What is the difference between kernel threads and user threads?

Question

What is the difference between kernel threads and user threads? Is it that kernel thread are scheduled and executed in kernel mode? What are techniques used for creating kernel

Answer 1

What is the difference between kernel threads and user threads?

Kernel threads are privileged and can access things off-limits to user mode threads. Take a look at "Ring (Computer Security)" on Wikipedia. On Windows, user mode corresponds to Ring 3, while kernel mode corresponds to Ring 0.

What are techniques used for creating kernel threads?

This is extremely dependent upon the operating system.

now in case of user level threads Is it that this TCB is created in user's address space ?

The TCB records information about a thread that the kernel uses in running that thread, right? So if it were allocated in user space, the user mode thread could modify or corrupt it, which doesn't seem like a very good idea. So, don't you suppose it's created in kernel space?

What are these models? How are these models practically used?

Wikipedia seems really clear about that.