};
struct evdev_client {
- int head;
- int tail;
+ 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;
struct list_head node;
- int bufsize;
+ unsigned int bufsize;
struct input_event buffer[];
};
static void evdev_pass_event(struct evdev_client *client,
struct input_event *event)
{
- /*
- * Interrupts are disabled, just acquire the lock.
- * Make sure we don't leave with the client buffer
- * "empty" by having client->head == client->tail.
- */
+ /* Interrupts are disabled, just acquire the lock. */
spin_lock(&client->buffer_lock);
- do {
- client->buffer[client->head++] = *event;
- client->head &= client->bufsize - 1;
- } while (client->head == client->tail);
- spin_unlock(&client->buffer_lock);
- if (event->type == EV_SYN)
+ client->buffer[client->head++] = *event;
+ client->head &= client->bufsize - 1;
+
+ if (unlikely(client->head == client->tail)) {
+ /*
+ * This effectively "drops" all unconsumed events, leaving
+ * EV_SYN/SYN_DROPPED plus the newest event in the queue.
+ */
+ client->tail = (client->head - 2) & (client->bufsize - 1);
+
+ client->buffer[client->tail].time = event->time;
+ client->buffer[client->tail].type = EV_SYN;
+ client->buffer[client->tail].code = SYN_DROPPED;
+ client->buffer[client->tail].value = 0;
+
+ client->packet_head = client->tail;
+ }
+
+ 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);
}
/*
rcu_read_unlock();
- wake_up_interruptible(&evdev->wait);
+ if (type == EV_SYN && code == SYN_REPORT)
+ wake_up_interruptible(&evdev->wait);
}
static int evdev_fasync(int fd, struct file *file, int on)
return error;
rcu_assign_pointer(evdev->grab, client);
- synchronize_rcu();
return 0;
}
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,
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;
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;