc_starved ? buf : "",
-- 
2.25.1

[PATCH 16/21] rcu/context_tracking: Move dynticks_nmi_nesting to context tracking

[Frederic Weisbecker]

The RCU eqs tracking is going to be performed by the context tracking
subsystem. The related nesting counters thus need to be moved to the
context tracking structure.

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>
---
 include/linux/context_tracking_state.h | 15 ++++++++
 kernel/context_tracking.c              |  1 +
 kernel/rcu/rcu.h                       |  4 ---
 kernel/rcu/tree.c                      | 48 +++++++++++---------------
 kernel/rcu/tree.h                      |  1 -
 kernel/rcu/tree_stall.h                |  2 +-
 6 files changed, 38 insertions(+), 33 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index cd3a09fb0aea..ded257130987 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -6,6 +6,9 @@
 #include <linux/static_key.h>
 #include <linux/context_tracking_irq.h>
 
+/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
+#define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
+
 struct context_tracking {
 #ifdef CONFIG_CONTEXT_TRACKING_USER
 	/*
@@ -25,6 +28,7 @@ struct context_tracking {
 #endif
 	atomic_t dynticks;		/* Even value for idle, else odd. */
 	long dynticks_nesting;		/* Track process nesting level. */
+	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
 };
 
 #ifdef CONFIG_CONTEXT_TRACKING
@@ -57,6 +61,17 @@ static __always_inline long ct_dynticks_nesting_cpu(int cpu)
 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
 	return ct->dynticks_nesting;
 }
+
+static __always_inline long ct_dynticks_nmi_nesting(void)
+{
+	return __this_cpu_read(context_tracking.dynticks_nmi_nesting);
+}
+
+static __always_inline long ct_dynticks_nmi_nesting_cpu(int cpu)
+{
+	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
+	return ct->dynticks_nmi_nesting;
+}
 #endif
 
 #ifdef CONFIG_CONTEXT_TRACKING_USER
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index ae86fab4eab5..14f04c521573 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -250,6 +250,7 @@ void __init context_tracking_init(void)
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_USER */
 
 DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
+		.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
 		.dynticks_nesting = 1,
 		.dynticks = ATOMIC_INIT(1),
 };
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 15b96f990774..f86584fe90ba 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -12,10 +12,6 @@
 
 #include <trace/events/rcu.h>
 
-/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
-#define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
-
-
 /*
  * Grace-period counter management.
  */
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 826946b39943..7b1404db3c17 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -75,7 +75,6 @@
 /* Data structures. */
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
-	.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
 #ifdef CONFIG_RCU_NOCB_CPU
 	.cblist.flags = SEGCBLIST_RCU_CORE,
 #endif
@@ -437,11 +436,11 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 	/* Check for counter underflows */
 	RCU_LOCKDEP_WARN(ct_dynticks_nesting() < 0,
 			 "RCU dynticks_nesting counter underflow!");
-	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
+	RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() <= 0,
 			 "RCU dynticks_nmi_nesting counter underflow/zero!");
 
 	/* Are we at first interrupt nesting level? */
-	nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting);
+	nesting = ct_dynticks_nmi_nesting();
 	if (nesting > 1)
 		return false;
 
@@ -612,11 +611,10 @@ EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
  */
 static noinstr void rcu_eqs_enter(bool user)
 {
-	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
-	WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
-	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting() != DYNTICK_IRQ_NONIDLE);
+	WRITE_ONCE(ct->dynticks_nmi_nesting, 0);
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
 		     ct_dynticks_nesting() == 0);
 	if (ct_dynticks_nesting() != 1) {
@@ -734,7 +732,7 @@ noinstr void rcu_user_enter(void)
  * rcu_nmi_exit - inform RCU of exit from NMI context
  *
  * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update ct->dynticks and rdp->dynticks_nmi_nesting
+ * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
  * to let the RCU grace-period handling know that the CPU is back to
  * being RCU-idle.
  *
@@ -744,7 +742,6 @@ noinstr void rcu_user_enter(void)
 noinstr void rcu_nmi_exit(void)
 {
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
-	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
 	instrumentation_begin();
 	/*
@@ -752,25 +749,25 @@ noinstr void rcu_nmi_exit(void)
 	 * (We are exiting an NMI handler, so RCU better be paying attention
 	 * to us!)
 	 */
-	WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0);
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting() <= 0);
 	WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
 
 	/*
 	 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
 	 * leave it in non-RCU-idle state.
 	 */
-	if (rdp->dynticks_nmi_nesting != 1) {
-		trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
+	if (ct_dynticks_nmi_nesting() != 1) {
+		trace_rcu_dyntick(TPS("--="), ct_dynticks_nmi_nesting(), ct_dynticks_nmi_nesting() - 2,
 				  ct_dynticks());
-		WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
-			   rdp->dynticks_nmi_nesting - 2);
+		WRITE_ONCE(ct->dynticks_nmi_nesting, /* No store tearing. */
+			   ct_dynticks_nmi_nesting() - 2);
 		instrumentation_end();
 		return;
 	}
 
 	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
-	trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, ct_dynticks());
-	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
+	trace_rcu_dyntick(TPS("Startirq"), ct_dynticks_nmi_nesting(), 0, ct_dynticks());
+	WRITE_ONCE(ct->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
 
 	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
 	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
@@ -794,7 +791,7 @@ void rcu_irq_exit_check_preempt(void)
 
 	RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
 			 "RCU dynticks_nesting counter underflow/zero!");
-	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
+	RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() !=
 			 DYNTICK_IRQ_NONIDLE,
 			 "Bad RCU  dynticks_nmi_nesting counter\n");
 	RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
@@ -813,11 +810,9 @@ void rcu_irq_exit_check_preempt(void)
 static void noinstr rcu_eqs_exit(bool user)
 {
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
-	struct rcu_data *rdp;
 	long oldval;
 
 	lockdep_assert_irqs_disabled();
-	rdp = this_cpu_ptr(&rcu_data);
 	oldval = ct_dynticks_nesting();
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
 	if (oldval) {
@@ -837,8 +832,8 @@ static void noinstr rcu_eqs_exit(bool user)
 	trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	WRITE_ONCE(ct->dynticks_nesting, 1);
-	WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
-	WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting());
+	WRITE_ONCE(ct->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
 	instrumentation_end();
 }
 
@@ -945,7 +940,7 @@ void __rcu_irq_enter_check_tick(void)
  * rcu_nmi_enter - inform RCU of entry to NMI context
  *
  * If the CPU was idle from RCU's viewpoint, update ct->dynticks and
- * rdp->dynticks_nmi_nesting to let the RCU grace-period handling know
+ * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
  * that the CPU is active.  This implementation permits nested NMIs, as
  * long as the nesting level does not overflow an int.  (You will probably
  * run out of stack space first.)
@@ -956,11 +951,10 @@ void __rcu_irq_enter_check_tick(void)
 noinstr void rcu_nmi_enter(void)
 {
 	long incby = 2;
-	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
 	/* Complain about underflow. */
-	WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0);
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting() < 0);
 
 	/*
 	 * If idle from RCU viewpoint, atomically increment ->dynticks
@@ -994,11 +988,11 @@ noinstr void rcu_nmi_enter(void)
 	}
 
 	trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
-			  rdp->dynticks_nmi_nesting,
-			  rdp->dynticks_nmi_nesting + incby, ct_dynticks());
+			  ct_dynticks_nmi_nesting(),
+			  ct_dynticks_nmi_nesting() + incby, ct_dynticks());
 	instrumentation_end();
-	WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
-		   rdp->dynticks_nmi_nesting + incby);
+	WRITE_ONCE(ct->dynticks_nmi_nesting, /* Prevent store tearing. */
+		   ct_dynticks_nmi_nesting() + incby);
 	barrier();
 }
 
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 26400b511c5b..11f3e0581782 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -191,7 +191,6 @@ struct rcu_data {
 
 	/* 3) dynticks interface. */
 	int dynticks_snap;		/* Per-GP tracking for dynticks. */
-	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
 	bool rcu_need_heavy_qs;		/* GP old, so heavy quiescent state! */
 	bool rcu_urgent_qs;		/* GP old need light quiescent state. */
 	bool rcu_forced_tick;		/* Forced tick to provide QS. */
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 0235c03c8642..933445d826f1 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -477,7 +477,7 @@ static void print_cpu_stall_info(int cpu)
 				"!."[!delta],
 	       ticks_value, ticks_title,
 	       rcu_dynticks_snap(cpu) & 0xfff,
-	       ct_dynticks_nesting_cpu(cpu), rdp->dynticks_nmi_nesting,
+	       ct_dynticks_nesting_cpu(cpu), ct_dynticks_nmi_nesting_cpu(cpu),
 	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
 	       data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
 	       rcuc_starved ? buf : "",
-- 
2.25.1

[PATCH 17/21] rcu/context-tracking: Move deferred nocb resched to context tracking

[Frederic Weisbecker]

To prepare for migrating the RCU eqs accounting code to context tracking,
split the last-resort deferred nocb resched from rcu_user_enter() and
move it into a separate call from context tracking.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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>
---
 include/linux/rcutree.h   |  6 ++++++
 kernel/context_tracking.c |  8 ++++++++
 kernel/rcu/tree.c         | 15 ++-------------
 3 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index cafe3fbf4272..6294271f1615 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -76,4 +76,10 @@ int rcutree_dead_cpu(unsigned int cpu);
 int rcutree_dying_cpu(unsigned int cpu);
 void rcu_cpu_starting(unsigned int cpu);
 
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
+void rcu_irq_work_resched(void);
+#else
+static inline void rcu_irq_work_resched(void) { }
+#endif
+
 #endif /* __LINUX_RCUTREE_H */
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 14f04c521573..4ca4aeadad06 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -60,6 +60,8 @@ static __always_inline void context_tracking_recursion_exit(void)
  */
 void noinstr __ct_user_enter(enum ctx_state state)
 {
+	lockdep_assert_irqs_disabled();
+
 	/* Kernel threads aren't supposed to go to userspace */
 	WARN_ON_ONCE(!current->mm);
 
@@ -81,6 +83,12 @@ void noinstr __ct_user_enter(enum ctx_state state)
 				vtime_user_enter(current);
 				instrumentation_end();
 			}
+			/*
+			 * Other than generic entry implementation, we may be past the last
+			 * rescheduling opportunity in the entry code. Trigger a self IPI
+			 * that will fire and reschedule once we resume in user/guest mode.
+			 */
+			rcu_irq_work_resched();
 			rcu_user_enter();
 		}
 		/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7b1404db3c17..7d1a3e73ff25 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -681,7 +681,7 @@ static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) =
  * last resort is to fire a local irq_work that will trigger a reschedule once IRQs
  * get re-enabled again.
  */
-noinstr static void rcu_irq_work_resched(void)
+noinstr void rcu_irq_work_resched(void)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
@@ -697,10 +697,7 @@ noinstr static void rcu_irq_work_resched(void)
 	}
 	instrumentation_end();
 }
-
-#else
-static inline void rcu_irq_work_resched(void) { }
-#endif
+#endif /* #if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK) */
 
 /**
  * rcu_user_enter - inform RCU that we are resuming userspace.
@@ -715,14 +712,6 @@ static inline void rcu_irq_work_resched(void) { }
  */
 noinstr void rcu_user_enter(void)
 {
-	lockdep_assert_irqs_disabled();
-
-	/*
-	 * Other than generic entry implementation, we may be past the last
-	 * rescheduling opportunity in the entry code. Trigger a self IPI
-	 * that will fire and reschedule once we resume in user/guest mode.
-	 */
-	rcu_irq_work_resched();
 	rcu_eqs_enter(true);
 }
 
-- 
2.25.1

[PATCH 18/21] rcu/context-tracking: Move RCU-dynticks internal functions to context_tracking

[Frederic Weisbecker]

