From: Arjan van de Ven <arjan@infradead.org>
To: linux-input@vger.kernel.org
Cc: dmitry.torokhov@gmail.com, dipankar@in.ibm.com,
linux-kernel@vger.kernel.org
Subject: Question about usage of RCU in the input layer
Date: Wed, 18 Mar 2009 21:58:12 -0700 [thread overview]
Message-ID: <20090318215812.15496a86@infradead.org> (raw)
Hi,
the input layer does a "synchronize_rcu()" after a list_add_tail_rcu(), which
is costing me 1 second of boot time.....
And based on my understanding of the RCU concept, you only need to synchronize on delete,
not on addition... so I think the synchronize is entirely redundant here...
Can I have my second of boot time back please ?
diff --git a/drivers/input/input.c b/drivers/input/input.c
index 1730d73..d69ec56 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -1544,7 +1544,6 @@ int input_register_handle(struct input_handle *handle)
return error;
list_add_tail_rcu(&handle->d_node, &dev->h_list);
mutex_unlock(&dev->mutex);
- synchronize_rcu();
/*
* Since we are supposed to be called from ->connect()
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
next reply other threads:[~2009-03-19 4:57 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-19 4:58 Arjan van de Ven [this message]
2009-03-19 7:23 ` Question about usage of RCU in the input layer Dmitry Torokhov
2009-03-19 14:02 ` Arjan van de Ven
2009-03-19 8:56 ` Dipankar Sarma
2009-03-19 14:18 ` Arjan van de Ven
2009-03-20 2:07 ` Paul E. McKenney
2009-03-20 3:20 ` Arjan van de Ven
2009-03-20 4:45 ` Paul E. McKenney
2009-03-20 5:28 ` Eric Dumazet
2009-03-20 6:01 ` Dipankar Sarma
2009-03-20 6:35 ` Eric Dumazet
2009-03-20 13:50 ` Arjan van de Ven
2009-03-20 14:31 ` Paul E. McKenney
2009-03-20 18:13 ` Arjan van de Ven
2009-03-21 1:27 ` Paul E. McKenney
2009-03-21 4:58 ` Arjan van de Ven
2009-03-21 18:58 ` Paul E. McKenney
2009-03-21 19:51 ` Arjan van de Ven
2009-03-21 20:26 ` Eric Dumazet
2009-03-21 21:07 ` Paul E. McKenney
2009-03-22 3:40 ` Arjan van de Ven
2009-03-22 4:38 ` Paul E. McKenney
2009-03-22 4:51 ` Arjan van de Ven
2009-03-22 5:18 ` Paul E. McKenney
2009-03-22 5:53 ` Arjan van de Ven
2009-03-22 16:53 ` Paul E. McKenney
2009-03-22 19:46 ` Arjan van de Ven
2009-03-22 20:52 ` Paul E. McKenney
2009-03-22 22:44 ` Arjan van de Ven
2009-03-22 23:03 ` Paul E. McKenney
2009-03-22 23:16 ` Arjan van de Ven
2009-03-23 1:27 ` Paul E. McKenney
2009-04-03 1:27 ` Paul E. McKenney
2009-03-21 21:13 ` Arjan van de Ven
2009-03-20 22:21 ` Paul E. McKenney
2009-03-21 5:46 ` Dmitry Torokhov
2009-03-21 9:13 ` Eric Dumazet
2009-03-21 18:58 ` Paul E. McKenney
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