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>

kernel/rcu/tree.h

@@ -34,13 +34,6 @@
 
 #include "rcu_segcblist.h"
 
-/*
- * Dynticks per-CPU state.
- */
-struct rcu_dynticks {
-	atomic_t dynticks;	    /* Even value for idle, else odd. */
-};
-
 /* Communicate arguments to a workqueue handler. */
 struct rcu_exp_work {
 	smp_call_func_t rew_func;
@@ -194,23 +187,19 @@ struct rcu_data {
 	long		blimit;		/* Upper limit on a processed batch */
 
 	/* 3) dynticks interface. */
-	struct rcu_dynticks *dynticks;	/* Shared per-CPU dynticks state. */
 	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, need heavy quiescent state. */
+	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. */
 #ifdef CONFIG_RCU_FAST_NO_HZ
 	bool all_lazy;			/* Are all CPU's CBs lazy? */
-	unsigned long nonlazy_posted;
-				    /* # times non-lazy CBs posted to CPU. */
+	unsigned long nonlazy_posted;	/* # times non-lazy CB posted to CPU. */
 	unsigned long nonlazy_posted_snap;
-				    /* idle-period nonlazy_posted snapshot. */
-	unsigned long last_accelerate;
-				    /* Last jiffy CBs were accelerated. */
-	unsigned long last_advance_all;
-				    /* Last jiffy CBs were all advanced. */
+					/* Nonlazy_posted snapshot. */
+	unsigned long last_accelerate;	/* Last jiffy CBs were accelerated. */
+	unsigned long last_advance_all;	/* Last jiffy CBs were all advanced. */
 	int tick_nohz_enabled_snap;	/* Previously seen value from sysfs. */
 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 
@@ -426,7 +415,7 @@ extern struct rcu_state rcu_bh_state;
 extern struct rcu_state rcu_preempt_state;
 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 
-int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
+int rcu_dynticks_snap(struct rcu_data *rdp);
 
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);

kernel/rcu/tree_exp.h

@@ -360,14 +360,13 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 	for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
 		unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
 		struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
-		struct rcu_dynticks *rdtp = per_cpu_ptr(&rcu_dynticks, cpu);
 		int snap;
 
 		if (raw_smp_processor_id() == cpu ||
 		    !(rnp->qsmaskinitnext & mask)) {
 			mask_ofl_test |= mask;
 		} else {
-			snap = rcu_dynticks_snap(rdtp);
+			snap = rcu_dynticks_snap(rdp);
 			if (rcu_dynticks_in_eqs(snap))
 				mask_ofl_test |= mask;
 			else
@@ -393,8 +392,7 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
 		if (!(mask_ofl_ipi & mask))
 			continue;
 retry_ipi:
-		if (rcu_dynticks_in_eqs_since(rdp->dynticks,
-					      rdp->exp_dynticks_snap)) {
+		if (rcu_dynticks_in_eqs_since(rdp, rdp->exp_dynticks_snap)) {
 			mask_ofl_test |= mask;
 			continue;
 		}

kernel/rcu/tree_plugin.h

@@ -1802,7 +1802,6 @@ static void print_cpu_stall_info(int cpu)
 	unsigned long delta;
 	char fast_no_hz[72];
 	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
-	struct rcu_dynticks *rdtp = rdp->dynticks;
 	char *ticks_title;
 	unsigned long ticks_value;
 
@@ -1830,7 +1829,7 @@ 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(rdtp) & 0xfff,
+	       rcu_dynticks_snap(rdp) & 0xfff,
 	       rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
 	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
 	       READ_ONCE(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,