Move the core RCU eqs/dynticks functions to context tracking so that
we can later merge all that code within context tracking.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@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>
---
 include/linux/context_tracking.h |  20 ++
 include/linux/rcutree.h          |   3 +
 kernel/context_tracking.c        | 342 +++++++++++++++++++++++++++++++
 kernel/rcu/tree.c                | 328 +----------------------------
 kernel/rcu/tree.h                |   5 -
 kernel/rcu/tree_plugin.h         |  38 +---
 6 files changed, 370 insertions(+), 366 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 27afb75f2650..cad8aecb7321 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -122,6 +122,26 @@ static inline void context_tracking_init(void) { }
 #ifdef CONFIG_CONTEXT_TRACKING
 extern void ct_idle_enter(void);
 extern void ct_idle_exit(void);
+
+/*
+ * Is the current CPU in an extended quiescent state?
+ *
+ * No ordering, as we are sampling CPU-local information.
+ */
+static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
+{
+	return !(arch_atomic_read(this_cpu_ptr(&context_tracking.dynticks)) & 0x1);
+}
+
+/*
+ * Increment the current CPU's context_tracking structure's ->dynticks field
+ * with ordering.  Return the new value.
+ */
+static __always_inline unsigned long rcu_dynticks_inc(int incby)
+{
+	return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.dynticks));
+}
+
 #else
 static inline void ct_idle_enter(void) { }
 static inline void ct_idle_exit(void) { }
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 6294271f1615..d9e8e6233c47 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -57,6 +57,9 @@ void rcu_irq_exit_check_preempt(void);
 static inline void rcu_irq_exit_check_preempt(void) { }
 #endif
 
+struct task_struct;
+void rcu_preempt_deferred_qs(struct task_struct *t);
+
 void exit_rcu(void);
 
 void rcu_scheduler_starting(void);
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 4ca4aeadad06..279fb5875dd8 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -21,6 +21,348 @@
 #include <linux/hardirq.h>
 #include <linux/export.h>
 #include <linux/kprobes.h>
+#include <trace/events/rcu.h>
+
+#define TPS(x)  tracepoint_string(x)
+
+/* Record the current task on dyntick-idle entry. */
+static __always_inline void rcu_dynticks_task_enter(void)
+{
+#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
+	WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id());
+#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
+}
+
+/* Record no current task on dyntick-idle exit. */
+static __always_inline void rcu_dynticks_task_exit(void)
+{
+#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
+	WRITE_ONCE(current->rcu_tasks_idle_cpu, -1);
+#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
+}
+
+/* Turn on heavyweight RCU tasks trace readers on idle/user entry. */
+static __always_inline void rcu_dynticks_task_trace_enter(void)
+{
+#ifdef CONFIG_TASKS_TRACE_RCU
+	if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
+		current->trc_reader_special.b.need_mb = true;
+#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
+}
+
+/* Turn off heavyweight RCU tasks trace readers on idle/user exit. */
+static __always_inline void rcu_dynticks_task_trace_exit(void)
+{
+#ifdef CONFIG_TASKS_TRACE_RCU
+	if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
+		current->trc_reader_special.b.need_mb = false;
+#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
+}
+
+/*
+ * Record entry into an extended quiescent state.  This is only to be
+ * called when not already in an extended quiescent state, that is,
+ * RCU is watching prior to the call to this function and is no longer
+ * watching upon return.
+ */
+static noinstr void rcu_dynticks_eqs_enter(void)
+{
+	int seq;
+
+	/*
+	 * CPUs seeing atomic_add_return() must see prior RCU read-side
+	 * critical sections, and we also must force ordering with the
+	 * next idle sojourn.
+	 */
+	rcu_dynticks_task_trace_enter();  // Before ->dynticks update!
+	seq = rcu_dynticks_inc(1);
+	// RCU is no longer watching.  Better be in extended quiescent state!
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & 0x1));
+}
+
+/*
+ * Record exit from an extended quiescent state.  This is only to be
+ * called from an extended quiescent state, that is, RCU is not watching
+ * prior to the call to this function and is watching upon return.
+ */
+static noinstr void rcu_dynticks_eqs_exit(void)
+{
+	int seq;
+
+	/*
+	 * CPUs seeing atomic_add_return() must see prior idle sojourns,
+	 * and we also must force ordering with the next RCU read-side
+	 * critical section.
+	 */
+	seq = rcu_dynticks_inc(1);
+	// RCU is now watching.  Better not be in an extended quiescent state!
+	rcu_dynticks_task_trace_exit();  // After ->dynticks update!
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & 0x1));
+}
+
+/*
+ * Enter an RCU extended quiescent state, which can be either the
+ * idle loop or adaptive-tickless usermode execution.
+ *
+ * We crowbar the ->dynticks_nmi_nesting field to zero to allow for
+ * the possibility of usermode upcalls having messed up our count
+ * of interrupt nesting level during the prior busy period.
+ */
+static noinstr void rcu_eqs_enter(bool user)
+{
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
+
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting() != DYNTICK_IRQ_NONIDLE);
+	WRITE_ONCE(ct->dynticks_nmi_nesting, 0);
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
+		     ct_dynticks_nesting() == 0);
+	if (ct_dynticks_nesting() != 1) {
+		// RCU will still be watching, so just do accounting and leave.
+		ct->dynticks_nesting--;
+		return;
+	}
+
+	lockdep_assert_irqs_disabled();
+	instrumentation_begin();
+	trace_rcu_dyntick(TPS("Start"), ct_dynticks_nesting(), 0, ct_dynticks());
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
+	rcu_preempt_deferred_qs(current);
+
+	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
+	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+
+	instrumentation_end();
+	WRITE_ONCE(ct->dynticks_nesting, 0); /* Avoid irq-access tearing. */
+	// RCU is watching here ...
+	rcu_dynticks_eqs_enter();
+	// ... but is no longer watching here.
+	rcu_dynticks_task_enter();
+}
+
+/**
+ * rcu_idle_enter - inform RCU that current CPU is entering idle
+ *
+ * Enter idle mode, in other words, -leave- the mode in which RCU
+ * read-side critical sections can occur.  (Though RCU read-side
+ * critical sections can occur in irq handlers in idle, a possibility
+ * handled by irq_enter() and irq_exit().)
+ *
+ * If you add or remove a call to rcu_idle_enter(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
+noinstr void rcu_idle_enter(void)
+{
+	lockdep_assert_irqs_disabled();
+	rcu_eqs_enter(false);
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+/**
+ * rcu_user_enter - inform RCU that we are resuming userspace.
+ *
+ * Enter RCU idle mode right before resuming userspace.  No use of RCU
+ * is permitted between this call and rcu_user_exit(). This way the
+ * CPU doesn't need to maintain the tick for RCU maintenance purposes
+ * when the CPU runs in userspace.
+ *
+ * If you add or remove a call to rcu_user_enter(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
+noinstr void rcu_user_enter(void)
+{
+	rcu_eqs_enter(true);
+}
+#endif /* CONFIG_NO_HZ_FULL */
+
+/**
+ * rcu_nmi_exit - inform RCU of exit from NMI context
+ *
+ * If we are returning from the outermost NMI handler that interrupted an
+ * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
+ * to let the RCU grace-period handling know that the CPU is back to
+ * being RCU-idle.
+ *
+ * If you add or remove a call to rcu_nmi_exit(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ */
+noinstr void rcu_nmi_exit(void)
+{
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
+
+	instrumentation_begin();
+	/*
+	 * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
+	 * (We are exiting an NMI handler, so RCU better be paying attention
+	 * to us!)
+	 */
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting() <= 0);
+	WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
+
+	/*
+	 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
+	 * leave it in non-RCU-idle state.
+	 */
+	if (ct_dynticks_nmi_nesting() != 1) {
+		trace_rcu_dyntick(TPS("--="), ct_dynticks_nmi_nesting(), ct_dynticks_nmi_nesting() - 2,
+				  ct_dynticks());
+		WRITE_ONCE(ct->dynticks_nmi_nesting, /* No store tearing. */
+			   ct_dynticks_nmi_nesting() - 2);
+		instrumentation_end();
+		return;
+	}
+
+	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
+	trace_rcu_dyntick(TPS("Startirq"), ct_dynticks_nmi_nesting(), 0, ct_dynticks());
+	WRITE_ONCE(ct->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
+
+	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
+	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+	instrumentation_end();
+
+	// RCU is watching here ...
+	rcu_dynticks_eqs_enter();
+	// ... but is no longer watching here.
+
+	if (!in_nmi())
+		rcu_dynticks_task_enter();
+}
+
+/*
+ * Exit an RCU extended quiescent state, which can be either the
+ * idle loop or adaptive-tickless usermode execution.
+ *
+ * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to
+ * allow for the possibility of usermode upcalls messing up our count of
+ * interrupt nesting level during the busy period that is just now starting.
+ */
+static void noinstr rcu_eqs_exit(bool user)
+{
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
+	long oldval;
+
+	lockdep_assert_irqs_disabled();
+	oldval = ct_dynticks_nesting();
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
+	if (oldval) {
+		// RCU was already watching, so just do accounting and leave.
+		ct->dynticks_nesting++;
+		return;
+	}
+	rcu_dynticks_task_exit();
+	// RCU is not watching here ...
+	rcu_dynticks_eqs_exit();
+	// ... but is watching here.
+	instrumentation_begin();
+
+	// instrumentation for the noinstr rcu_dynticks_eqs_exit()
+	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+
+	trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
+	WRITE_ONCE(ct->dynticks_nesting, 1);
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting());
+	WRITE_ONCE(ct->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
+	instrumentation_end();
+}
+
+/**
+ * rcu_idle_exit - inform RCU that current CPU is leaving idle
+ *
+ * Exit idle mode, in other words, -enter- the mode in which RCU
+ * read-side critical sections can occur.
+ *
+ * If you add or remove a call to rcu_idle_exit(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_save() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
+ */
+void rcu_idle_exit(void)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	rcu_eqs_exit(false);
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
+
+#ifdef CONFIG_NO_HZ_FULL
+/**
+ * rcu_user_exit - inform RCU that we are exiting userspace.
+ *
+ * Exit RCU idle mode while entering the kernel because it can
+ * run a RCU read side critical section anytime.
+ *
+ * If you add or remove a call to rcu_user_exit(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
+void noinstr rcu_user_exit(void)
+{
+	rcu_eqs_exit(true);
+}
+#endif /* ifdef CONFIG_NO_HZ_FULL */
+
+/**
+ * rcu_nmi_enter - inform RCU of entry to NMI context
+ *
+ * If the CPU was idle from RCU's viewpoint, update ct->dynticks and
+ * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
+ * that the CPU is active.  This implementation permits nested NMIs, as
+ * long as the nesting level does not overflow an int.  (You will probably
+ * run out of stack space first.)
+ *
+ * If you add or remove a call to rcu_nmi_enter(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ */
+noinstr void rcu_nmi_enter(void)
+{
+	long incby = 2;
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
+
+	/* Complain about underflow. */
+	WARN_ON_ONCE(ct_dynticks_nmi_nesting() < 0);
+
+	/*
+	 * If idle from RCU viewpoint, atomically increment ->dynticks
+	 * to mark non-idle and increment ->dynticks_nmi_nesting by one.
+	 * Otherwise, increment ->dynticks_nmi_nesting by two.  This means
+	 * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
+	 * to be in the outermost NMI handler that interrupted an RCU-idle
+	 * period (observation due to Andy Lutomirski).
+	 */
+	if (rcu_dynticks_curr_cpu_in_eqs()) {
+
+		if (!in_nmi())
+			rcu_dynticks_task_exit();
+
+		// RCU is not watching here ...
+		rcu_dynticks_eqs_exit();
+		// ... but is watching here.
+
+		instrumentation_begin();
+		// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
+		instrument_atomic_read(&ct->dynticks, sizeof(ct->dynticks));
+		// instrumentation for the noinstr rcu_dynticks_eqs_exit()
+		instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+
+		incby = 1;
+	} else if (!in_nmi()) {
+		instrumentation_begin();
+		rcu_irq_enter_check_tick();
+	} else  {
+		instrumentation_begin();
+	}
+
+	trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
+			  ct_dynticks_nmi_nesting(),
+			  ct_dynticks_nmi_nesting() + incby, ct_dynticks());
+	instrumentation_end();
+	WRITE_ONCE(ct->dynticks_nmi_nesting, /* Prevent store tearing. */
+		   ct_dynticks_nmi_nesting() + incby);
+	barrier();
+}
 
