Priority Inversion

Priority Inversion 
A problem in which a low priority task inadvertently does not release the process for higher priority task. An operation system can take care of this it by appropriate provisions. 

P and V semaphore

P and V semaphore 
The semaphore functions defined as mutex or counting semaphore , or to solve the classical producer- consumer problem when using a bounded buffer. 

Buffer

Buffer
A memory block for a queue or list of messages or stream of bytes between and output source and input sink, for examples, between the tasks, files, computer and printer, physical devices and network.

Counting Semaphore

Counting Semaphore
A semaphore in which the value of which can be incremented and decremented and which is not a Boolean variable. 

Mutex

Mutex
A special variable used to take note of certain actions to prevent any task or process from proceeding further and at the same time let another task exclusively proceed further. Mutex helps in mutual exclusion of one task with respect to another by a scheduler in multitasking operations. 

Semaphore

Semaphore
A special variable used to take note of certain actions to prevent another task or process from proceeding. 

Share Data Problem

Share Data Problem
If  a variable is used in two different processes and another task if interrupts without before the operation on that data is completed, the operation on that data then the scared data problem arises. 

Inter Process Communication

Inter Process Communication
An output from one task passed to another task thought the scheduler and use of signals, exceptions , semaphores, queues, mailboxes, pipes, sockets, and remote procedure calls. 

Synchronization

Synchronization
To let each section of codes, tasks and ISRs run and gain get access to the CPU one after one sequentially , following a scheduling strategy, so that there is a predictable operation at any instance. 

Thread

Thread
A minimum unit of a scheduler to scheduler the CPU and other system resources. a process may consist of multiple threads. A thread has an independent process control block like a task control block and a thread also executes codes under the control of a scheduler. 

Task State

Task State
A state of task that changes on scheduler directions. A task at an instance can be in one of the four states, idle, ready, blocked and running that are controlled by the scheduler.