Question

Given an operating system that supports a one-to-one relationship between user-level threads and kernel-level threads and allows one or more threads from a process to issue blocking system calls while other threads (within that process) continue to run. What must a kernel provide for an effective user-level thread implementation?

Answer 1

Answer:

In this case, thread management done by the Kernel. There is no thread management code in the application area. Kernel threads are supported directly by the operating system. Any application can be programmed to be multithreaded. All of the threads within an application are supported within a single process.

The Kernel maintains context information for the process as a whole and for individuals threads within the process. Scheduling by the Kernel is done on a thread basis. The Kernel performs thread creation, scheduling and management in Kernel space. Kernel threads are generally slower to create and manage than the user threads.

ADVANTAGES

Kernel can simultaneously schedule multiple threads from the same process on multiple processes.

If one thread in a process is blocked, the Kernel can schedule another thread of the same process.

Kernel routines themselves can multithreaded.

DISADVANTAGES

Kernel threads are generally slower to create and manage than the user threads.

Transfer of control from one thread to another within same process requires a mode switch to the Kernel.