Platform SDK: Win32 API

Lock Requests and Virtual Devices

The system broadcasts a message to all virtual devices (VxDs) when an application makes a request for a lock. Any VxD that uses virtual block device and I/O supervisor services to carry out direct I/O on the given volume must check for this message and either accept or reject the request when the message is received.

If the VxD rejects the request, it must return the appropriate error value. In such cases, the system does not grant the lock to the requesting application. If a VxD accepts the request, it must avoid all operations that may affect the consistency of the volume for the duration of the lock.

When the application releases the lock, the system again issues a broadcast message. The VxD can resume normal operation at this point.