 #ifdef CONFIG_CONTEXT_TRACKING_USER
 
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7d1a3e73ff25..16d601512da7 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -62,6 +62,7 @@
 #include <linux/vmalloc.h>
 #include <linux/mm.h>
 #include <linux/kasan.h>
+#include <linux/context_tracking.h>
 #include "../time/tick-internal.h"
 
 #include "tree.h"
@@ -259,56 +260,6 @@ void rcu_softirq_qs(void)
 	rcu_tasks_qs(current, false);
 }
 
-/*
- * Increment the current CPU's rcu_data structure's ->dynticks field
- * with ordering.  Return the new value.
- */
-static noinline noinstr unsigned long rcu_dynticks_inc(int incby)
-{
-	return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.dynticks));
-}
-
-/*
- * Record entry into an extended quiescent state.  This is only to be
- * called when not already in an extended quiescent state, that is,
- * RCU is watching prior to the call to this function and is no longer
- * watching upon return.
- */
-static noinstr void rcu_dynticks_eqs_enter(void)
-{
-	int seq;
-
-	/*
-	 * CPUs seeing atomic_add_return() must see prior RCU read-side
-	 * critical sections, and we also must force ordering with the
-	 * next idle sojourn.
-	 */
-	rcu_dynticks_task_trace_enter();  // Before ->dynticks update!
-	seq = rcu_dynticks_inc(1);
-	// RCU is no longer watching.  Better be in extended quiescent state!
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & 0x1));
-}
-
-/*
- * Record exit from an extended quiescent state.  This is only to be
- * called from an extended quiescent state, that is, RCU is not watching
- * prior to the call to this function and is watching upon return.
- */
-static noinstr void rcu_dynticks_eqs_exit(void)
-{
-	int seq;
-
-	/*
-	 * CPUs seeing atomic_add_return() must see prior idle sojourns,
-	 * and we also must force ordering with the next RCU read-side
-	 * critical section.
-	 */
-	seq = rcu_dynticks_inc(1);
-	// RCU is now watching.  Better not be in an extended quiescent state!
-	rcu_dynticks_task_trace_exit();  // After ->dynticks update!
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & 0x1));
-}
-
 /*
  * Reset the current CPU's ->dynticks counter to indicate that the
  * newly onlined CPU is no longer in an extended quiescent state.
@@ -326,16 +277,6 @@ static void rcu_dynticks_eqs_online(void)
 	rcu_dynticks_inc(1);
 }
 
-/*
- * Is the current CPU in an extended quiescent state?
- *
- * No ordering, as we are sampling CPU-local information.
- */
-static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
-{
-	return !(arch_atomic_read(this_cpu_ptr(&context_tracking.dynticks)) & 0x1);
-}
-
 /*
  * Snapshot the ->dynticks counter with full ordering so as to allow
  * stable comparison of this counter with past and future snapshots.
@@ -601,65 +542,7 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 }
 EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
 
-/*
- * Enter an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- *
- * We crowbar the ->dynticks_nmi_nesting field to zero to allow for
- * the possibility of usermode upcalls having messed up our count
- * of interrupt nesting level during the prior busy period.
- */
-static noinstr void rcu_eqs_enter(bool user)
-{
-	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
-
-	WARN_ON_ONCE(ct_dynticks_nmi_nesting() != DYNTICK_IRQ_NONIDLE);
-	WRITE_ONCE(ct->dynticks_nmi_nesting, 0);
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
-		     ct_dynticks_nesting() == 0);
-	if (ct_dynticks_nesting() != 1) {
-		// RCU will still be watching, so just do accounting and leave.
-		ct->dynticks_nesting--;
-		return;
-	}
-
-	lockdep_assert_irqs_disabled();
-	instrumentation_begin();
-	trace_rcu_dyntick(TPS("Start"), ct_dynticks_nesting(), 0, ct_dynticks());
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
-	rcu_preempt_deferred_qs(current);
-
-	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
-	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
-
-	instrumentation_end();
-	WRITE_ONCE(ct->dynticks_nesting, 0); /* Avoid irq-access tearing. */
-	// RCU is watching here ...
-	rcu_dynticks_eqs_enter();
-	// ... but is no longer watching here.
-	rcu_dynticks_task_enter();
-}
-
-/**
- * rcu_idle_enter - inform RCU that current CPU is entering idle
- *
- * Enter idle mode, in other words, -leave- the mode in which RCU
- * read-side critical sections can occur.  (Though RCU read-side
- * critical sections can occur in irq handlers in idle, a possibility
- * handled by irq_enter() and irq_exit().)
- *
- * If you add or remove a call to rcu_idle_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_idle_enter(void)
-{
-	lockdep_assert_irqs_disabled();
-	rcu_eqs_enter(false);
-}
-
-#ifdef CONFIG_NO_HZ_FULL
-
-#if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
 /*
  * An empty function that will trigger a reschedule on
  * IRQ tail once IRQs get re-enabled on userspace/guest resume.
@@ -697,78 +580,7 @@ noinstr void rcu_irq_work_resched(void)
 	}
 	instrumentation_end();
 }
-#endif /* #if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK) */
-
-/**
- * rcu_user_enter - inform RCU that we are resuming userspace.
- *
- * Enter RCU idle mode right before resuming userspace.  No use of RCU
- * is permitted between this call and rcu_user_exit(). This way the
- * CPU doesn't need to maintain the tick for RCU maintenance purposes
- * when the CPU runs in userspace.
- *
- * If you add or remove a call to rcu_user_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_user_enter(void)
-{
-	rcu_eqs_enter(true);
-}
-
-#endif /* CONFIG_NO_HZ_FULL */
-
-/**
- * rcu_nmi_exit - inform RCU of exit from NMI context
- *
- * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
- * to let the RCU grace-period handling know that the CPU is back to
- * being RCU-idle.
- *
- * If you add or remove a call to rcu_nmi_exit(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_nmi_exit(void)
-{
-	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
-
-	instrumentation_begin();
-	/*
-	 * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
-	 * (We are exiting an NMI handler, so RCU better be paying attention
-	 * to us!)
-	 */
-	WARN_ON_ONCE(ct_dynticks_nmi_nesting() <= 0);
-	WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
-
-	/*
-	 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
-	 * leave it in non-RCU-idle state.
-	 */
-	if (ct_dynticks_nmi_nesting() != 1) {
-		trace_rcu_dyntick(TPS("--="), ct_dynticks_nmi_nesting(), ct_dynticks_nmi_nesting() - 2,
-				  ct_dynticks());
-		WRITE_ONCE(ct->dynticks_nmi_nesting, /* No store tearing. */
-			   ct_dynticks_nmi_nesting() - 2);
-		instrumentation_end();
-		return;
-	}
-
-	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
-	trace_rcu_dyntick(TPS("Startirq"), ct_dynticks_nmi_nesting(), 0, ct_dynticks());
-	WRITE_ONCE(ct->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
-
-	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
-	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
-	instrumentation_end();
-
-	// RCU is watching here ...
-	rcu_dynticks_eqs_enter();
-	// ... but is no longer watching here.
-
-	if (!in_nmi())
-		rcu_dynticks_task_enter();
-}
+#endif /* #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) */
 
 #ifdef CONFIG_PROVE_RCU
 /**
@@ -788,81 +600,7 @@ void rcu_irq_exit_check_preempt(void)
 }
 #endif /* #ifdef CONFIG_PROVE_RCU */
 
-/*
- * Exit an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- *
- * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to
- * allow for the possibility of usermode upcalls messing up our count of
- * interrupt nesting level during the busy period that is just now starting.
- */
-static void noinstr rcu_eqs_exit(bool user)
-{
-	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
-	long oldval;
-
-	lockdep_assert_irqs_disabled();
-	oldval = ct_dynticks_nesting();
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
-	if (oldval) {
-		// RCU was already watching, so just do accounting and leave.
-		ct->dynticks_nesting++;
-		return;
-	}
-	rcu_dynticks_task_exit();
-	// RCU is not watching here ...
-	rcu_dynticks_eqs_exit();
-	// ... but is watching here.
-	instrumentation_begin();
-
-	// instrumentation for the noinstr rcu_dynticks_eqs_exit()
-	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
-
-	trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
-	WRITE_ONCE(ct->dynticks_nesting, 1);
-	WARN_ON_ONCE(ct_dynticks_nmi_nesting());
-	WRITE_ONCE(ct->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
-	instrumentation_end();
-}
-
-/**
- * rcu_idle_exit - inform RCU that current CPU is leaving idle
- *
- * Exit idle mode, in other words, -enter- the mode in which RCU
- * read-side critical sections can occur.
- *
- * If you add or remove a call to rcu_idle_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- *
- * FIXME: This function should be noinstr but the below local_irq_save() is
- * unsafe because it involves illegal RCU uses through tracing and lockdep.
- * This must be fixed first.
- */
-void rcu_idle_exit(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	rcu_eqs_exit(false);
-	local_irq_restore(flags);
-}
-
 #ifdef CONFIG_NO_HZ_FULL
-/**
- * rcu_user_exit - inform RCU that we are exiting userspace.
- *
- * Exit RCU idle mode while entering the kernel because it can
- * run a RCU read side critical section anytime.
- *
- * If you add or remove a call to rcu_user_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void noinstr rcu_user_exit(void)
-{
-	rcu_eqs_exit(true);
-}
-
 /**
  * __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it.
  *
@@ -925,66 +663,6 @@ void __rcu_irq_enter_check_tick(void)
 }
 #endif /* CONFIG_NO_HZ_FULL */
 
-/**
- * rcu_nmi_enter - inform RCU of entry to NMI context
- *
- * If the CPU was idle from RCU's viewpoint, update ct->dynticks and
- * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
- * that the CPU is active.  This implementation permits nested NMIs, as
- * long as the nesting level does not overflow an int.  (You will probably
- * run out of stack space first.)
- *
- * If you add or remove a call to rcu_nmi_enter(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_nmi_enter(void)
-{
-	long incby = 2;
-	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
-
-	/* Complain about underflow. */
-	WARN_ON_ONCE(ct_dynticks_nmi_nesting() < 0);
-
-	/*
-	 * If idle from RCU viewpoint, atomically increment ->dynticks
-	 * to mark non-idle and increment ->dynticks_nmi_nesting by one.
-	 * Otherwise, increment ->dynticks_nmi_nesting by two.  This means
-	 * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
-	 * to be in the outermost NMI handler that interrupted an RCU-idle
-	 * period (observation due to Andy Lutomirski).
-	 */
-	if (rcu_dynticks_curr_cpu_in_eqs()) {
-
-		if (!in_nmi())
-			rcu_dynticks_task_exit();
-
-		// RCU is not watching here ...
-		rcu_dynticks_eqs_exit();
-		// ... but is watching here.
-
-		instrumentation_begin();
-		// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
-		instrument_atomic_read(&ct->dynticks, sizeof(ct->dynticks));
-		// instrumentation for the noinstr rcu_dynticks_eqs_exit()
-		instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
-
-		incby = 1;
-	} else if (!in_nmi()) {
-		instrumentation_begin();
-		rcu_irq_enter_check_tick();
-	} else  {
-		instrumentation_begin();
-	}
-
-	trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
-			  ct_dynticks_nmi_nesting(),
-			  ct_dynticks_nmi_nesting() + incby, ct_dynticks());
-	instrumentation_end();
-	WRITE_ONCE(ct->dynticks_nmi_nesting, /* Prevent store tearing. */
-		   ct_dynticks_nmi_nesting() + incby);
-	barrier();
-}
-
 /*
  * Check to see if any future non-offloaded RCU-related work will need
  * to be done by the current CPU, even if none need be done immediately,
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 11f3e0581782..4ed7f1bdbb0f 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -435,7 +435,6 @@ static void rcu_cpu_kthread_setup(unsigned int cpu);
 static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
 static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
-static void rcu_preempt_deferred_qs(struct task_struct *t);
 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
@@ -475,10 +474,6 @@ do {								\
 
 static void rcu_bind_gp_kthread(void);
 static bool rcu_nohz_full_cpu(void);
-static void rcu_dynticks_task_enter(void);
-static void rcu_dynticks_task_exit(void);
-static void rcu_dynticks_task_trace_enter(void);
-static void rcu_dynticks_task_trace_exit(void);
 
