Use of system cache

The implementor of callback handlers should be aware that the OS, when sending the requests to the file system, can be using the cache internally. This as the following consequences for you:
  1. The callback handler procedure must avoid using any file operations in buffered mode (both explicit and implicit). All files, access to which is done from callbacks, should be opened with FILE_FLAG_NO_BUFFERING flag.
  2. No APC (asynchronous procedure calls) should be performed.
  3. User interface operations must be strongly restricted.
Failure to follow the above restrictions will cause the system-wide deadlock.