1 files changed, 11 insertions, 8 deletions

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 88d8e4cb419a..be0921ef6b52 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -41,6 +41,7 @@ struct evdev {
 struct evdev_client {
 	unsigned int head;
 	unsigned int tail;
+	unsigned int packet_head; /* [future] position of the first element of next packet */
 	spinlock_t buffer_lock; /* protects access to buffer, head and tail */
 	struct fasync_struct *fasync;
 	struct evdev *evdev;
@@ -72,12 +73,16 @@ static void evdev_pass_event(struct evdev_client *client,
 		client->buffer[client->tail].type = EV_SYN;
 		client->buffer[client->tail].code = SYN_DROPPED;
 		client->buffer[client->tail].value = 0;
-	}
 
-	spin_unlock(&client->buffer_lock);
+		client->packet_head = client->tail;
+	}
 
-	if (event->type == EV_SYN)
+	if (event->type == EV_SYN && event->code == SYN_REPORT) {
+		client->packet_head = client->head;
 		kill_fasync(&client->fasync, SIGIO, POLL_IN);
+	}
+
+	spin_unlock(&client->buffer_lock);
 }
 
 /*
@@ -159,7 +164,6 @@ 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 +186,6 @@ 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,
@@ -387,12 +390,12 @@ static ssize_t evdev_read(struct file *file, char __user *buffer,
 	if (count < input_event_size())
 		return -EINVAL;
 
-	if (client->head == client->tail && evdev->exist &&
+	if (client->packet_head == client->tail && evdev->exist &&
 	    (file->f_flags & O_NONBLOCK))
 		return -EAGAIN;
 
 	retval = wait_event_interruptible(evdev->wait,
-		client->head != client->tail || !evdev->exist);
+		client->packet_head != client->tail || !evdev->exist);
 	if (retval)
 		return retval;
 
@@ -421,7 +424,7 @@ static unsigned int evdev_poll(struct file *file, poll_table *wait)
 	poll_wait(file, &evdev->wait, wait);
 
 	mask = evdev->exist ? POLLOUT | POLLWRNORM : POLLHUP | POLLERR;
-	if (client->head != client->tail)
+	if (client->packet_head != client->tail)
 		mask |= POLLIN | POLLRDNORM;
 
 	return mask;