Conditions for deadlock to occur

• Mutual Exclusion : At least one unsharable resource - processes claim exclusive control of resources they need
• Hold and Wait : Process holds one resource while waiting for another
• No Preemption : Resources only released voluntarily - no interruption possible (i.e. cannot be forcefully withdrawn by another process)
• Circular Wait : Circular chain of processes - each waiting for a resource held by another

Deadlock is a SERIOUS problem that can occur in concurrent systems, how do you - as OS designer and developer - control deadlock ?

Four strategies - we shall look at each in term :

• Prevention
• Avoidance
• Detection
• Recovery