rcu: Remove rcu_state_p pointer to default rcu_state structure

The rcu_state_p pointer references the default rcu_state structure,
that is, the one that call_rcu() uses, as opposed to call_rcu_bh()
and sometimes call_rcu_sched().  But there is now only one rcu_state
structure, so that one structure is by definition the default, which
means that the rcu_state_p pointer no longer serves any useful purpose.
This commit therefore removes it.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -85,7 +85,6 @@ struct rcu_state rcu_state = {
 	.ofl_lock = __SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),
 };
 
-static struct rcu_state *const rcu_state_p = &rcu_state;
 static struct rcu_data __percpu *const rcu_data_p = &rcu_data;
 LIST_HEAD(rcu_struct_flavors);
 
@@ -491,7 +490,7 @@ static int rcu_pending(void);
  */
 unsigned long rcu_get_gp_seq(void)
 {
-	return READ_ONCE(rcu_state_p->gp_seq);
+	return READ_ONCE(rcu_state.gp_seq);
 }
 EXPORT_SYMBOL_GPL(rcu_get_gp_seq);
 
@@ -510,7 +509,7 @@ EXPORT_SYMBOL_GPL(rcu_sched_get_gp_seq);
  */
 unsigned long rcu_bh_get_gp_seq(void)
 {
-	return READ_ONCE(rcu_state_p->gp_seq);
+	return READ_ONCE(rcu_state.gp_seq);
 }
 EXPORT_SYMBOL_GPL(rcu_bh_get_gp_seq);
 
@@ -522,7 +521,7 @@ EXPORT_SYMBOL_GPL(rcu_bh_get_gp_seq);
  */
 unsigned long rcu_exp_batches_completed(void)
 {
-	return rcu_state_p->expedited_sequence;
+	return rcu_state.expedited_sequence;
 }
 EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
 
@@ -541,7 +540,7 @@ EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched);
  */
 void rcu_force_quiescent_state(void)
 {
-	force_quiescent_state(rcu_state_p);
+	force_quiescent_state(&rcu_state);
 }
 EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
 
@@ -550,7 +549,7 @@ EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
  */
 void rcu_bh_force_quiescent_state(void)
 {
-	force_quiescent_state(rcu_state_p);
+	force_quiescent_state(&rcu_state);
 }
 EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
 
@@ -611,7 +610,7 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 	case RCU_FLAVOR:
 	case RCU_BH_FLAVOR:
 	case RCU_SCHED_FLAVOR:
-		rsp = rcu_state_p;
+		rsp = &rcu_state;
 		break;
 	default:
 		break;
@@ -2292,7 +2291,6 @@ rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
 
 	raw_lockdep_assert_held_rcu_node(rnp);
 	if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT)) ||
-	    WARN_ON_ONCE(rsp != rcu_state_p) ||
 	    WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) ||
 	    rnp->qsmask != 0) {
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -2604,7 +2602,6 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp))
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
 		if (rnp->qsmask == 0) {
 			if (!IS_ENABLED(CONFIG_PREEMPT) ||
-			    rsp != rcu_state_p ||
 			    rcu_preempt_blocked_readers_cgp(rnp)) {
 				/*
 				 * No point in scanning bits because they
@@ -2973,7 +2970,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func,
  */
 void call_rcu(struct rcu_head *head, rcu_callback_t func)
 {
-	__call_rcu(head, func, rcu_state_p, -1, 0);
+	__call_rcu(head, func, &rcu_state, -1, 0);
 }
 EXPORT_SYMBOL_GPL(call_rcu);
 
@@ -3000,7 +2997,7 @@ EXPORT_SYMBOL_GPL(call_rcu_sched);
 void kfree_call_rcu(struct rcu_head *head,
 		    rcu_callback_t func)
 {
-	__call_rcu(head, func, rcu_state_p, -1, 1);
+	__call_rcu(head, func, &rcu_state, -1, 1);
 }
 EXPORT_SYMBOL_GPL(kfree_call_rcu);
 
@@ -3029,7 +3026,7 @@ unsigned long get_state_synchronize_rcu(void)
 	 * before the load from ->gp_seq.
 	 */
 	smp_mb();  /* ^^^ */
-	return rcu_seq_snap(&rcu_state_p->gp_seq);
+	return rcu_seq_snap(&rcu_state.gp_seq);
 }
 EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
 
