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;