rcu: Rename rcu_data's ->deferred_qs to ->exp_deferred_qs

The rcu_data structure's ->deferred_qs field is used to indicate that the
current CPU is blocking an expedited grace period (perhaps a future one).
Given that it is used only for expedited grace periods, its current name
is misleading, so this commit renames it to ->exp_deferred_qs.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

kernel/rcu/tree.h

@@ -154,7 +154,7 @@ struct rcu_data {
 	bool		core_needs_qs;	/* Core waits for quiesc state. */
 	bool		beenonline;	/* CPU online at least once. */
 	bool		gpwrap;		/* Possible ->gp_seq wrap. */
-	bool		deferred_qs;	/* This CPU awaiting a deferred QS? */
+	bool		exp_deferred_qs; /* This CPU awaiting a deferred QS? */
 	struct rcu_node *mynode;	/* This CPU's leaf of hierarchy */
 	unsigned long grpmask;		/* Mask to apply to leaf qsmask. */
 	unsigned long	ticks_this_gp;	/* The number of scheduling-clock */

kernel/rcu/tree_exp.h

@@ -250,7 +250,7 @@ static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
  */
 static void rcu_report_exp_rdp(struct rcu_data *rdp)
 {
-	WRITE_ONCE(rdp->deferred_qs, false);
+	WRITE_ONCE(rdp->exp_deferred_qs, false);
 	rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true);
 }
 
@@ -616,7 +616,7 @@ static void rcu_exp_handler(void *unused)
 		    rcu_dynticks_curr_cpu_in_eqs()) {
 			rcu_report_exp_rdp(rdp);
 		} else {
-			rdp->deferred_qs = true;
+			rdp->exp_deferred_qs = true;
 			set_tsk_need_resched(t);
 			set_preempt_need_resched();
 		}
@@ -638,7 +638,7 @@ static void rcu_exp_handler(void *unused)
 	if (t->rcu_read_lock_nesting > 0) {
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->expmask & rdp->grpmask) {
-			rdp->deferred_qs = true;
+			rdp->exp_deferred_qs = true;
 			t->rcu_read_unlock_special.b.exp_hint = true;
 		}
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -661,7 +661,7 @@ static void rcu_exp_handler(void *unused)
 	 *
 	 * Otherwise, force a context switch after the CPU enables everything.
 	 */
-	rdp->deferred_qs = true;
+	rdp->exp_deferred_qs = true;
 	if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
 	    WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs())) {
 		rcu_preempt_deferred_qs(t);

kernel/rcu/tree_plugin.h

@@ -237,10 +237,10 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
 	 * no need to check for a subsequent expedited GP.  (Though we are
 	 * still in a quiescent state in any case.)
 	 */
-	if (blkd_state & RCU_EXP_BLKD && rdp->deferred_qs)
+	if (blkd_state & RCU_EXP_BLKD && rdp->exp_deferred_qs)
 		rcu_report_exp_rdp(rdp);
 	else
-		WARN_ON_ONCE(rdp->deferred_qs);
+		WARN_ON_ONCE(rdp->exp_deferred_qs);
 }
 
 /*
@@ -337,7 +337,7 @@ void rcu_note_context_switch(bool preempt)
 	 * means that we continue to block the current grace period.
 	 */
 	rcu_qs();
-	if (rdp->deferred_qs)
+	if (rdp->exp_deferred_qs)
 		rcu_report_exp_rdp(rdp);
 	trace_rcu_utilization(TPS("End context switch"));
 	barrier(); /* Avoid RCU read-side critical sections leaking up. */
@@ -451,7 +451,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 	 */
 	special = t->rcu_read_unlock_special;
 	rdp = this_cpu_ptr(&rcu_data);
-	if (!special.s && !rdp->deferred_qs) {
+	if (!special.s && !rdp->exp_deferred_qs) {
 		local_irq_restore(flags);
 		return;
 	}
@@ -459,7 +459,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 	if (special.b.need_qs) {
 		rcu_qs();
 		t->rcu_read_unlock_special.b.need_qs = false;
-		if (!t->rcu_read_unlock_special.s && !rdp->deferred_qs) {
+		if (!t->rcu_read_unlock_special.s && !rdp->exp_deferred_qs) {
 			local_irq_restore(flags);
 			return;
 		}
@@ -471,7 +471,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 	 * tasks are handled when removing the task from the
 	 * blocked-tasks list below.
 	 */
-	if (rdp->deferred_qs) {
+	if (rdp->exp_deferred_qs) {
 		rcu_report_exp_rdp(rdp);
 		if (!t->rcu_read_unlock_special.s) {
 			local_irq_restore(flags);
@@ -560,7 +560,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
  */
 static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
 {
-	return (__this_cpu_read(rcu_data.deferred_qs) ||
+	return (__this_cpu_read(rcu_data.exp_deferred_qs) ||
 		READ_ONCE(t->rcu_read_unlock_special.s)) &&
 	       t->rcu_read_lock_nesting <= 0;
 }