rcu: Use funnel locking for synchronize_rcu_expedited()'s polling loop

This commit gets rid of synchronize_rcu_expedited()'s mutex_trylock()
polling loop in favor of the funnel-locking scheme that was abstracted
from synchronize_sched_expedited().

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

1 files changed, 8 insertions, 7 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 094ed8f..338ea61 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3309,9 +3309,9 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
 	return rcu_seq_done(&rsp->expedited_sequence, s);
 }
 
-/* Common code for synchronize_sched_expedited() work-done checking. */
-static bool sync_sched_exp_wd(struct rcu_state *rsp, struct rcu_node *rnp,
-			      atomic_long_t *stat, unsigned long s)
+/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
+static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
+			       atomic_long_t *stat, unsigned long s)
 {
 	if (rcu_exp_gp_seq_done(rsp, s)) {
 		if (rnp)
@@ -3319,7 +3319,6 @@ static bool sync_sched_exp_wd(struct rcu_state *rsp, struct rcu_node *rnp,
 		/* Ensure test happens before caller kfree(). */
 		smp_mb__before_atomic(); /* ^^^ */
 		atomic_long_inc(stat);
-		put_online_cpus();
 		return true;
 	}
 	return false;
@@ -3345,14 +3344,14 @@ static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
 	 */
 	rnp0 = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
 	for (; rnp0 != NULL; rnp0 = rnp0->parent) {
-		if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone1, s))
+		if (sync_exp_work_done(rsp, rnp1, &rsp->expedited_workdone1, s))
 			return NULL;
 		mutex_lock(&rnp0->exp_funnel_mutex);
 		if (rnp1)
 			mutex_unlock(&rnp1->exp_funnel_mutex);
 		rnp1 = rnp0;
 	}
-	if (sync_sched_exp_wd(rsp, rnp1, &rsp->expedited_workdone2, s))
+	if (sync_exp_work_done(rsp, rnp1, &rsp->expedited_workdone2, s))
 		return NULL;
 	return rnp1;
 }
@@ -3402,8 +3401,10 @@ void synchronize_sched_expedited(void)
 	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
 
 	rnp = exp_funnel_lock(rsp, s);
-	if (rnp == NULL)
+	if (rnp == NULL) {
+		put_online_cpus();
 		return;  /* Someone else did our work for us. */
+	}
 
 	rcu_exp_gp_seq_start(rsp);