Bankers Algorithm

• Processes request 1 resource at a time
• Request granted ONLY if it results in a safe state
• If request results in an unsafe state, it is denied and user holds resources and waits until request is eventually satisfied
• In finite time, all requests will be satisfied
• Can be extended to cater for multiple resource types

+ : No deadlock and not as restrictive as deadlock prevention
- : Fixed number of resources and users
Guarantees finite time - NOT - reasonable response time
Needs advanced knowledge of maximum needs
Not suitable for multi-access systems
Unnecessary delays in avoiding unsafe states which may not lead to deadlock

  
Figure 2: Bankers algorithm (safe/unsafe states)

Therefore, from Bankers algorithm :
Allow a thread (process) to proceed if :

(total available resources) - (number allocated)
(maximum remaining that might be needed by the thread (process))