Calling the mptctl_fasync() function to enable async notification caused the fasync_struct data structure, which was allocated, to never be freed. fasync_struct remained on the event list of the mptctl module even after a file was closed and released. After the file was closed, fasync_struct had an invalid file pointer which was dereferenced when the mptctl module called the kill_fasync() function to report any events. The use of the invalid file pointer could result in a deadlock on the system because the send_sigio() function tried to acquire the rwlock in the f_owner field of the previously closed file. With this update, a release callback function has been added for the file operations in the mptctl module. fasync_struct is now properly freed when a file is closed, no longer causing a deadlock.