What is the state of the processor, when a process is waiting for some event to occur?

When a process is waiting for some event to take place, most likely for the needy resources to be relased by other process or processes that are currently utilizing the resources, such as an I/O device, it is at a blocked state. Upon the availability of waited resources, after the resources being relased, the process will transit to a ready state from this blocked state.

What is Deadlock?

Deadlock is a situation in which the processes waits for the other resource which is occupied by another process in a loop for example take processes P1 and P2 and resources R1 and R2 in the deadlock condition,

• P1 -R1 waits for R2
• P2 -R2 waits for R1 so 

both processes waits for the other resource to get free for their complete operation. In such cases - One can avoid deadlocks by following methods
1) Prevention
2) Detection
3) Avoidance
4) Recovery

What is embedded system?

Electrical control system which is designed to perform predefined specific function with combination of computer hardware and software.

RISC processor

Acronym for Reduced Instruction Set Computer. A microprocessor that carries out fewer instructions than traditional microprocessors so that it can work more quickly.

What is preemptive scheduler?

A scheduler that may switch between threads at any time.

Cross Compiler

A cross compiler is a compiler capable of creating executable code for another platform than the one on which the cross compiler is run. Such a tool is handy when you want to compile code for a platform that you don't have access to, or because it is inconvenient or impossible to compile on that platform (as is the case with embedded systems.)

(en.wikipedia.org/wiki/Cross_compiler)

What is mutex?

A synchronization object that provides mutual exclusion among tasks. A mutex is often used to ensure that shared variables are always seen by other tasks in a consistent state.

Another name of mutex is 'semaphore'.

What is priority inverse? How to avoid it?

A situation where a low-priority task holds a resource
which a higher-priority task is waiting for. This can
occur with tasks scheduled with SCHED_OTHER or SCHED_IDLE,
where a task with a higher scheduling priority will always
be scheduled before in preference. This leads to deadlock as
the low-priority task cannot be scheduled in order to release
the lock, and the high-priority task can't continue without the
lock on the resource. Priority inheritance is a putative solution,
where the low-priority task temporarily takes on the priority of
the other task, enabling its scheduling and release of the lock.
However this approach can itself lead to deadlock
(FIXME: is this really true?).

www.kernelnewbies.org/glossary/

Context switch

The execution is changed from one context (thread) to another.

Definition 2 for Preemption

The act of suspending the execution of one thread
and starting (or resuming) another. The suspended
thread is said to have been "preempted" by the new
thread. In QNX, whenever a lower-priority thread is
actively consuming the CPU, and a higher-priority
thread becomes READY, the lower-priority thread is
immediately preempted by the higher-priority thread.

www.qnx.com/developer/docs/momentics_nc_docs
/neutrino/sys_arch/glossary.html

Preemption

When a thread is interrupted, and the execution is handed over to another thread using a context switch.

Kernel

The kernel of an RTOS is the part that schedules which thread gets to execute at a given point in time.

Kernal is an bridge between OS and Hardware.

Kernal is the heart the of OS, usally kernal only operate both the hardwar and software.
The operating system is nothing but wrapper of the kerenal, through OS user can achive
kernal operations easily ( user friendly ).

OS is an interface between user and computer.

Task

In this text, a task is something that needs to be done. It is often implemented in a separate thread, but does not have to be.

Process

An environment in which one or several threads run.
Examples of the context is the global memory address,
which is common for threads within a process. Note that
a process in itself does not execute code, but one or more
threads within the process can. In some systems that
does not have memory protection threads are sometimes
called processes. This should be avoided since it will only
lead to confusion.

Thread

A thread is the primitive that can execute code. It contains an instruction pointer (= program counter) and sometimes has its own stack.

RTOS and Normal OS

Difference Between RTOS and normal OS
RTOS has priority based preemption but normal OS not have.

RTOS

WHAT IS RTOS?
An operating system designed specifically for use in real-time systems that respond to external eventswithin a short and predictable time frame.