Operating Systems: Concurrent and Distributed Software Design

18.4. Conditions for deadlock to exist

If all of the following conditions are true at some time in a system then deadlock exists at that time (Coffman et al., 1971).

1. A resource request can be refused

   The system's concurrency control policy is such that objects can be acquired for exclusive use or some specific shared use. It is possible for a process to be refused access to an object on the grounds that some other process has acquired it for exclusive use. It is possible for a process to be refused access to an object on the grounds that a group of processes have acquired shared access to it for a specific purpose. An example is that a process may request exclusive access to an object in order to write to it but is refused because the object is ...