Lock/Synchronization to protect PAB

[coderarjob]

Description

Currently allocation and freeing methods are not 'thread-safe'. When more than processes/threads of execution, can calls the PMM methods, the output is not deterministic and dangerous.

• Pages can be allocated more than once (interrupting one allocation/free, another instance of allocation/free can run and allocate the same pages twice).
• Race condition.

Tasks

• Consider implementation of Mutex