rcu: Switch ->dynticks to rcu_data structure, remove rcu_dynticks

This commit move ->dynticks from the rcu_dynticks structure to the
rcu_data structure, replacing the field of the same name.  It also updates
the code to access ->dynticks from the rcu_data structure and to use the
rcu_data structure rather than following to now-gone ->dynticks field
to the now-gone rcu_dynticks structure.  While in the area, this commit
also fixes up comments.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 41 insertions, 51 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index bfa264a6f3fc..32f500fb24d3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -73,9 +73,20 @@
 
 /* Data structures. */
 
+/*
+ * Steal a bit from the bottom of ->dynticks for idle entry/exit
+ * control.  Initially this is for TLB flushing.
+ */
+#define RCU_DYNTICK_CTRL_MASK 0x1
+#define RCU_DYNTICK_CTRL_CTR  (RCU_DYNTICK_CTRL_MASK + 1)
+#ifndef rcu_eqs_special_exit
+#define rcu_eqs_special_exit() do { } while (0)
+#endif
+
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
 	.dynticks_nesting = 1,
 	.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
+	.dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
 };
 struct rcu_state rcu_state = {
 	.level = { &rcu_state.node[0] },
@@ -203,26 +214,12 @@ void rcu_softirq_qs(void)
 }
 
 /*
- * Steal a bit from the bottom of ->dynticks for idle entry/exit
- * control.  Initially this is for TLB flushing.
- */
-#define RCU_DYNTICK_CTRL_MASK 0x1
-#define RCU_DYNTICK_CTRL_CTR  (RCU_DYNTICK_CTRL_MASK + 1)
-#ifndef rcu_eqs_special_exit
-#define rcu_eqs_special_exit() do { } while (0)
-#endif
-
-static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
-	.dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
-};
-
-/*
  * Record entry into an extended quiescent state.  This is only to be
  * called when not already in an extended quiescent state.
  */
 static void rcu_dynticks_eqs_enter(void)
 {
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	int seq;
 
 	/*
@@ -230,7 +227,7 @@ static void rcu_dynticks_eqs_enter(void)
 	 * critical sections, and we also must force ordering with the
 	 * next idle sojourn.
 	 */
-	seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks);
+	seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
 	/* Better be in an extended quiescent state! */
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
 		     (seq & RCU_DYNTICK_CTRL_CTR));
@@ -245,7 +242,7 @@ static void rcu_dynticks_eqs_enter(void)
  */
 static void rcu_dynticks_eqs_exit(void)
 {
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	int seq;
 
 	/*
@@ -253,11 +250,11 @@ static void rcu_dynticks_eqs_exit(void)
 	 * and we also must force ordering with the next RCU read-side
 	 * critical section.
 	 */
-	seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks);
+	seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
 		     !(seq & RCU_DYNTICK_CTRL_CTR));
 	if (seq & RCU_DYNTICK_CTRL_MASK) {
-		atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdtp->dynticks);
+		atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
 		smp_mb__after_atomic(); /* _exit after clearing mask. */
 		/* Prefer duplicate flushes to losing a flush. */
 		rcu_eqs_special_exit();
@@ -276,11 +273,11 @@ static void rcu_dynticks_eqs_exit(void)
  */
 static void rcu_dynticks_eqs_online(void)
 {
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
-	if (atomic_read(&rdtp->dynticks) & RCU_DYNTICK_CTRL_CTR)
+	if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR)
 		return;
-	atomic_add(RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks);
+	atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
 }
 
 /*
@@ -290,18 +287,18 @@ static void rcu_dynticks_eqs_online(void)
  */
 bool rcu_dynticks_curr_cpu_in_eqs(void)
 {
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
-	return !(atomic_read(&rdtp->dynticks) & RCU_DYNTICK_CTRL_CTR);
+	return !(atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
 }
 
 /*
  * Snapshot the ->dynticks counter with full ordering so as to allow
  * stable comparison of this counter with past and future snapshots.
  */
-int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
+int rcu_dynticks_snap(struct rcu_data *rdp)
 {
-	int snap = atomic_add_return(0, &rdtp->dynticks);
+	int snap = atomic_add_return(0, &rdp->dynticks);
 
 	return snap & ~RCU_DYNTICK_CTRL_MASK;
 }
@@ -316,13 +313,13 @@ static bool rcu_dynticks_in_eqs(int snap)
 }
 
 /*
- * Return true if the CPU corresponding to the specified rcu_dynticks
+ * Return true if the CPU corresponding to the specified rcu_data
  * structure has spent some time in an extended quiescent state since
  * rcu_dynticks_snap() returned the specified snapshot.
  */
-static bool rcu_dynticks_in_eqs_since(struct rcu_dynticks *rdtp, int snap)
+static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
 {
-	return snap != rcu_dynticks_snap(rdtp);
+	return snap != rcu_dynticks_snap(rdp);
 }
 
 /*
@@ -336,14 +333,14 @@ bool rcu_eqs_special_set(int cpu)
 {
 	int old;
 	int new;
-	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
 
 	do {
-		old = atomic_read(&rdtp->dynticks);
+		old = atomic_read(&rdp->dynticks);
 		if (old & RCU_DYNTICK_CTRL_CTR)
 			return false;
 		new = old | RCU_DYNTICK_CTRL_MASK;
-	} while (atomic_cmpxchg(&rdtp->dynticks, old, new) != old);
+	} while (atomic_cmpxchg(&rdp->dynticks, old, new) != old);
 	return true;
 }
 