 /* Forward declarations for tree_stall.h */
 static void record_gp_stall_check_time(void);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 440d9e02a26e..1bb1f571285d 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -595,7 +595,7 @@ static notrace bool rcu_preempt_need_deferred_qs(struct task_struct *t)
  * evaluate safety in terms of interrupt, softirq, and preemption
  * disabling.
  */
-static notrace void rcu_preempt_deferred_qs(struct task_struct *t)
+notrace void rcu_preempt_deferred_qs(struct task_struct *t)
 {
 	unsigned long flags;
 
@@ -935,7 +935,7 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
 // period for a quiescent state from this CPU.  Note that requests from
 // tasks are handled when removing the task from the blocked-tasks list
 // below.
-static void rcu_preempt_deferred_qs(struct task_struct *t)
+void rcu_preempt_deferred_qs(struct task_struct *t)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
@@ -1290,37 +1290,3 @@ static void rcu_bind_gp_kthread(void)
 		return;
 	housekeeping_affine(current, HK_TYPE_RCU);
 }
-
-/* Record the current task on dyntick-idle entry. */
-static __always_inline void rcu_dynticks_task_enter(void)
-{
-#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
-	WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id());
-#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
-}
-
-/* Record no current task on dyntick-idle exit. */
-static __always_inline void rcu_dynticks_task_exit(void)
-{
-#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
-	WRITE_ONCE(current->rcu_tasks_idle_cpu, -1);
-#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
-}
-
-/* Turn on heavyweight RCU tasks trace readers on idle/user entry. */
-static __always_inline void rcu_dynticks_task_trace_enter(void)
-{
-#ifdef CONFIG_TASKS_TRACE_RCU
-	if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
-		current->trc_reader_special.b.need_mb = true;
-#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
-}
-
-/* Turn off heavyweight RCU tasks trace readers on idle/user exit. */
-static __always_inline void rcu_dynticks_task_trace_exit(void)
-{
-#ifdef CONFIG_TASKS_TRACE_RCU
-	if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
-		current->trc_reader_special.b.need_mb = false;
-#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
-}
-- 
2.25.1

[PATCH 19/21] rcu/context-tracking: Remove unused and/or unecessary middle functions

[Frederic Weisbecker]

Some eqs functions are now only used internally by context tracking, so
their public declarations can be removed.

Also middle functions such as rcu_user_*() and rcu_idle_*()
which now directly call to rcu_eqs_enter() and rcu_eqs_exit() can be
wiped out as well.

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 |   2 +-
 include/linux/hardirq.h         |   8 --
 include/linux/rcupdate.h        |   8 --
 include/linux/rcutiny.h         |   2 -
 include/linux/rcutree.h         |   2 -
 kernel/context_tracking.c       | 147 +++++++++++---------------------
 6 files changed, 50 insertions(+), 119 deletions(-)

diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst
index 7858c3afa1f4..bebcaef475a6 100644
--- a/Documentation/RCU/stallwarn.rst
+++ b/Documentation/RCU/stallwarn.rst
@@ -97,7 +97,7 @@ 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(), ct_idle_enter(),
+	variants of rcu_eqs_enter(true), rcu_eqs_exit(true), ct_idle_enter(),
 	ct_idle_exit(), ct_irq_enter(), or ct_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
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 345cdbe9c1b7..d57cab4d4c06 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -92,14 +92,6 @@ void irq_exit_rcu(void);
 #define arch_nmi_exit()		do { } while (0)
 #endif
 
-#ifdef CONFIG_TINY_RCU
-static inline void rcu_nmi_enter(void) { }
-static inline void rcu_nmi_exit(void) { }
-#else
-extern void rcu_nmi_enter(void);
-extern void rcu_nmi_exit(void);
-#endif
-
 /*
  * NMI vs Tracing
  * --------------
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 923e4fa04338..79ea1a45adf0 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -105,14 +105,6 @@ static inline void rcu_sysrq_start(void) { }
 static inline void rcu_sysrq_end(void) { }
 #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
 
-#ifdef CONFIG_NO_HZ_FULL
-void rcu_user_enter(void);
-void rcu_user_exit(void);
-#else
-static inline void rcu_user_enter(void) { }
-static inline void rcu_user_exit(void) { }
-#endif /* CONFIG_NO_HZ_FULL */
-
 #ifdef CONFIG_RCU_NOCB_CPU
 void rcu_init_nohz(void);
 int rcu_nocb_cpu_offload(int cpu);
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 5921d9ae7ab5..430aac8a7344 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -86,8 +86,6 @@ static inline int rcu_needs_cpu(void)
 static inline void rcu_virt_note_context_switch(int cpu) { }
 static inline void rcu_cpu_stall_reset(void) { }
 static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
-static inline void rcu_idle_enter(void) { }
-static inline void rcu_idle_exit(void) { }
 static inline void rcu_irq_exit_check_preempt(void) { }
 #define rcu_is_idle_cpu(cpu) \
 	(is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq())
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index d9e8e6233c47..72131447762e 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -47,8 +47,6 @@ unsigned long start_poll_synchronize_rcu(void);
 bool poll_state_synchronize_rcu(unsigned long oldstate);
 void cond_synchronize_rcu(unsigned long oldstate);
 
-void rcu_idle_enter(void);
-void rcu_idle_exit(void);
 bool rcu_is_idle_cpu(int cpu);
 
 #ifdef CONFIG_PROVE_RCU
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 279fb5875dd8..b906fb55903b 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -140,52 +140,17 @@ static noinstr void rcu_eqs_enter(bool user)
 }
 
 /**
- * rcu_idle_enter - inform RCU that current CPU is entering idle
- *
- * Enter idle mode, in other words, -leave- the mode in which RCU
- * read-side critical sections can occur.  (Though RCU read-side
- * critical sections can occur in irq handlers in idle, a possibility
- * handled by irq_enter() and irq_exit().)
- *
- * If you add or remove a call to rcu_idle_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_idle_enter(void)
-{
-	lockdep_assert_irqs_disabled();
-	rcu_eqs_enter(false);
-}
-
-#ifdef CONFIG_NO_HZ_FULL
-/**
- * rcu_user_enter - inform RCU that we are resuming userspace.
- *
- * Enter RCU idle mode right before resuming userspace.  No use of RCU
- * is permitted between this call and rcu_user_exit(). This way the
- * CPU doesn't need to maintain the tick for RCU maintenance purposes
- * when the CPU runs in userspace.
- *
- * If you add or remove a call to rcu_user_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-noinstr void rcu_user_enter(void)
-{
-	rcu_eqs_enter(true);
-}
-#endif /* CONFIG_NO_HZ_FULL */
-
-/**
- * rcu_nmi_exit - inform RCU of exit from NMI context
+ * ct_nmi_exit - inform RCU of exit from NMI context
  *
  * If we are returning from the outermost NMI handler that interrupted an
  * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
  * to let the RCU grace-period handling know that the CPU is back to
  * being RCU-idle.
  *
- * If you add or remove a call to rcu_nmi_exit(), be sure to test
+ * If you add or remove a call to ct_nmi_exit(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
  */
-noinstr void rcu_nmi_exit(void)
+noinstr void ct_nmi_exit(void)
 {
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
@@ -266,46 +231,7 @@ static void noinstr rcu_eqs_exit(bool user)
 }
 
 /**
- * rcu_idle_exit - inform RCU that current CPU is leaving idle
- *
- * Exit idle mode, in other words, -enter- the mode in which RCU
- * read-side critical sections can occur.
- *
- * If you add or remove a call to rcu_idle_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- *
- * FIXME: This function should be noinstr but the below local_irq_save() is
- * unsafe because it involves illegal RCU uses through tracing and lockdep.
- * This must be fixed first.
- */
-void rcu_idle_exit(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	rcu_eqs_exit(false);
-	local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(rcu_idle_exit);
-
-#ifdef CONFIG_NO_HZ_FULL
-/**
- * rcu_user_exit - inform RCU that we are exiting userspace.
- *
- * Exit RCU idle mode while entering the kernel because it can
- * run a RCU read side critical section anytime.
- *
- * If you add or remove a call to rcu_user_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void noinstr rcu_user_exit(void)
-{
-	rcu_eqs_exit(true);
-}
-#endif /* ifdef CONFIG_NO_HZ_FULL */
-
-/**
- * rcu_nmi_enter - inform RCU of entry to NMI context
+ * ct_nmi_enter - inform RCU of entry to NMI context
  *
  * If the CPU was idle from RCU's viewpoint, update ct->dynticks and
  * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
@@ -313,10 +239,10 @@ void noinstr rcu_user_exit(void)
  * long as the nesting level does not overflow an int.  (You will probably
  * run out of stack space first.)
  *
- * If you add or remove a call to rcu_nmi_enter(), be sure to test
+ * If you add or remove a call to ct_nmi_enter(), be sure to test
  * with CONFIG_RCU_EQS_DEBUG=y.
  */
-noinstr void rcu_nmi_enter(void)
+noinstr void ct_nmi_enter(void)
 {
 	long incby = 2;
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
@@ -431,7 +357,13 @@ void noinstr __ct_user_enter(enum ctx_state state)
 			 * that will fire and reschedule once we resume in user/guest mode.
 			 */
 			rcu_irq_work_resched();
-			rcu_user_enter();
+			/*
+			 * Enter RCU idle mode right before resuming userspace.  No use of RCU
+			 * is permitted between this call and rcu_eqs_exit(). This way the
+			 * CPU doesn't need to maintain the tick for RCU maintenance purposes
+			 * when the CPU runs in userspace.
+			 */
+			rcu_eqs_enter(true);
 		}
 		/*
 		 * Even if context tracking is disabled on this CPU, because it's outside
@@ -464,7 +396,7 @@ void ct_user_enter(enum ctx_state state)
 	/*
 	 * Some contexts may involve an exception occuring in an irq,
 	 * leading to that nesting:
-	 * ct_irq_enter() rcu_user_exit() rcu_user_exit() ct_irq_exit()
+	 * ct_irq_enter() rcu_eqs_exit(true) rcu_eqs_enter(true) ct_irq_exit()
 	 * This would mess up the dyntick_nesting count though. And rcu_irq_*()
 	 * helpers are enough to protect RCU uses inside the exception. So
 	 * just return immediately if we detect we are in an IRQ.
@@ -513,10 +445,10 @@ void noinstr __ct_user_exit(enum ctx_state state)
 	if (__this_cpu_read(context_tracking.state) == state) {
 		if (__this_cpu_read(context_tracking.active)) {
 			/*
-			 * We are going to run code that may use RCU. Inform
-			 * RCU core about that (ie: we may need the tick again).
+			 * Exit RCU idle mode while entering the kernel because it can
+			 * run a RCU read side critical section anytime.
 			 */
-			rcu_user_exit();
+			rcu_eqs_exit(true);
 			if (state == CONTEXT_USER) {
 				instrumentation_begin();
 				vtime_user_exit(current);
@@ -606,16 +538,45 @@ DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
 };
 EXPORT_SYMBOL_GPL(context_tracking);
 
