Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Export (0) Print
Expand All

Errors in Handling Cleanup and Close Operations

Some drivers fail to distinguish the tasks required in DispatchCleanup and DispatchClose routines. The I/O manager calls a driver's DispatchCleanup routine when the last handle to a file object is closed. The DispatchClose routine is called when the last reference is released from the file object. A driver should not attempt to free resources in its DispatchCleanup routine that are attached to a file object or might be used by other DispatchXxx routines.

When calling dispatch routines, the I/O manager holds a reference to the file object for normal I/O calls. As a result, a driver can receive I/O requests for a file object after its DispatchCleanup routine has been called but before its DispatchClose routine is called. For example, a user-mode caller might close the file handle while an I/O manager request is in progress from another thread. If the driver has deleted or freed necessary resources before the I/O manager calls its DispatchClose routine, invalid pointer references and other problems could occur.



Send comments about this topic to Microsoft

© 2015 Microsoft