Re: [PATCH 08/10] iio: Wakeup poll and blocking reads when the device is unregistered

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On 09/21/2013 01:56 PM, Jonathan Cameron wrote:
On 09/18/13 21:02, Lars-Peter Clausen wrote:
Once the device has been unregistered there won't be any new data no matter how
long a userspace application waits, so we might as well wake them up and let
them know.

Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
This is probably the only one in the set that isn't technically a 'fix' so could you
reorder so this is at the end.  I'll then push it out once one the other patches
have made there way into the staging-next tree.


While the last two patches are fixes, there is currently no way to trigger the bug they fix since there are no users of the cb_buffer yet, so strictly speaking they don't have to go into the fixes branch.

Thanks,
---
  drivers/iio/iio_core.h            |  3 +++
  drivers/iio/industrialio-buffer.c | 16 ++++++++++++++++
  drivers/iio/industrialio-core.c   |  4 ++++
  drivers/iio/industrialio-event.c  | 21 ++++++++++++++++++++-
  4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
index 9209f47..7512cf7 100644
--- a/drivers/iio/iio_core.h
+++ b/drivers/iio/iio_core.h
@@ -50,6 +50,7 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
  #define iio_buffer_read_first_n_outer_addr (&iio_buffer_read_first_n_outer)

  void iio_disable_all_buffers(struct iio_dev *indio_dev);
+void iio_buffer_wakeup_poll(struct iio_dev *indio_dev);

  #else

@@ -57,11 +58,13 @@ void iio_disable_all_buffers(struct iio_dev *indio_dev);
  #define iio_buffer_read_first_n_outer_addr NULL

  static inline void iio_disable_all_buffers(struct iio_dev *indio_dev) {}
+static inline void iio_buffer_wakeup_poll(struct iio_dev *indio_dev) {}

  #endif

  int iio_device_register_eventset(struct iio_dev *indio_dev);
  void iio_device_unregister_eventset(struct iio_dev *indio_dev);
+void iio_device_wakeup_eventset(struct iio_dev *indio_dev);
  int iio_event_getfd(struct iio_dev *indio_dev);

  #endif
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index e9cbde3..c28625a 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -20,6 +20,7 @@
  #include <linux/cdev.h>
  #include <linux/slab.h>
  #include <linux/poll.h>
+#include <linux/sched.h>

  #include <linux/iio/iio.h>
  #include "iio_core.h"
@@ -75,6 +76,21 @@ unsigned int iio_buffer_poll(struct file *filp,
  	return 0;
  }

+/**
+ * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
+ * @indio_dev: The IIO device
+ *
+ * Wakes up the event waitqueue used for poll(). Should usually
+ * be called when the device is unregistered.
+ */
+void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
+{
+	if (!indio_dev->buffer)
+		return;
+
+	wake_up(&indio_dev->buffer->pollq);
+}
+
  void iio_buffer_init(struct iio_buffer *buffer)
  {
  	INIT_LIST_HEAD(&buffer->demux_list);
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index dd7b601..88a77d9 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1140,6 +1140,10 @@ void iio_device_unregister(struct iio_dev *indio_dev)
  	iio_disable_all_buffers(indio_dev);

  	indio_dev->info = NULL;
+
+	iio_device_wakeup_eventset(indio_dev);
+	iio_buffer_wakeup_poll(indio_dev);
+
  	mutex_unlock(&indio_dev->info_exist_lock);
  }
  EXPORT_SYMBOL(iio_device_unregister);
diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
index 3843abf..6aace88 100644
--- a/drivers/iio/industrialio-event.c
+++ b/drivers/iio/industrialio-event.c
@@ -113,9 +113,14 @@ static ssize_t iio_event_chrdev_read(struct file *filep,
  		}
  		/* Blocking on device; waiting for something to be there */
  		ret = wait_event_interruptible_locked_irq(ev_int->wait,
-					!kfifo_is_empty(&ev_int->det_events));
+					!kfifo_is_empty(&ev_int->det_events) ||
+					indio_dev->info == NULL);
  		if (ret)
  			goto error_unlock;
+		if (indio_dev->info == NULL) {
+			ret = -ENODEV;
+			goto error_unlock;
+		}
  		/* Single access device so no one else can get the data */
  	}

@@ -455,6 +460,20 @@ error_ret:
  	return ret;
  }

+/**
+ * iio_device_wakeup_eventset - Wakes up the event waitqueue
+ * @indio_dev: The IIO device
+ *
+ * Wakes up the event waitqueue used for poll() and blocking read().
+ * Should usually be called when the device is unregistered.
+ */
+void iio_device_wakeup_eventset(struct iio_dev *indio_dev)
+{
+	if (indio_dev->event_interface == NULL)
+		return;
+	wake_up(&indio_dev->event_interface->wait);
+}
+
  void iio_device_unregister_eventset(struct iio_dev *indio_dev)
  {
  	if (indio_dev->event_interface == NULL)


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