On 09/09/16 15:20, Gregor Boirie wrote:
> Using iio_device_unregister() on a device currently in use may stall
> userspace process polling for data availability (poll syscall).
>
> If device has vanished before running the iio_buffer_fileops poll hook, the
> latter will return empty poll event mask. Process will be stalled waiting
> for events that will never come (if no timeout specified).
>
> This patch ensures iio_buffer_poll() returns POLLERR if device has just
> been unregistered in order to properly notify userspace process something
> wrong happened (such as removable device unplugged).
>
> Signed-off-by: Gregor Boirie <gregor.boirie@xxxxxxxxxx>
Looks good to me.
Lars, as you were involved in the discussions of v1 could you
take a quick look.
Thanks,
Jonathan
> ---
> drivers/iio/industrialio-buffer.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 90462fc..aad5159 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -155,6 +155,7 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
> * a wait queue
> *
> * Return: (POLLIN | POLLRDNORM) if data is available for reading
> + * POLLERR if device was unregistered in our back
> * or 0 for other cases
> */
> unsigned int iio_buffer_poll(struct file *filp,
> @@ -162,13 +163,20 @@ unsigned int iio_buffer_poll(struct file *filp,
> {
> struct iio_dev *indio_dev = filp->private_data;
> struct iio_buffer *rb = indio_dev->buffer;
> + bool rdy;
>
> if (!indio_dev->info)
> - return 0;
> + return POLLERR;
>
> poll_wait(filp, &rb->pollq, wait);
> - if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
> + rdy = iio_buffer_ready(indio_dev, rb, rb->watermark, 0);
> +
> + if (!indio_dev->info)
> + return POLLERR;
> +
> + if (rdy)
> return POLLIN | POLLRDNORM;
> +
> return 0;
> }
>
>
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