-
+/**
+ * ct_idle_enter - inform RCU that current CPU is entering idle
+ *
+ * Enter idle mode, in other words, -leave- the mode in which RCU
+ * read-side critical sections can occur.  (Though RCU read-side
+ * critical sections can occur in irq handlers in idle, a possibility
+ * handled by irq_enter() and irq_exit().)
+ *
+ * If you add or remove a call to ct_idle_enter(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
 noinstr void ct_idle_enter(void)
 {
-	rcu_idle_enter();
+	lockdep_assert_irqs_disabled();
+	rcu_eqs_enter(false);
 }
 EXPORT_SYMBOL_GPL(ct_idle_enter);
 
+/**
+ * ct_idle_exit - inform RCU that current CPU is leaving idle
+ *
+ * Exit idle mode, in other words, -enter- the mode in which RCU
+ * read-side critical sections can occur.
+ *
+ * If you add or remove a call to ct_idle_exit(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ *
+ * FIXME: This function should be noinstr but the below local_irq_save() is
+ * unsafe because it involves illegal RCU uses through tracing and lockdep.
+ * This must be fixed first.
+ */
 void ct_idle_exit(void)
 {
-	rcu_idle_exit();
+	unsigned long flags;
+
+	local_irq_save(flags);
+	rcu_eqs_exit(false);
+	local_irq_restore(flags);
+
 }
 EXPORT_SYMBOL_GPL(ct_idle_exit);
 
@@ -709,13 +670,3 @@ void ct_irq_exit_irqson(void)
 	ct_irq_exit();
 	local_irq_restore(flags);
 }
-
-noinstr void ct_nmi_enter(void)
-{
-	rcu_nmi_enter();
-}
-
-noinstr void ct_nmi_exit(void)
-{
-	rcu_nmi_exit();
-}
-- 
2.25.1

[PATCH 20/21] context_tracking: Convert state to atomic_t

[Frederic Weisbecker]

Context tracking's state and dynticks counter are going to be merged
in a single field so that both updates can happen atomically and at the
same time. Prepare for that with converting the state into an atomic_t.

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>
---
 include/linux/context_tracking.h       | 18 ++----------
 include/linux/context_tracking_state.h | 40 ++++++++++++++++++++++----
 kernel/context_tracking.c              | 15 ++++++----
 3 files changed, 46 insertions(+), 27 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index cad8aecb7321..082bf47bbd18 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -56,7 +56,7 @@ static inline enum ctx_state exception_enter(void)
 	    !context_tracking_enabled())
 		return 0;
 
-	prev_ctx = this_cpu_read(context_tracking.state);
+	prev_ctx = __ct_state();
 	if (prev_ctx != CONTEXT_KERNEL)
 		ct_user_exit(prev_ctx);
 
@@ -86,26 +86,14 @@ static __always_inline void context_tracking_guest_exit(void)
 		__ct_user_exit(CONTEXT_GUEST);
 }
 
-/**
- * ct_state() - return the current context tracking state if known
- *
- * Returns the current cpu's context tracking state if context tracking
- * is enabled.  If context tracking is disabled, returns
- * CONTEXT_DISABLED.  This should be used primarily for debugging.
- */
-static __always_inline enum ctx_state ct_state(void)
-{
-	return context_tracking_enabled() ?
-		this_cpu_read(context_tracking.state) : CONTEXT_DISABLED;
-}
 #else
 static inline void user_enter(void) { }
 static inline void user_exit(void) { }
 static inline void user_enter_irqoff(void) { }
 static inline void user_exit_irqoff(void) { }
-static inline enum ctx_state exception_enter(void) { return 0; }
+static inline int exception_enter(void) { return 0; }
 static inline void exception_exit(enum ctx_state prev_ctx) { }
-static inline enum ctx_state ct_state(void) { return CONTEXT_DISABLED; }
+static inline int ct_state(void) { return -1; }
 static __always_inline bool context_tracking_guest_enter(void) { return false; }
 static inline void context_tracking_guest_exit(void) { }
 
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index ded257130987..edd9f8f5b753 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -9,6 +9,13 @@
 /* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
 #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
 
+enum ctx_state {
+	CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
+	CONTEXT_KERNEL = 0,
+	CONTEXT_USER,
+	CONTEXT_GUEST,
+};
+
 struct context_tracking {
 #ifdef CONFIG_CONTEXT_TRACKING_USER
 	/*
@@ -19,12 +26,7 @@ struct context_tracking {
 	 */
 	bool active;
 	int recursion;
-	enum ctx_state {
-		CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
-		CONTEXT_KERNEL = 0,
-		CONTEXT_USER,
-		CONTEXT_GUEST,
-	} state;
+	atomic_t state;
 #endif
 	atomic_t dynticks;		/* Even value for idle, else odd. */
 	long dynticks_nesting;		/* Track process nesting level. */
@@ -34,6 +36,11 @@ struct context_tracking {
 #ifdef CONFIG_CONTEXT_TRACKING
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
+static __always_inline int __ct_state(void)
+{
+	return atomic_read(this_cpu_ptr(&context_tracking.state));
+}
+
 static __always_inline int ct_dynticks(void)
 {
 	return atomic_read(this_cpu_ptr(&context_tracking.dynticks));
@@ -92,6 +99,27 @@ static inline bool context_tracking_enabled_this_cpu(void)
 	return context_tracking_enabled() && __this_cpu_read(context_tracking.active);
 }
 
+/**
+ * ct_state() - return the current context tracking state if known
+ *
+ * Returns the current cpu's context tracking state if context tracking
+ * is enabled.  If context tracking is disabled, returns
+ * CONTEXT_DISABLED.  This should be used primarily for debugging.
+ */
+static __always_inline int ct_state(void)
+{
+	int ret;
+
+	if (!context_tracking_enabled())
+		return CONTEXT_DISABLED;
+
+	preempt_disable();
+	ret = __ct_state();
+	preempt_enable();
+
+	return ret;
+}
+
 #else
 static inline bool context_tracking_enabled(void) { return false; }
 static inline bool context_tracking_enabled_cpu(int cpu) { return false; }
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index b906fb55903b..acbe96779e8c 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -328,6 +328,7 @@ static __always_inline void context_tracking_recursion_exit(void)
  */
 void noinstr __ct_user_enter(enum ctx_state state)
 {
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 	lockdep_assert_irqs_disabled();
 
 	/* Kernel threads aren't supposed to go to userspace */
@@ -336,8 +337,8 @@ void noinstr __ct_user_enter(enum ctx_state state)
 	if (!context_tracking_recursion_enter())
 		return;
 
-	if ( __this_cpu_read(context_tracking.state) != state) {
-		if (__this_cpu_read(context_tracking.active)) {
+	if (__ct_state() != state) {
+		if (ct->active) {
 			/*
 			 * At this stage, only low level arch entry code remains and
 			 * then we'll run in userspace. We can assume there won't be
@@ -378,7 +379,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
 		 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
 		 * is false because we know that CPU is not tickless.
 		 */
-		__this_cpu_write(context_tracking.state, state);
+		atomic_set(&ct->state, state);
 	}
 	context_tracking_recursion_exit();
 }
@@ -439,11 +440,13 @@ NOKPROBE_SYMBOL(user_enter_callable);
  */
 void noinstr __ct_user_exit(enum ctx_state state)
 {
+	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
+
 	if (!context_tracking_recursion_enter())
 		return;
 
-	if (__this_cpu_read(context_tracking.state) == state) {
-		if (__this_cpu_read(context_tracking.active)) {
+	if (__ct_state() == state) {
+		if (ct->active) {
 			/*
 			 * Exit RCU idle mode while entering the kernel because it can
 			 * run a RCU read side critical section anytime.
@@ -456,7 +459,7 @@ void noinstr __ct_user_exit(enum ctx_state state)
 				instrumentation_end();
 			}
 		}
-		__this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
+		atomic_set(&ct->state, CONTEXT_KERNEL);
 	}
 	context_tracking_recursion_exit();
 }
-- 
2.25.1

[PATCH 21/21] rcu/context_tracking: Merge dynticks counter and context tracking states

[Frederic Weisbecker]

Updating the context tracking state and the RCU dynticks counter
atomically in a single operation is a first step towards improving CPU
isolation. This makes the context tracking state updates fully ordered
and therefore allow for later enhancements such as postponing some work
while a task is running isolated in userspace until it ever comes back
to the kernel.

The state field becomes divided in two parts:

1) Two Lower bits for context tracking state:

	CONTEXT_KERNEL = 0
   	CONTEXT_IDLE = 1,
	CONTEXT_USER = 2,
	CONTEXT_GUEST = 3,

2) Higher bits for RCU eqs dynticks counting:

    RCU_DYNTICKS_IDX = 4

   The dynticks counting is always incremented by this value.
   (state & RCU_DYNTICKS_IDX) means we are NOT in an extended quiescent
   state. This makes the chance for a collision more likely between two
   RCU dynticks snapshots but wrapping up 28 bits of eqs dynticks
   increments still takes some bad luck (also rdp.dynticks_snap could be
   converted from int to long?)

Some RCU eqs functions have been renamed to better reflect their broader
scope that now include context tracking state.

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>
---
 include/linux/context_tracking.h       |  8 +--
 include/linux/context_tracking_state.h | 27 +++++---
 kernel/context_tracking.c              | 88 +++++++++++++-------------
 kernel/rcu/tree.c                      | 13 ++--
 kernel/rcu/tree_stall.h                |  4 +-
 5 files changed, 74 insertions(+), 66 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 082bf47bbd18..a0c3bf8f3bb1 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -118,16 +118,16 @@ extern void ct_idle_exit(void);
  */
 static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
 {
-	return !(arch_atomic_read(this_cpu_ptr(&context_tracking.dynticks)) & 0x1);
+	return !(arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & RCU_DYNTICKS_IDX);
 }
 
 /*
- * Increment the current CPU's context_tracking structure's ->dynticks field
+ * Increment the current CPU's context_tracking structure's ->state field
  * with ordering.  Return the new value.
  */
-static __always_inline unsigned long rcu_dynticks_inc(int incby)
+static __always_inline unsigned long ct_state_inc(int incby)
 {
-	return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.dynticks));
+	return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.state));
 }
 
 #else
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index edd9f8f5b753..0841435620cf 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -10,12 +10,20 @@
 #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
 
 enum ctx_state {
-	CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
-	CONTEXT_KERNEL = 0,
-	CONTEXT_USER,
-	CONTEXT_GUEST,
+	CONTEXT_DISABLED	= -1,	/* returned by ct_state() if unknown */
+	CONTEXT_KERNEL		= 0,
+	CONTEXT_IDLE		= 1,
+	CONTEXT_USER		= 2,
+	CONTEXT_GUEST		= 3,
+	CONTEXT_MAX		= 4,
 };
 