@@ -3049,7 +3046,7 @@ EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
  */
 void cond_synchronize_rcu(unsigned long oldstate)
 {
-	if (!rcu_seq_done(&rcu_state_p->gp_seq, oldstate))
+	if (!rcu_seq_done(&rcu_state.gp_seq, oldstate))
 		synchronize_rcu();
 	else
 		smp_mb(); /* Ensure GP ends before subsequent accesses. */
@@ -3308,7 +3305,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
  */
 void rcu_barrier_bh(void)
 {
-	_rcu_barrier(rcu_state_p);
+	_rcu_barrier(&rcu_state);
 }
 EXPORT_SYMBOL_GPL(rcu_barrier_bh);
 
@@ -3322,7 +3319,7 @@ EXPORT_SYMBOL_GPL(rcu_barrier_bh);
  */
 void rcu_barrier(void)
 {
-	_rcu_barrier(rcu_state_p);
+	_rcu_barrier(&rcu_state);
 }
 EXPORT_SYMBOL_GPL(rcu_barrier);
 

kernel/rcu/tree_exp.h

@@ -756,7 +756,7 @@ static void sync_sched_exp_online_cleanup(int cpu)
  */
 void synchronize_rcu_expedited(void)
 {
-	struct rcu_state *rsp = rcu_state_p;
+	struct rcu_state *rsp = &rcu_state;
 
 	RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
 			 lock_is_held(&rcu_lock_map) ||

kernel/rcu/tree_plugin.h

@@ -381,7 +381,7 @@ void rcu_note_context_switch(bool preempt)
 	 */
 	rcu_qs();
 	if (rdp->deferred_qs)
-		rcu_report_exp_rdp(rcu_state_p, rdp);
+		rcu_report_exp_rdp(&rcu_state, rdp);
 	trace_rcu_utilization(TPS("End context switch"));
 	barrier(); /* Avoid RCU read-side critical sections leaking up. */
 }
@@ -509,7 +509,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 	 * blocked-tasks list below.
 	 */
 	if (rdp->deferred_qs) {
-		rcu_report_exp_rdp(rcu_state_p, rdp);
+		rcu_report_exp_rdp(&rcu_state, rdp);
 		if (!t->rcu_read_unlock_special.s) {
 			local_irq_restore(flags);
 			return;
@@ -566,7 +566,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 							 rnp->grplo,
 							 rnp->grphi,
 							 !!rnp->gp_tasks);
-			rcu_report_unblock_qs_rnp(rcu_state_p, rnp, flags);
+			rcu_report_unblock_qs_rnp(&rcu_state, rnp, flags);
 		} else {
 			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 		}
@@ -580,7 +580,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 		 * then we need to report up the rcu_node hierarchy.
 		 */
 		if (!empty_exp && empty_exp_now)
-			rcu_report_exp_rnp(rcu_state_p, rnp, true);
+			rcu_report_exp_rnp(&rcu_state, rnp, true);
 	} else {
 		local_irq_restore(flags);
 	}
@@ -1300,7 +1300,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 	struct sched_param sp;
 	struct task_struct *t;
 
-	if (rcu_state_p != rsp)
+	if (&rcu_state != rsp)
 		return 0;
 
 	if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0)
@@ -1431,8 +1431,8 @@ static void __init rcu_spawn_boost_kthreads(void)
 	for_each_possible_cpu(cpu)
 		per_cpu(rcu_cpu_has_work, cpu) = 0;
 	BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
-	rcu_for_each_leaf_node(rcu_state_p, rnp)
-		(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
+	rcu_for_each_leaf_node(&rcu_state, rnp)
+		(void)rcu_spawn_one_boost_kthread(&rcu_state, rnp);
 }
 
 static void rcu_prepare_kthreads(int cpu)
@@ -1442,7 +1442,7 @@ static void rcu_prepare_kthreads(int cpu)
 
 	/* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
 	if (rcu_scheduler_fully_active)
-		(void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
+		(void)rcu_spawn_one_boost_kthread(&rcu_state, rnp);
 }
 
 #else /* #ifdef CONFIG_RCU_BOOST */