rcu: Rename qs_pending to core_needs_qs

An upcoming commit needs to invert the sense of the ->passed_quiesce
rcu_data structure field, so this commit is taking this opportunity
to clarify things a bit by renaming ->qs_pending to ->core_needs_qs.

So if !rdp->core_needs_qs, then this CPU need not concern itself with
quiescent states, in particular, it need not acquire its leaf rcu_node
structure's ->lock to check.  Otherwise, it needs to report the next
quiescent state.

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

kernel/rcu/tree.c

@@ -1746,7 +1746,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
 		trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));
 		rdp->passed_quiesce = 0;
 		rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
-		rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
+		rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);
 		zero_cpu_stall_ticks(rdp);
 		WRITE_ONCE(rdp->gpwrap, false);
 	}
@@ -2357,7 +2357,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
 	if ((rnp->qsmask & mask) == 0) {
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
 	} else {
-		rdp->qs_pending = 0;
+		rdp->core_needs_qs = 0;
 
 		/*
 		 * This GP can't end until cpu checks in, so all of our
@@ -2388,7 +2388,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
 	 * Does this CPU still need to do its part for current grace period?
 	 * If no, return and let the other CPUs do their part as well.
 	 */
-	if (!rdp->qs_pending)
+	if (!rdp->core_needs_qs)
 		return;
 
 	/*
@@ -3828,10 +3828,10 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
 
 	/* Is the RCU core waiting for a quiescent state from this CPU? */
 	if (rcu_scheduler_fully_active &&
-	    rdp->qs_pending && !rdp->passed_quiesce &&
+	    rdp->core_needs_qs && !rdp->passed_quiesce &&
 	    rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) {
-		rdp->n_rp_qs_pending++;
-	} else if (rdp->qs_pending &&
+		rdp->n_rp_core_needs_qs++;
+	} else if (rdp->core_needs_qs &&
 		   (rdp->passed_quiesce ||
 		    rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) {
 		rdp->n_rp_report_qs++;
@@ -4157,7 +4157,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
 	rdp->completed = rnp->completed;
 	rdp->passed_quiesce = false;
 	rdp->rcu_qs_ctr_snap = per_cpu(rcu_qs_ctr, cpu);
-	rdp->qs_pending = false;
+	rdp->core_needs_qs = false;
 	trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
 	raw_spin_unlock_irqrestore(&rnp->lock, flags);
 }

kernel/rcu/tree.h

@@ -303,7 +303,7 @@ struct rcu_data {
 	unsigned long	rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
 					/*  for rcu_all_qs() invocations. */
 	bool		passed_quiesce;	/* User-mode/idle loop etc. */
-	bool		qs_pending;	/* Core waits for quiesc state. */
+	bool		core_needs_qs;	/* Core waits for quiesc state. */
 	bool		beenonline;	/* CPU online at least once. */
 	bool		gpwrap;		/* Possible gpnum/completed wrap. */
 	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
@@ -368,7 +368,7 @@ struct rcu_data {
 
 	/* 5) __rcu_pending() statistics. */
 	unsigned long n_rcu_pending;	/* rcu_pending() calls since boot. */
-	unsigned long n_rp_qs_pending;
+	unsigned long n_rp_core_needs_qs;
 	unsigned long n_rp_report_qs;
 	unsigned long n_rp_cb_ready;
 	unsigned long n_rp_cpu_needs_gp;

kernel/rcu/tree_plugin.h

@@ -619,7 +619,7 @@ static void rcu_preempt_check_callbacks(void)
 		return;
 	}
 	if (t->rcu_read_lock_nesting > 0 &&
-	    __this_cpu_read(rcu_data_p->qs_pending) &&
+	    __this_cpu_read(rcu_data_p->core_needs_qs) &&
 	    !__this_cpu_read(rcu_data_p->passed_quiesce))
 		t->rcu_read_unlock_special.b.need_qs = true;
 }

kernel/rcu/tree_trace.c

@@ -123,7 +123,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
 		   ulong2long(rdp->completed), ulong2long(rdp->gpnum),
 		   rdp->passed_quiesce,
 		   rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),
-		   rdp->qs_pending);
+		   rdp->core_needs_qs);
 	seq_printf(m, " dt=%d/%llx/%d df=%lu",
 		   atomic_read(&rdp->dynticks->dynticks),
 		   rdp->dynticks->dynticks_nesting,
@@ -361,7 +361,7 @@ static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
 		   cpu_is_offline(rdp->cpu) ? '!' : ' ',
 		   rdp->n_rcu_pending);
 	seq_printf(m, "qsp=%ld rpq=%ld cbr=%ld cng=%ld ",
-		   rdp->n_rp_qs_pending,
+		   rdp->n_rp_core_needs_qs,
 		   rdp->n_rp_report_qs,
 		   rdp->n_rp_cb_ready,
 		   rdp->n_rp_cpu_needs_gp);