+/* Even value for idle, else odd. */
+#define RCU_DYNTICKS_IDX CONTEXT_MAX
+
+#define CT_STATE_MASK (CONTEXT_MAX - 1)
+#define CT_DYNTICKS_MASK (~CT_STATE_MASK)
+
 struct context_tracking {
 #ifdef CONFIG_CONTEXT_TRACKING_USER
 	/*
@@ -26,9 +34,8 @@ struct context_tracking {
 	 */
 	bool active;
 	int recursion;
+#endif
 	atomic_t state;
-#endif
-	atomic_t dynticks;		/* Even value for idle, else odd. */
 	long dynticks_nesting;		/* Track process nesting level. */
 	long dynticks_nmi_nesting;	/* Track irq/NMI nesting level. */
 };
@@ -38,24 +45,24 @@ DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
 static __always_inline int __ct_state(void)
 {
-	return atomic_read(this_cpu_ptr(&context_tracking.state));
+	return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
 }
 
 static __always_inline int ct_dynticks(void)
 {
-	return atomic_read(this_cpu_ptr(&context_tracking.dynticks));
+	return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_DYNTICKS_MASK;
 }
 
 static __always_inline int ct_dynticks_cpu(int cpu)
 {
 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
-	return atomic_read(&ct->dynticks);
+	return atomic_read(&ct->state) & CT_DYNTICKS_MASK;
 }
 
 static __always_inline int ct_dynticks_cpu_acquire(int cpu)
 {
 	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
-	return atomic_read_acquire(&ct->state);
+	return atomic_read_acquire(&ct->state) & CT_DYNTICKS_MASK;
 }
 
 static __always_inline long ct_dynticks_nesting(void)
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index acbe96779e8c..98341e1f6d1c 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -65,7 +65,7 @@ static __always_inline void rcu_dynticks_task_trace_exit(void)
  * RCU is watching prior to the call to this function and is no longer
  * watching upon return.
  */
-static noinstr void rcu_dynticks_eqs_enter(void)
+static noinstr void ct_kernel_exit_state(int offset)
 {
 	int seq;
 
@@ -75,9 +75,9 @@ static noinstr void rcu_dynticks_eqs_enter(void)
 	 * next idle sojourn.
 	 */
 	rcu_dynticks_task_trace_enter();  // Before ->dynticks update!
-	seq = rcu_dynticks_inc(1);
+	seq = ct_state_inc(offset);
 	// RCU is no longer watching.  Better be in extended quiescent state!
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & 0x1));
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & RCU_DYNTICKS_IDX));
 }
 
 /*
@@ -85,7 +85,7 @@ static noinstr void rcu_dynticks_eqs_enter(void)
  * called from an extended quiescent state, that is, RCU is not watching
  * prior to the call to this function and is watching upon return.
  */
-static noinstr void rcu_dynticks_eqs_exit(void)
+static noinstr void ct_kernel_enter_state(int offset)
 {
 	int seq;
 
@@ -94,10 +94,10 @@ static noinstr void rcu_dynticks_eqs_exit(void)
 	 * and we also must force ordering with the next RCU read-side
 	 * critical section.
 	 */
-	seq = rcu_dynticks_inc(1);
+	seq = ct_state_inc(offset);
 	// RCU is now watching.  Better not be in an extended quiescent state!
 	rcu_dynticks_task_trace_exit();  // After ->dynticks update!
-	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & 0x1));
+	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & RCU_DYNTICKS_IDX));
 }
 
 /*
@@ -108,7 +108,7 @@ static noinstr void rcu_dynticks_eqs_exit(void)
  * the possibility of usermode upcalls having messed up our count
  * of interrupt nesting level during the prior busy period.
  */
-static noinstr void rcu_eqs_enter(bool user)
+static noinstr void ct_kernel_exit(bool user, int offset)
 {
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 
@@ -128,13 +128,13 @@ static noinstr void rcu_eqs_enter(bool user)
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	rcu_preempt_deferred_qs(current);
 
-	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
-	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+	// instrumentation for the noinstr ct_kernel_exit_state()
+	instrument_atomic_write(&ct->state, sizeof(ct->state));
 
 	instrumentation_end();
 	WRITE_ONCE(ct->dynticks_nesting, 0); /* Avoid irq-access tearing. */
 	// RCU is watching here ...
-	rcu_dynticks_eqs_enter();
+	ct_kernel_exit_state(offset);
 	// ... but is no longer watching here.
 	rcu_dynticks_task_enter();
 }
@@ -143,7 +143,7 @@ static noinstr void rcu_eqs_enter(bool user)
  * ct_nmi_exit - inform RCU of exit from NMI context
  *
  * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting
+ * RCU-idle period, update ct->state and ct->dynticks_nmi_nesting
  * to let the RCU grace-period handling know that the CPU is back to
  * being RCU-idle.
  *
@@ -180,12 +180,12 @@ noinstr void ct_nmi_exit(void)
 	trace_rcu_dyntick(TPS("Startirq"), ct_dynticks_nmi_nesting(), 0, ct_dynticks());
 	WRITE_ONCE(ct->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
 
-	// instrumentation for the noinstr rcu_dynticks_eqs_enter()
-	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+	// instrumentation for the noinstr ct_kernel_exit_state()
+	instrument_atomic_write(&ct->state, sizeof(ct->state));
 	instrumentation_end();
 
 	// RCU is watching here ...
-	rcu_dynticks_eqs_enter();
+	ct_kernel_exit_state(RCU_DYNTICKS_IDX);
 	// ... but is no longer watching here.
 
 	if (!in_nmi())
@@ -200,7 +200,7 @@ noinstr void ct_nmi_exit(void)
  * allow for the possibility of usermode upcalls messing up our count of
  * interrupt nesting level during the busy period that is just now starting.
  */
-static void noinstr rcu_eqs_exit(bool user)
+static void noinstr ct_kernel_enter(bool user, int offset)
 {
 	struct context_tracking *ct = this_cpu_ptr(&context_tracking);
 	long oldval;
@@ -215,12 +215,12 @@ static void noinstr rcu_eqs_exit(bool user)
 	}
 	rcu_dynticks_task_exit();
 	// RCU is not watching here ...
-	rcu_dynticks_eqs_exit();
+	ct_kernel_enter_state(offset);
 	// ... but is watching here.
 	instrumentation_begin();
 
-	// instrumentation for the noinstr rcu_dynticks_eqs_exit()
-	instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+	// instrumentation for the noinstr ct_kernel_enter_state()
+	instrument_atomic_write(&ct->state, sizeof(ct->state));
 
 	trace_rcu_dyntick(TPS("End"), ct_dynticks_nesting(), 1, ct_dynticks());
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
@@ -233,7 +233,7 @@ static void noinstr rcu_eqs_exit(bool user)
 /**
  * ct_nmi_enter - inform RCU of entry to NMI context
  *
- * If the CPU was idle from RCU's viewpoint, update ct->dynticks and
+ * If the CPU was idle from RCU's viewpoint, update ct->state and
  * ct->dynticks_nmi_nesting to let the RCU grace-period handling know
  * that the CPU is active.  This implementation permits nested NMIs, as
  * long as the nesting level does not overflow an int.  (You will probably
@@ -264,14 +264,14 @@ noinstr void ct_nmi_enter(void)
 			rcu_dynticks_task_exit();
 
 		// RCU is not watching here ...
-		rcu_dynticks_eqs_exit();
+		ct_kernel_enter_state(RCU_DYNTICKS_IDX);
 		// ... but is watching here.
 
 		instrumentation_begin();
 		// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
-		instrument_atomic_read(&ct->dynticks, sizeof(ct->dynticks));
-		// instrumentation for the noinstr rcu_dynticks_eqs_exit()
-		instrument_atomic_write(&ct->dynticks, sizeof(ct->dynticks));
+		instrument_atomic_read(&ct->state, sizeof(ct->state));
+		// instrumentation for the noinstr ct_kernel_enter_state()
+		instrument_atomic_write(&ct->state, sizeof(ct->state));
 
 		incby = 1;
 	} else if (!in_nmi()) {
@@ -364,22 +364,23 @@ void noinstr __ct_user_enter(enum ctx_state state)
 			 * CPU doesn't need to maintain the tick for RCU maintenance purposes
 			 * when the CPU runs in userspace.
 			 */
-			rcu_eqs_enter(true);
+			ct_kernel_exit(true, RCU_DYNTICKS_IDX + state);
+		} else {
+			/*
+			 * Even if context tracking is disabled on this CPU, because it's outside
+			 * the full dynticks mask for example, we still have to keep track of the
+			 * context transitions and states to prevent inconsistency on those of
+			 * other CPUs.
+			 * If a task triggers an exception in userspace, sleep on the exception
+			 * handler and then migrate to another CPU, that new CPU must know where
+			 * the exception returns by the time we call exception_exit().
+			 * This information can only be provided by the previous CPU when it called
+			 * exception_enter().
+			 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
+			 * is false because we know that CPU is not tickless.
+			 */
+			atomic_add(state, &ct->state);
 		}
-		/*
-		 * Even if context tracking is disabled on this CPU, because it's outside
-		 * the full dynticks mask for example, we still have to keep track of the
-		 * context transitions and states to prevent inconsistency on those of
-		 * other CPUs.
-		 * If a task triggers an exception in userspace, sleep on the exception
-		 * handler and then migrate to another CPU, that new CPU must know where
-		 * the exception returns by the time we call exception_exit().
-		 * This information can only be provided by the previous CPU when it called
-		 * exception_enter().
-		 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
-		 * is false because we know that CPU is not tickless.
-		 */
-		atomic_set(&ct->state, state);
 	}
 	context_tracking_recursion_exit();
 }
@@ -451,15 +452,16 @@ void noinstr __ct_user_exit(enum ctx_state state)
 			 * Exit RCU idle mode while entering the kernel because it can
 			 * run a RCU read side critical section anytime.
 			 */
-			rcu_eqs_exit(true);
+			ct_kernel_enter(true, RCU_DYNTICKS_IDX - state);
 			if (state == CONTEXT_USER) {
 				instrumentation_begin();
 				vtime_user_exit(current);
 				trace_user_exit(0);
 				instrumentation_end();
 			}
+		} else {
+			atomic_sub(state, &ct->state);
 		}
-		atomic_set(&ct->state, CONTEXT_KERNEL);
 	}
 	context_tracking_recursion_exit();
 }
@@ -537,7 +539,7 @@ void __init context_tracking_init(void)
 DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
 		.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
 		.dynticks_nesting = 1,
-		.dynticks = ATOMIC_INIT(1),
+		.state = ATOMIC_INIT(RCU_DYNTICKS_IDX),
 };
 EXPORT_SYMBOL_GPL(context_tracking);
 
@@ -555,7 +557,7 @@ EXPORT_SYMBOL_GPL(context_tracking);
 noinstr void ct_idle_enter(void)
 {
 	lockdep_assert_irqs_disabled();
-	rcu_eqs_enter(false);
+	ct_kernel_exit(false, RCU_DYNTICKS_IDX + CONTEXT_IDLE);
 }
 EXPORT_SYMBOL_GPL(ct_idle_enter);
 
@@ -577,7 +579,7 @@ void ct_idle_exit(void)
 	unsigned long flags;
 
 	local_irq_save(flags);
-	rcu_eqs_exit(false);
+	ct_kernel_enter(false, RCU_DYNTICKS_IDX - CONTEXT_IDLE);
 	local_irq_restore(flags);
 
 }
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 16d601512da7..e04205c1c62d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -272,9 +272,9 @@ void rcu_softirq_qs(void)
  */
 static void rcu_dynticks_eqs_online(void)
 {
-	if (ct_dynticks() & 0x1)
+	if (ct_dynticks() & RCU_DYNTICKS_IDX)
 		return;
-	rcu_dynticks_inc(1);
+	ct_state_inc(RCU_DYNTICKS_IDX);
 }
 
 /*
@@ -293,7 +293,7 @@ static int rcu_dynticks_snap(int cpu)
  */
 static bool rcu_dynticks_in_eqs(int snap)
 {
-	return !(snap & 0x1);
+	return !(snap & RCU_DYNTICKS_IDX);
 }
 
 /* Return true if the specified CPU is currently idle from an RCU viewpoint.  */
@@ -321,8 +321,7 @@ bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
 	int snap;
 
