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Commit f4ecea30 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 19a5ecde

kernel/rcu/tree.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

kernel/rcu/tree_plugin.h

+2 −4
Original line number Diff line number Diff line
@@ -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. */