On 12/18/2011 10:54 PM, Jonathan Cameron wrote:
> 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?
fs/timerfd.c and also see commit 22c43c81a51
("wait_event_interruptible_locked() interface")
>>
>> 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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