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>
---
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;
}
--
2.1.4
--
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