Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Wei Yang <richard.weiyang@gmail.com>
To:     paulmck@kernel.org, josh@joshtriplett.org
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
        Wei Yang <richard.weiyang@gmail.com>
Subject: [PATCH] rcu: init and destroy rcu_synchronize when necessary
Date:   Wed, 15 Apr 2020 22:26:55 +0000
Message-Id: <20200415222655.9006-1-richard.weiyang@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

We would skip the rcu_synchronize if it is a duplicate call back function.

This is not necessary to init and destroy for them.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
---
 kernel/rcu/update.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 6c4b862f57d6..91e44b527aad 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -353,13 +353,14 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
 			might_sleep();
 			continue;
 		}
-		init_rcu_head_on_stack(&rs_array[i].head);
-		init_completion(&rs_array[i].completion);
 		for (j = 0; j < i; j++)
 			if (crcu_array[j] == crcu_array[i])
 				break;
-		if (j == i)
+		if (j == i) {
+			init_rcu_head_on_stack(&rs_array[i].head);
+			init_completion(&rs_array[i].completion);
 			(crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
+		}
 	}
 
 	/* Wait for all callbacks to be invoked. */
@@ -370,9 +371,10 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
 		for (j = 0; j < i; j++)
 			if (crcu_array[j] == crcu_array[i])
 				break;
-		if (j == i)
+		if (j == i) {
 			wait_for_completion(&rs_array[i].completion);
-		destroy_rcu_head_on_stack(&rs_array[i].head);
+			destroy_rcu_head_on_stack(&rs_array[i].head);
+		}
 	}
 }
 EXPORT_SYMBOL_GPL(__wait_rcu_gp);
-- 
2.23.0