 	// If not quiescent, force back to earlier extended quiescent state.
-	snap = ct_dynticks_cpu(cpu) & ~0x1;
-
+	snap = ct_dynticks_cpu(cpu) & ~RCU_DYNTICKS_IDX;
 	smp_rmb(); // Order ->dynticks and *vp reads.
 	if (READ_ONCE(*vp))
 		return false;  // Non-zero, so report failure;
@@ -348,9 +347,9 @@ notrace void rcu_momentary_dyntick_idle(void)
 	int seq;
 
 	raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
-	seq = rcu_dynticks_inc(2);
+	seq = ct_state_inc(2 * RCU_DYNTICKS_IDX);
 	/* It is illegal to call this from idle state. */
-	WARN_ON_ONCE(!(seq & 0x1));
+	WARN_ON_ONCE(!(seq & RCU_DYNTICKS_IDX));
 	rcu_preempt_deferred_qs(current);
 }
 EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 933445d826f1..f33044fd8dfc 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -467,7 +467,7 @@ static void print_cpu_stall_info(int cpu)
 	rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j);
 	if (rcuc_starved)
 		sprintf(buf, " rcuc=%ld jiffies(starved)", j);
-	pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%#lx softirq=%u/%u fqs=%ld%s%s\n",
+	pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%04x/%ld/%#lx softirq=%u/%u fqs=%ld%s%s\n",
 	       cpu,
 	       "O."[!!cpu_online(cpu)],
 	       "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],
@@ -476,7 +476,7 @@ static void print_cpu_stall_info(int cpu)
 			rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :
 				"!."[!delta],
 	       ticks_value, ticks_title,
-	       rcu_dynticks_snap(cpu) & 0xfff,
+	       rcu_dynticks_snap(cpu) & 0xffff,
 	       ct_dynticks_nesting_cpu(cpu), ct_dynticks_nmi_nesting_cpu(cpu),
 	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
 	       data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
-- 
2.25.1

Re: [PATCH 10/21] context_tracking: Take idle eqs entrypoints over RCU

[Mark Rutland]

Hi Frederic,

On Tue, May 03, 2022 at 12:00:40PM +0200, Frederic Weisbecker wrote:
> 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.

I was a bit confused looking at this, because that redirection only exists for
CONFIG_CONTEXT_TRACKING, and is empty otherwise.

I see this patch makes TREE_RCU select CONTEXT_TRACKING, which means that
works. Since that also means building the rest of the context tracking code, I
think it'd be worth mentioning that in the commit message.

Do all architectures which can use TREE_RCU today already support context
tracking? If not, do those work by default?

Thanks,
Mark.

> 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         | 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
> 

Re: [PATCH 10/21] context_tracking: Take idle eqs entrypoints over RCU

[Frederic Weisbecker]

On Tue, May 03, 2022 at 12:02:51PM +0100, Mark Rutland wrote:
> Hi Frederic,
> 
> On Tue, May 03, 2022 at 12:00:40PM +0200, Frederic Weisbecker wrote:
> > 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.
> 
> I was a bit confused looking at this, because that redirection only exists for
> CONFIG_CONTEXT_TRACKING, and is empty otherwise.
> 
> I see this patch makes TREE_RCU select CONTEXT_TRACKING, which means that
> works. Since that also means building the rest of the context tracking code, I
> think it'd be worth mentioning that in the commit message.

Not exactly, it only builds a minimal version of CONTEXT_TRACKING, which maps
to roughly the vanilla RCU-idle code.

The user tracking part (which is the vanilla CONTEXT_TRACKING) now becomes
CONFIG_CONTEXT_TRACKING_USER

> Do all architectures which can use TREE_RCU today already support context
> tracking? If not, do those work by default?

No need to, the old context tracking becomes CONFIG_CONTEXT_TRACKING_USER
which is not needed by TREE_RCU.

Ok you're right, this is all very confusing :o)

Let's clarify this, I'm going to do the following on the next version:

* The current CONFIG_CONTEXT_TRACKING becomes CONFIG_CONTEXT_TRACKING_USER.
  This part needs support from the architecture.

* The RCU-idle functions that have been moved to context tracking will become
  CONFIG_CONTEXT_TRACKING_IDLE. This part doesn't need support from the
  architecture and will be set by TREE_RCU.

Would that look clearer?

Thanks.

Re: [PATCH 10/21] context_tracking: Take idle eqs entrypoints over RCU

[Mark Rutland]

On Tue, May 03, 2022 at 01:42:25PM +0200, Frederic Weisbecker wrote:
> On Tue, May 03, 2022 at 12:02:51PM +0100, Mark Rutland wrote:
> > Hi Frederic,
> > 
> > On Tue, May 03, 2022 at 12:00:40PM +0200, Frederic Weisbecker wrote:
> > > 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.
> > 
> > I was a bit confused looking at this, because that redirection only exists for
> > CONFIG_CONTEXT_TRACKING, and is empty otherwise.
> > 
> > I see this patch makes TREE_RCU select CONTEXT_TRACKING, which means that
> > works. Since that also means building the rest of the context tracking code, I
> > think it'd be worth mentioning that in the commit message.
> 
> Not exactly, it only builds a minimal version of CONTEXT_TRACKING, which maps
> to roughly the vanilla RCU-idle code.
> 
> The user tracking part (which is the vanilla CONTEXT_TRACKING) now becomes
> CONFIG_CONTEXT_TRACKING_USER

Ah, sorry. That makes sense to me now!

> > Do all architectures which can use TREE_RCU today already support context
> > tracking? If not, do those work by default?
> 
> No need to, the old context tracking becomes CONFIG_CONTEXT_TRACKING_USER
> which is not needed by TREE_RCU.
> 
> Ok you're right, this is all very confusing :o)
> 
> Let's clarify this, I'm going to do the following on the next version:
> 
> * The current CONFIG_CONTEXT_TRACKING becomes CONFIG_CONTEXT_TRACKING_USER.
>   This part needs support from the architecture.
> 
> * The RCU-idle functions that have been moved to context tracking will become
>   CONFIG_CONTEXT_TRACKING_IDLE. This part doesn't need support from the
>   architecture and will be set by TREE_RCU.
> 
> Would that look clearer?

I think so, yes!

It would also help if the prior commit message could be explicit about
the end result: After the Kconfig rework both
CONFIG_CONTEXT_TRACKING_USER and CONFIG_CONTEXT_TRACKING exist, but
CONFIG_CONTEXT_TRACKING will only used to decide whether to build object
files with common context tracking logic.

Thanks,
Mark.

Re: [PATCH 20/21] context_tracking: Convert state to atomic_t

[nicolas saenz julienne]

On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:

[...]

> +/**
> + * ct_state() - return the current context tracking state if known
> + *
> + * Returns the current cpu's context tracking state if context tracking
> + * is enabled.  If context tracking is disabled, returns
> + * CONTEXT_DISABLED.  This should be used primarily for debugging.
> + */
> +static __always_inline int ct_state(void)
> +{
> +	int ret;
> +
> +	if (!context_tracking_enabled())
> +		return CONTEXT_DISABLED;
> +
> +	preempt_disable();
> +	ret = __ct_state();
> +	preempt_enable();
> +
> +	return ret;
> +}
> +

I can't see any use for this function with preemption enabled. You can't trust
the data due to CPU migration and it could be a source of bugs in the future.
Wouldn't it make more sense to move the burden into the callers? They all DTRT,
plus, this_cpu_ptr() will spew warnings if someone shows up and doesn't comply.

Regards,

-- 
Nicolás Sáenz

Re: [PATCH 21/21] rcu/context_tracking: Merge dynticks counter and context tracking states

[nicolas saenz julienne]

On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:

[...]

> diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
> index edd9f8f5b753..0841435620cf 100644
> --- a/include/linux/context_tracking_state.h
> +++ b/include/linux/context_tracking_state.h
> @@ -10,12 +10,20 @@
>  #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
>  
>  enum ctx_state {
> -	CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
> -	CONTEXT_KERNEL = 0,
> -	CONTEXT_USER,
> -	CONTEXT_GUEST,
> +	CONTEXT_DISABLED	= -1,	/* returned by ct_state() if unknown */
> +	CONTEXT_KERNEL		= 0,
> +	CONTEXT_IDLE		= 1,
> +	CONTEXT_USER		= 2,
> +	CONTEXT_GUEST		= 3,
> +	CONTEXT_MAX		= 4,
>  };
>  
> +/* Even value for idle, else odd. */
> +#define RCU_DYNTICKS_IDX CONTEXT_MAX
> +
> +#define CT_STATE_MASK (CONTEXT_MAX - 1)
> +#define CT_DYNTICKS_MASK (~CT_STATE_MASK)

Nit: These macros only work as long as we don't introduce new contexts. It's
maybe worth a comment.

Regards,

-- 
Nicolás Sáenz

Re: [PATCH 00/21] rcu/context-tracking: Merge RCU eqs-dynticks counter to context tracking v2

[Nicolas Saenz Julienne]

On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
> This mixes up the RCU dynticks counter and the context tracking state
> updates into a single atomic instruction. This may serve several
> purposes:
> 
> 1) Improve CPU isolation with deferring some disturbances until sensitive
>    userspace workload completes and goes to the kernel. This can take
>    several forms, for example smp_call_function_housekeeping() or
>    on_each_housekeeping_cpu() to enqueue and execute work on all
>    housekeeping CPUs. Then an atomic operation on ct->state can defer
>    the work on nohz_full CPUs until they run in kernel (or IPI them
>    if they are in kernel mode), see this proposal by Peter:
>    https://lore.kernel.org/all/20210929151723.162004989@infradead.org/#r
> 
> 2) Unearth sysidle (https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=sysidle.2017.05.11a&id=fe5ac724d81a3c7803e60c2232718f212f3f38d4)
>    This feature allowed to shutdown the tick on the last housekeeping
>    CPU once the rest of the system is fully idle. We needed some proper
>    fully ordered context tracking for that.
> 
> Inspired by Peterz: https://lore.kernel.org/all/20210929151723.162004989@infradead.org
> 
> Passed 100 hours of TREE01.
> 
> ---

For the whole series:

Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>

Thanks!

-- 
Nicolás Sáenz

Re: [PATCH 20/21] context_tracking: Convert state to atomic_t

[Frederic Weisbecker]

On Wed, May 18, 2022 at 05:09:55PM +0200, nicolas saenz julienne wrote:
> On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
> 
> [...]
> 
> > +/**
> > + * ct_state() - return the current context tracking state if known
> > + *
> > + * Returns the current cpu's context tracking state if context tracking
> > + * is enabled.  If context tracking is disabled, returns
> > + * CONTEXT_DISABLED.  This should be used primarily for debugging.
> > + */
> > +static __always_inline int ct_state(void)
> > +{
> > +	int ret;
> > +
> > +	if (!context_tracking_enabled())
> > +		return CONTEXT_DISABLED;
> > +
> > +	preempt_disable();
> > +	ret = __ct_state();
> > +	preempt_enable();
> > +
> > +	return ret;
> > +}
> > +
> 
> I can't see any use for this function with preemption enabled. You can't trust
> the data due to CPU migration and it could be a source of bugs in the future.
> Wouldn't it make more sense to move the burden into the callers? They all DTRT,
> plus, this_cpu_ptr() will spew warnings if someone shows up and doesn't comply.

I believe syscall_exit_to_user_mode_prepare() has preemption enabled.
Then it's ok if we are scheduled away right before the check, it still applies
on any CPU.

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Peter Zijlstra]

On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> Some RCU functions enter or exit into/from RCU idle mode while using
> trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> solved with using raw versions of local_irq_*() but we would then
> lose some precious debugging informations.
> 
> Another possible way to solve this may consist in using rude RCU-tasks
> in lockdep and irqsoff tracing.
> 
> In any case and until this get solved, those RCU functions can't get
> tagged as noinstr even though they should.

No need to speculate on how to solve it; the generic entry code has
alternatives that are good. It's just that reworking your architecture
isn't trivial.

