rcu: Use rsp->expedited_wq instead of sync_rcu_preempt_exp_wq

Now that there is an ->expedited_wq waitqueue in each rcu_state structure,
there is no need for the sync_rcu_preempt_exp_wq global variable.  This
commit therefore substitutes ->expedited_wq for sync_rcu_preempt_exp_wq.
It also initializes ->expedited_wq only once at boot instead of at the
start of each expedited grace period.

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

2 files changed, 3 insertions, 5 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 775d36cc0050..53d66ebb4811 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3556,7 +3556,6 @@ void synchronize_sched_expedited(void)
         rcu_exp_gp_seq_start(rsp);
 
         /* Stop each CPU that is online, non-idle, and not us. */
-        init_waitqueue_head(&rsp->expedited_wq);
         atomic_set(&rsp->expedited_need_qs, 1); /* Extra count avoids race. */
         for_each_online_cpu(cpu) {
                 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
@@ -4179,6 +4178,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
         }
 
         init_waitqueue_head(&rsp->gp_wq);
+        init_waitqueue_head(&rsp->expedited_wq);
         rnp = rsp->level[rcu_num_lvls - 1];
         for_each_possible_cpu(i) {
                 while (i > rnp->grphi)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index b2bf3963a0ae..72df006de798 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -535,8 +535,6 @@ void synchronize_rcu(void)
 }
 EXPORT_SYMBOL_GPL(synchronize_rcu);
 
-static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
-
 /*
  * Return non-zero if there are any tasks in RCU read-side critical
  * sections blocking the current preemptible-RCU expedited grace period.
@@ -590,7 +588,7 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
                         raw_spin_unlock_irqrestore(&rnp->lock, flags);
                         if (wake) {
                                 smp_mb(); /* EGP done before wake_up(). */
-                                wake_up(&sync_rcu_preempt_exp_wq);
+                                wake_up(&rsp->expedited_wq);
                         }
                         break;
                 }
@@ -729,7 +727,7 @@ void synchronize_rcu_expedited(void)
 
         /* Wait for snapshotted ->blkd_tasks lists to drain. */
         rnp = rcu_get_root(rsp);
-        wait_event(sync_rcu_preempt_exp_wq,
+        wait_event(rsp->expedited_wq,
                    sync_rcu_preempt_exp_done(rnp));
 
         /* Clean up and exit. */