On 12/16/2011 05:12 PM, Lars-Peter Clausen wrote:
> Use the waitqueue lock to protect the event queue instead of a custom mutex.
> This has the advantage that we can call the waitqueue operations with the lock
> held, which simplifies the code flow a bit.
Didn't realise this was an option. I'm not finding all that many places
doing this. Could you point out some examples to compare with?
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> ---
> drivers/staging/iio/industrialio-event.c | 43 ++++++++++++-----------------
> 1 files changed, 18 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/staging/iio/industrialio-event.c b/drivers/staging/iio/industrialio-event.c
> index 50d03bd..ef4943a 100644
> --- a/drivers/staging/iio/industrialio-event.c
> +++ b/drivers/staging/iio/industrialio-event.c
> @@ -34,7 +34,6 @@
> */
> struct iio_event_interface {
> wait_queue_head_t wait;
> - struct mutex event_list_lock;
> DECLARE_KFIFO(det_events, struct iio_event_data, 16);
>
> struct list_head dev_attr_list;
> @@ -49,19 +48,17 @@ int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp)
> int ret = 0;
>
> /* Does anyone care? */
> - mutex_lock(&ev_int->event_list_lock);
> + spin_lock(&ev_int->wait.lock);
> if (test_bit(IIO_BUSY_BIT_POS, &ev_int->flags)) {
>
> ev.id = ev_code;
> ev.timestamp = timestamp;
>
> ret = kfifo_put(&ev_int->det_events, &ev);
> -
> - mutex_unlock(&ev_int->event_list_lock);
> if (ret != 0)
> - wake_up_interruptible(&ev_int->wait);
> - } else
> - mutex_unlock(&ev_int->event_list_lock);
> + wake_up_locked(&ev_int->wait);
> + }
> + spin_unlock(&ev_int->wait.lock);
>
> return ret;
> }
> @@ -79,28 +76,25 @@ static ssize_t iio_event_chrdev_read(struct file *filep,
> if (count < sizeof(struct iio_event_data))
> return -EINVAL;
>
> - mutex_lock(&ev_int->event_list_lock);
> + spin_lock(&ev_int->wait.lock);
> if (kfifo_is_empty(&ev_int->det_events)) {
> if (filep->f_flags & O_NONBLOCK) {
> ret = -EAGAIN;
> - goto error_mutex_unlock;
> + goto error_unlock;
> }
> - mutex_unlock(&ev_int->event_list_lock);
> /* Blocking on device; waiting for something to be there */
> - ret = wait_event_interruptible(ev_int->wait,
> + ret = wait_event_interruptible_locked(ev_int->wait,
> !kfifo_is_empty(&ev_int->det_events));
> if (ret)
> - goto error_ret;
> + goto error_unlock;
> /* Single access device so no one else can get the data */
> - mutex_lock(&ev_int->event_list_lock);
> }
>
> - mutex_unlock(&ev_int->event_list_lock);
> ret = kfifo_to_user(&ev_int->det_events, buf, count, &copied);
>
> -error_mutex_unlock:
> - mutex_unlock(&ev_int->event_list_lock);
> -error_ret:
> +error_unlock:
> + spin_unlock(&ev_int->wait.lock);
> +
> return ret ? ret : copied;
> }
>
> @@ -108,10 +102,10 @@ static int iio_event_chrdev_release(struct inode *inode, struct file *filep)
> {
> struct iio_event_interface *ev_int = filep->private_data;
>
> - mutex_lock(&ev_int->event_list_lock);
> + spin_lock(&ev_int->wait.lock);
> clear_bit(IIO_BUSY_BIT_POS, &ev_int->flags);
> kfifo_reset_out(&ev_int->det_events);
> - mutex_unlock(&ev_int->event_list_lock);
> + spin_unlock(&ev_int->wait.lock);
>
> return 0;
> }
> @@ -131,18 +125,18 @@ int iio_event_getfd(struct iio_dev *indio_dev)
> if (ev_int == NULL)
> return -ENODEV;
>
> - mutex_lock(&ev_int->event_list_lock);
> + spin_lock(&ev_int->wait.lock);
> if (test_and_set_bit(IIO_BUSY_BIT_POS, &ev_int->flags)) {
> - mutex_unlock(&ev_int->event_list_lock);
> + spin_unlock(&ev_int->wait.lock);
> return -EBUSY;
> }
> - mutex_unlock(&ev_int->event_list_lock);
> + spin_unlock(&ev_int->wait.lock);
> fd = anon_inode_getfd("iio:event",
> &iio_event_chrdev_fileops, ev_int, O_RDONLY);
> if (fd < 0) {
> - mutex_lock(&ev_int->event_list_lock);
> + spin_lock(&ev_int->wait.lock);
> clear_bit(IIO_BUSY_BIT_POS, &ev_int->flags);
> - mutex_unlock(&ev_int->event_list_lock);
> + spin_unlock(&ev_int->wait.lock);
> }
> return fd;
> }
> @@ -351,7 +345,6 @@ static bool iio_check_for_dynamic_events(struct iio_dev *indio_dev)
>
> static void iio_setup_ev_int(struct iio_event_interface *ev_int)
> {
> - mutex_init(&ev_int->event_list_lock);
> INIT_KFIFO(ev_int->det_events);
> init_waitqueue_head(&ev_int->wait);
> }
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