Chapter 13

Question 1

Does every thread has its program counter

Answer 1

Yes

Question 2

What are user level threads

Answer 2

They are created on user space by some library calls typically. Kernel do not know about these threads. A system call block the whole process

Question 3

Are solaris 2, mach C-threads, POSIX Pthreads are user level threads

Answer 3

Yes

Question 4

What are kernel level threads

Answer 4

Thread management done by kernel. Kernel aware of threads. A system call does not block the whole process.

Question 5

Does Windows NT/2000, Solaris 2 and linux are kernel level thread examples

Answer 5

Yes

Question 6

How many models are for thread implementation

Answer 6

Many-to-one model: A user level may have multiple thread but for kernel end, there will be only one thread to support it.
One-to-one model: One user thread per kernel thread
Many-to-many model: Multiple user threads multiplexed over a smaller or equal number of kernel threads

Question 7

In which thread model we have true concurrency

Answer 7

one-to-one model

Question 8

What is LWP

Answer 8

Light-weight process

Question 9

What is PThread

Answer 9

A POSIX standard API for thread creation, termination and synchronization.

Question 10

What are type of errors in threads

Answer 10

• System imposed limit to total number of threads in a process.
• Argument value is invalid
• There is not enough memory for making threads.

Question 11

What is EAGAIN error

Answer 11

System imposed limit to total number of threads in a process.

Question 12

What are 3 reasons for a thread to terminate

Answer 12

1. Main thread who create a child thread is terminated then child will also terminate
2. A thread uses return call
3. A thread uses PThread exit

Question 13

How to include PThread library in code

Answer 13

• Include POSIX library in code file

- use gcc command with -lpthread option