@@ -360,11 +357,11 @@ bool rcu_eqs_special_set(int cpu)
  */
 static void __maybe_unused rcu_momentary_dyntick_idle(void)
 {
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 	int special;
 
 	raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
-	special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR, &rdtp->dynticks);
+	special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR,
+				    &this_cpu_ptr(&rcu_data)->dynticks);
 	/* It is illegal to call this from idle state. */
 	WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR));
 	rcu_preempt_deferred_qs(current);
@@ -573,9 +570,7 @@ static struct rcu_node *rcu_get_root(void)
 static void rcu_eqs_enter(bool user)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-	struct rcu_dynticks *rdtp;
 
-	rdtp = this_cpu_ptr(&rcu_dynticks);
 	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) &&
@@ -586,7 +581,7 @@ static void rcu_eqs_enter(bool user)
 	}
 
 	lockdep_assert_irqs_disabled();
-	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, rdtp->dynticks);
+	trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, rdp->dynticks);
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
 	rdp = this_cpu_ptr(&rcu_data);
 	do_nocb_deferred_wakeup(rdp);
@@ -635,7 +630,7 @@ void rcu_user_enter(void)
 
 /*
  * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update rdtp->dynticks and rdp->dynticks_nmi_nesting
+ * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting
  * to let the RCU grace-period handling know that the CPU is back to
  * being RCU-idle.
  *
@@ -645,7 +640,6 @@ void rcu_user_enter(void)
 static __always_inline void rcu_nmi_exit_common(bool irq)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-	struct rcu_dynticks __maybe_unused *rdtp = this_cpu_ptr(&rcu_dynticks);
 
 	/*
 	 * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
@@ -660,14 +654,14 @@ static __always_inline void rcu_nmi_exit_common(bool irq)
 	 * 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, rdtp->dynticks);
+		trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks);
 		WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
 			   rdp->dynticks_nmi_nesting - 2);
 		return;
 	}
 
 	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
-	trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, rdtp->dynticks);
+	trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, rdp->dynticks);
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
 
 	if (irq)
@@ -742,11 +736,9 @@ void rcu_irq_exit_irqson(void)
 static void rcu_eqs_exit(bool user)
 {
 	struct rcu_data *rdp;
-	struct rcu_dynticks *rdtp;
 	long oldval;
 
 	lockdep_assert_irqs_disabled();
-	rdtp = this_cpu_ptr(&rcu_dynticks);
 	rdp = this_cpu_ptr(&rcu_data);
 	oldval = rdp->dynticks_nesting;
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
@@ -757,7 +749,7 @@ static void rcu_eqs_exit(bool user)
 	rcu_dynticks_task_exit();
 	rcu_dynticks_eqs_exit();
 	rcu_cleanup_after_idle();
-	trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, rdtp->dynticks);
+	trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, rdp->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);
@@ -802,7 +794,7 @@ void rcu_user_exit(void)
  * rcu_nmi_enter_common - inform RCU of entry to NMI context
  * @irq: Is this call from rcu_irq_enter?
  *
- * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and
+ * If the CPU was idle from RCU's viewpoint, update rdp->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
@@ -814,7 +806,6 @@ void rcu_user_exit(void)
 static __always_inline void rcu_nmi_enter_common(bool irq)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-	struct rcu_dynticks __maybe_unused *rdtp = this_cpu_ptr(&rcu_dynticks);
 	long incby = 2;
 
 	/* Complain about underflow. */
@@ -842,7 +833,7 @@ static __always_inline void rcu_nmi_enter_common(bool irq)
 	}
 	trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
 			  rdp->dynticks_nmi_nesting,
-			  rdp->dynticks_nmi_nesting + incby, rdtp->dynticks);
+			  rdp->dynticks_nmi_nesting + incby, rdp->dynticks);
 	WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
 		   rdp->dynticks_nmi_nesting + incby);
 	barrier();
@@ -995,7 +986,7 @@ 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->dynticks);
+	rdp->dynticks_snap = rcu_dynticks_snap(rdp);
 	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);
@@ -1046,7 +1037,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 	 * read-side critical section that started before the beginning
 	 * of the current RCU grace period.
 	 */
-	if (rcu_dynticks_in_eqs_since(rdp->dynticks, rdp->dynticks_snap)) {
+	if (rcu_dynticks_in_eqs_since(rdp, rdp->dynticks_snap)) {
 		trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
 		rdp->dynticks_fqs++;
 		rcu_gpnum_ovf(rnp, rdp);
@@ -3198,9 +3189,8 @@ rcu_boot_init_percpu_data(int cpu)
 
 	/* Set up local state, ensuring consistent view of global state. */
 	rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
-	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
 	WARN_ON_ONCE(rdp->dynticks_nesting != 1);
-	WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp->dynticks)));
+	WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)));
 	rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
 	rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
 	rdp->rcu_onl_gp_seq = rcu_state.gp_seq;