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Deleting I/O Queues

Last Updated: 4/22/2017

Framework-based drivers must delete only some of the I/O queues that they create. If a driver creates a default I/O queue or an I/O queue that it configures by calling WdfDeviceConfigureRequestDispatching, the framework deletes the queue object for the driver.

For example, if you intend for each device's I/O queues to exist as long as each device remains plugged into the system, your driver will create its I/O queues in its EvtDriverDeviceAdd callback function. Your driver might create a default queue that receives all requests except read requests and a separate queue that receives only read requests.

The driver cannot delete these I/O queues. Instead, the framework deletes the queue objects when it deletes the device object to which the queue belongs. For information about why your driver cannot delete these I/O queues, see the following note.

If, however, your driver creates temporary I/O queues outside of its EvtDriverDeviceAdd callback function, it must call WdfObjectDelete to delete these queues when it has finished using them. For example, a driver that provides an EvtDeviceFileCreate callback function might create an I/O queue to handle I/O requests that are associated with a particular framework file object. In this case the driver's EvtFileCleanup callback function must call WdfIoQueuePurge to purge the queue and then call WdfObjectDelete to delete it.

Note The framework does not permit a driver to delete its default I/O queue, or any I/O queue that the driver configures to receive all I/O requests of a particular type (by calling WdfDeviceConfigureRequestDispatching). If your driver calls WdfObjectDelete to delete the queue object that represents one of these queues, WdfObjectDelete returns without deleting the object. WdfObjectDelete does not provide a return status, so the framework reports an error only if you are using the framework's verifier.

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