[PATCH] input: remove useless synchronize_rcu() calls

[PATCH] input: remove useless synchronize_rcu() calls

[Eric Dumazet]

There is no need to call synchronize_rcu() after a list insertion,
or a NULL->ptr assignment.

However, the reverse operations do need this call.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>,
---
 drivers/input/evdev.c    |    2 --
 drivers/input/input.c    |    1 -
 drivers/input/joydev.c   |    1 -
 drivers/input/mousedev.c |    1 -
 4 files changed, 5 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 88d8e4c..c00e751 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -159,7 +159,6 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
 		return error;
 
 	rcu_assign_pointer(evdev->grab, client);
-	synchronize_rcu();
 
 	return 0;
 }
@@ -182,7 +181,6 @@ static void evdev_attach_client(struct evdev *evdev,
 	spin_lock(&evdev->client_lock);
 	list_add_tail_rcu(&client->node, &evdev->client_list);
 	spin_unlock(&evdev->client_lock);
-	synchronize_rcu();
 }
 
 static void evdev_detach_client(struct evdev *evdev,
diff --git a/drivers/input/input.c b/drivers/input/input.c
index ebbceed..75e11c7 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -451,7 +451,6 @@ int input_grab_device(struct input_handle *handle)
 	}
 
 	rcu_assign_pointer(dev->grab, handle);
-	synchronize_rcu();
 
  out:
 	mutex_unlock(&dev->mutex);
diff --git a/drivers/input/joydev.c b/drivers/input/joydev.c
index 5688b5c..c24ec2d 100644
--- a/drivers/input/joydev.c
+++ b/drivers/input/joydev.c
@@ -180,7 +180,6 @@ static void joydev_attach_client(struct joydev *joydev,
 	spin_lock(&joydev->client_lock);
 	list_add_tail_rcu(&client->node, &joydev->client_list);
 	spin_unlock(&joydev->client_lock);
-	synchronize_rcu();
 }
 
 static void joydev_detach_client(struct joydev *joydev,
diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c
index 7630273..257e033 100644
--- a/drivers/input/mousedev.c
+++ b/drivers/input/mousedev.c
@@ -508,7 +508,6 @@ static void mousedev_attach_client(struct mousedev *mousedev,
 	spin_lock(&mousedev->client_lock);
 	list_add_tail_rcu(&client->node, &mousedev->client_list);
 	spin_unlock(&mousedev->client_lock);
-	synchronize_rcu();
 }
 
 static void mousedev_detach_client(struct mousedev *mousedev,

Re: [PATCH] input: remove useless synchronize_rcu() calls

[Dmitry Torokhov]

On Wed, May 11, 2011 at 11:25:55PM +0200, Eric Dumazet wrote:
> There is no need to call synchronize_rcu() after a list insertion,
> or a NULL->ptr assignment.
> 
> However, the reverse operations do need this call.

Applied, thanks Eric.

-- 
Dmitry