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Peter Zijlstra]

On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> Some RCU functions enter or exit into/from RCU idle mode while using
> trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> solved with using raw versions of local_irq_*() but we would then
> lose some precious debugging informations.
> 
> Another possible way to solve this may consist in using rude RCU-tasks
> in lockdep and irqsoff tracing.
> 
> In any case and until this get solved, those RCU functions can't get
> tagged as noinstr even though they should.

FWIW, this also means RCU_NONIDLE() is broken. Luckily there aren't many
users left.

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Peter Zijlstra]

On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> @@ -895,6 +899,10 @@ static void noinstr rcu_eqs_exit(bool user)
>   *
>   * If you add or remove a call to rcu_idle_exit(), be sure to test with
>   * CONFIG_RCU_EQS_DEBUG=y.
> + *
> + * FIXME: This function should be noinstr but the below local_irq_save() is
> + * unsafe because it involves illegal RCU uses through tracing and lockdep.
> + * This must be fixed first.
>   */
>  void rcu_idle_exit(void)
>  {

Urgh, except this one... I'm sure I fixed that at some point. Clearly
that never made it in :/

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Frederic Weisbecker]

On Thu, May 19, 2022 at 04:48:21PM +0200, Peter Zijlstra wrote:
> On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > Some RCU functions enter or exit into/from RCU idle mode while using
> > trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> > solved with using raw versions of local_irq_*() but we would then
> > lose some precious debugging informations.
> > 
> > Another possible way to solve this may consist in using rude RCU-tasks
> > in lockdep and irqsoff tracing.
> > 
> > In any case and until this get solved, those RCU functions can't get
> > tagged as noinstr even though they should.
> 
> No need to speculate on how to solve it; the generic entry code has
> alternatives that are good. It's just that reworking your architecture
> isn't trivial.

Speaking of, please have a look at this:

https://lore.kernel.org/all/20220518162118.GA2661055@paulmck-ThinkPad-P17-Gen-1/

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Frederic Weisbecker]

On Thu, May 19, 2022 at 05:00:26PM +0200, Peter Zijlstra wrote:
> On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > @@ -895,6 +899,10 @@ static void noinstr rcu_eqs_exit(bool user)
> >   *
> >   * If you add or remove a call to rcu_idle_exit(), be sure to test with
> >   * CONFIG_RCU_EQS_DEBUG=y.
> > + *
> > + * FIXME: This function should be noinstr but the below local_irq_save() is
> > + * unsafe because it involves illegal RCU uses through tracing and lockdep.
> > + * This must be fixed first.
> >   */
> >  void rcu_idle_exit(void)
> >  {
> 
> Urgh, except this one... I'm sure I fixed that at some point. Clearly
> that never made it in :/

Most definetly the trickiest one...

Re: [PATCH 21/21] rcu/context_tracking: Merge dynticks counter and context tracking states

[Frederic Weisbecker]

On Wed, May 18, 2022 at 05:31:32PM +0200, nicolas saenz julienne wrote:
> On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
> 
> [...]
> 
> > diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
> > index edd9f8f5b753..0841435620cf 100644
> > --- a/include/linux/context_tracking_state.h
> > +++ b/include/linux/context_tracking_state.h
> > @@ -10,12 +10,20 @@
> >  #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
> >  
> >  enum ctx_state {
> > -	CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
> > -	CONTEXT_KERNEL = 0,
> > -	CONTEXT_USER,
> > -	CONTEXT_GUEST,
> > +	CONTEXT_DISABLED	= -1,	/* returned by ct_state() if unknown */
> > +	CONTEXT_KERNEL		= 0,
> > +	CONTEXT_IDLE		= 1,
> > +	CONTEXT_USER		= 2,
> > +	CONTEXT_GUEST		= 3,
> > +	CONTEXT_MAX		= 4,
> >  };
> >  
> > +/* Even value for idle, else odd. */
> > +#define RCU_DYNTICKS_IDX CONTEXT_MAX
> > +
> > +#define CT_STATE_MASK (CONTEXT_MAX - 1)
> > +#define CT_DYNTICKS_MASK (~CT_STATE_MASK)
> 
> Nit: These macros only work as long as we don't introduce new contexts. It's
> maybe worth a comment.

Ah good point, forgot that.

Thanks!

Re: [PATCH 00/21] rcu/context-tracking: Merge RCU eqs-dynticks counter to context tracking v2

[Frederic Weisbecker]

On Wed, May 18, 2022 at 05:33:02PM +0200, Nicolas Saenz Julienne wrote:
> On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
> > This mixes up the RCU dynticks counter and the context tracking state
> > updates into a single atomic instruction. This may serve several
> > purposes:
> > 
> > 1) Improve CPU isolation with deferring some disturbances until sensitive
> >    userspace workload completes and goes to the kernel. This can take
> >    several forms, for example smp_call_function_housekeeping() or
> >    on_each_housekeeping_cpu() to enqueue and execute work on all
> >    housekeeping CPUs. Then an atomic operation on ct->state can defer
> >    the work on nohz_full CPUs until they run in kernel (or IPI them
> >    if they are in kernel mode), see this proposal by Peter:
> >    https://lore.kernel.org/all/20210929151723.162004989@infradead.org/#r
> > 
> > 2) Unearth sysidle (https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=sysidle.2017.05.11a&id=fe5ac724d81a3c7803e60c2232718f212f3f38d4)
> >    This feature allowed to shutdown the tick on the last housekeeping
> >    CPU once the rest of the system is fully idle. We needed some proper
> >    fully ordered context tracking for that.
> > 
> > Inspired by Peterz: https://lore.kernel.org/all/20210929151723.162004989@infradead.org
> > 
> > Passed 100 hours of TREE01.
> > 
> > ---
> 
> For the whole series:
> 
> Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
> Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>

I hesitated to apply these but the series has changed a little, although
the fundamental bits remain.

I'll just wait for a confirmation from you on this v3.

Thanks!

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Paul E. McKenney]

On Thu, May 19, 2022 at 04:54:38PM +0200, Peter Zijlstra wrote:
> On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > Some RCU functions enter or exit into/from RCU idle mode while using
> > trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> > solved with using raw versions of local_irq_*() but we would then
> > lose some precious debugging informations.
> > 
> > Another possible way to solve this may consist in using rude RCU-tasks
> > in lockdep and irqsoff tracing.
> > 
> > In any case and until this get solved, those RCU functions can't get
> > tagged as noinstr even though they should.
> 
> FWIW, this also means RCU_NONIDLE() is broken. Luckily there aren't many
> users left.

More to the point, rcu_irq_enter_irqson() and rcu_irq_exit_irqson() need
the same help that rcu_idle_enter() and rcu_idle_exit() got earlier this
week [1], independent of RCU_NONIDLE().

Unless Frederic beats me to it, I will queue something up.

							Thanx, Paul

[1] https://lore.kernel.org/all/20220518162118.GA2661055@paulmck-ThinkPad-P17-Gen-1/

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Frederic Weisbecker]

On Thu, May 19, 2022 at 08:26:11AM -0700, Paul E. McKenney wrote:
> On Thu, May 19, 2022 at 04:54:38PM +0200, Peter Zijlstra wrote:
> > On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > > Some RCU functions enter or exit into/from RCU idle mode while using
> > > trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> > > solved with using raw versions of local_irq_*() but we would then
> > > lose some precious debugging informations.
> > > 
> > > Another possible way to solve this may consist in using rude RCU-tasks
> > > in lockdep and irqsoff tracing.
> > > 
> > > In any case and until this get solved, those RCU functions can't get
> > > tagged as noinstr even though they should.
> > 
> > FWIW, this also means RCU_NONIDLE() is broken. Luckily there aren't many
> > users left.
> 
> More to the point, rcu_irq_enter_irqson() and rcu_irq_exit_irqson() need
> the same help that rcu_idle_enter() and rcu_idle_exit() got earlier this
> week [1], independent of RCU_NONIDLE().
> 
> Unless Frederic beats me to it, I will queue something up.

It's in the patchset I just posted (02/21).

> 
> 							Thanx, Paul
> 
> [1] https://lore.kernel.org/all/20220518162118.GA2661055@paulmck-ThinkPad-P17-Gen-1/

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Paul E. McKenney]

On Thu, May 19, 2022 at 05:35:27PM +0200, Frederic Weisbecker wrote:
> On Thu, May 19, 2022 at 08:26:11AM -0700, Paul E. McKenney wrote:
> > On Thu, May 19, 2022 at 04:54:38PM +0200, Peter Zijlstra wrote:
> > > On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > > > Some RCU functions enter or exit into/from RCU idle mode while using
> > > > trace-able and lockdep-aware IRQs (un-)masking. This could be easily
> > > > solved with using raw versions of local_irq_*() but we would then
> > > > lose some precious debugging informations.
> > > > 
> > > > Another possible way to solve this may consist in using rude RCU-tasks
> > > > in lockdep and irqsoff tracing.
> > > > 
> > > > In any case and until this get solved, those RCU functions can't get
> > > > tagged as noinstr even though they should.
> > > 
> > > FWIW, this also means RCU_NONIDLE() is broken. Luckily there aren't many
> > > users left.
> > 
> > More to the point, rcu_irq_enter_irqson() and rcu_irq_exit_irqson() need
> > the same help that rcu_idle_enter() and rcu_idle_exit() got earlier this
> > week [1], independent of RCU_NONIDLE().
> > 
> > Unless Frederic beats me to it, I will queue something up.
> 
> It's in the patchset I just posted (02/21).

Even better!!!  Thank you!

							Thanx, Paul

Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

[Peter Zijlstra]

On Thu, May 19, 2022 at 05:00:26PM +0200, Peter Zijlstra wrote:
> On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > @@ -895,6 +899,10 @@ static void noinstr rcu_eqs_exit(bool user)
> >   *
> >   * If you add or remove a call to rcu_idle_exit(), be sure to test with
> >   * CONFIG_RCU_EQS_DEBUG=y.
> > + *
> > + * FIXME: This function should be noinstr but the below local_irq_save() is
> > + * unsafe because it involves illegal RCU uses through tracing and lockdep.
> > + * This must be fixed first.
> >   */
> >  void rcu_idle_exit(void)
> >  {
> 
> Urgh, except this one... I'm sure I fixed that at some point. Clearly
> that never made it in :/

I found my patches and brushed them off, see here:

  https://lkml.kernel.org/r/20220519212750.656413111@infradead.org

Re: [PATCH 20/21] context_tracking: Convert state to atomic_t

[nicolas saenz julienne]

On Thu, 2022-05-19 at 16:37 +0200, Frederic Weisbecker wrote:
> On Wed, May 18, 2022 at 05:09:55PM +0200, nicolas saenz julienne wrote:
> > On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
> > 
> > [...]
> > 
> > > +/**
> > > + * ct_state() - return the current context tracking state if known
> > > + *
> > > + * Returns the current cpu's context tracking state if context tracking
> > > + * is enabled.  If context tracking is disabled, returns
> > > + * CONTEXT_DISABLED.  This should be used primarily for debugging.
> > > + */
> > > +static __always_inline int ct_state(void)
> > > +{
> > > +	int ret;
> > > +
> > > +	if (!context_tracking_enabled())
> > > +		return CONTEXT_DISABLED;
> > > +
> > > +	preempt_disable();
> > > +	ret = __ct_state();
> > > +	preempt_enable();
> > > +
> > > +	return ret;
> > > +}
> > > +
> > 
> > I can't see any use for this function with preemption enabled. You can't trust
> > the data due to CPU migration and it could be a source of bugs in the future.
> > Wouldn't it make more sense to move the burden into the callers? They all DTRT,
> > plus, this_cpu_ptr() will spew warnings if someone shows up and doesn't comply.
> 
> I believe syscall_exit_to_user_mode_prepare() has preemption enabled.
> Then it's ok if we are scheduled away right before the check, it still applies
> on any CPU.

Fair enough.

-- 
Nicolás Sáenz