B requests a drive, but the resource manager blocks the request 3. A requests and gets a second drive 4. Mutual exclusion condition. Each resource is assigned to a process or is available. Hold and wait condition.
Processes holding resources can request new resources.
No preemption condition. Circular wait condition. Designing algorithms that prevent deadlock involves preventing one or more of the above conditions. When considering deadlock, it is useful to draw a resource graph that shows processes and resources. Conservative policies deny resources even when they are available.