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From:   Frederic Weisbecker <frederic@kernel.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Frederic Weisbecker <frederic@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Phil Auld <pauld@redhat.com>,
        Alex Belits <abelits@marvell.com>,
        Nicolas Saenz Julienne <nsaenz@kernel.org>,
        Xiongfeng Wang <wangxiongfeng2@huawei.com>,
        Neeraj Upadhyay <quic_neeraju@quicinc.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Yu Liao <liaoyu15@huawei.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        Uladzislau Rezki <uladzislau.rezki@sony.com>,
        Joel Fernandes <joel@joelfernandes.org>
Subject: [PATCH 12/19] rcu/context_tracking: Move dynticks_nmi_nesting to context tracking
Date:   Wed,  2 Mar 2022 16:48:03 +0100
Message-Id: <20220302154810.42308-13-frederic@kernel.org>
In-Reply-To: <20220302154810.42308-1-frederic@kernel.org>
References: <20220302154810.42308-1-frederic@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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 |  4 +++
 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, 27 insertions(+), 33 deletions(-)

diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index bcb942945265..4efb97fe6518 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
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 09a77884a4e3..155534c409fc 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -234,6 +234,7 @@ 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 eccbdbdaa02e..d3cd9e7d11fa 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 8708d1a99565..c2528e65de0c 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
@@ -442,11 +441,11 @@ static int rcu_is_cpu_rrupt_from_idle(void)
 	/* Check for counter underflows */
 	RCU_LOCKDEP_WARN(__this_cpu_read(context_tracking.dynticks_nesting) < 0,
 			 "RCU dynticks_nesting counter underflow!");
-	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
+	RCU_LOCKDEP_WARN(__this_cpu_read(context_tracking.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 = __this_cpu_read(context_tracking.dynticks_nmi_nesting);
 	if (nesting > 1)
 		return false;
 
@@ -617,11 +616,10 @@ 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) {
@@ -739,7 +737,7 @@ 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.
  *
@@ -749,7 +747,6 @@ 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();
 	/*
@@ -757,25 +754,25 @@ 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,
 				  atomic_read(&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, atomic_read(&ct->dynticks));
-	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
+	trace_rcu_dyntick(TPS("Startirq"), ct->dynticks_nmi_nesting, 0, atomic_read(&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));
@@ -799,7 +796,7 @@ void rcu_irq_exit_check_preempt(void)
 
 	RCU_LOCKDEP_WARN(__this_cpu_read(context_tracking.dynticks_nesting) <= 0,
 			 "RCU dynticks_nesting counter underflow/zero!");
-	RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
+	RCU_LOCKDEP_WARN(__this_cpu_read(context_tracking.dynticks_nmi_nesting) !=
 			 DYNTICK_IRQ_NONIDLE,
 			 "Bad RCU  dynticks_nmi_nesting counter\n");
 	RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
@@ -818,11 +815,9 @@ 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) {
@@ -842,8 +837,8 @@ static void noinstr rcu_eqs_exit(bool user)
 	trace_rcu_dyntick(TPS("End"), ct->dynticks_nesting, 1, atomic_read(&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();
 }
 
@@ -946,7 +941,7 @@ 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.)
@@ -957,11 +952,10 @@ 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
@@ -995,11 +989,11 @@ 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(&ct->dynticks));
+			  ct->dynticks_nmi_nesting,
+			  ct->dynticks_nmi_nesting + incby, atomic_read(&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 8050bab08f39..56d38568292b 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -186,7 +186,6 @@ 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 30a5e0a8ddb3..9bf5cc79d5eb 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -460,7 +460,7 @@ static void print_cpu_stall_info(int cpu)
 				"!."[!delta],
 	       ticks_value, ticks_title,
 	       rcu_dynticks_snap(cpu) & 0xfff,
-	       ct->dynticks_nesting, rdp->dynticks_nmi_nesting,
+	       ct->dynticks_nesting, ct->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,
 	       falsepositive ? " (false positive?)" : "");
-- 
2.25.1