1. Chapter 2 Processes and Threads 2.1 Processes 2.2 Threads
2.3 Interprocess communication
2.4 Classical IPC problems
2.5 Scheduling

2. 2.1 Processes 2.1.1 The Process Model
Multiprogramming of four programs
Conceptual model of 4 independent, sequential processes
Only one program active at any instant

3. 2.1.2 Process Creation Principal events that cause process creation
System initialization
Foreground: shells interacting with users
Background: daemons like telnetd, httpd
Execution of a process creation system call
UNIX: fork and execv
Win32: CreateProcess
User request to create a new process
Initiation of a batch job

4. 2.1.3 Process Termination Conditions which terminate processes
Normal exit (voluntary)
Process completes successfully
UNIX: exit(), Win32: ExitProcess
Error exit (voluntary)
Process finds a fatal error and terminates
Fatal error (involuntary)
Process executes an illegal instruction and the kernel terminates the process
Killed by another process (involuntary)
UNIX: kill, WIn32: TerminateProcess

5. 2.1.4 Process Hierarchies
Parent creates a child process, child processes can create its own process
Forms a hierarchy
UNIX calls this a "process group"
Windows has no concept of process hierarchy
all processes are created equal

6. 2.1.5 Process States Possible process states
running: process is using the CPU
blocked: process is waiting for I/O, or event
ready: process is waiting for CPU
Transitions between states show

7. 2.1.6 Implementation of Processes (1)
Fields of a process table entry (PCB)

8. 2.1.6 Implementation of Processes (2)
Skeleton of what lowest level of OS does when an interrupt occurs

9. 2.2 Threads 2.2.1 The Thread Model (1)
(a) Three processes each with one thread
(b) One process with three threads

10. 2.2.1 The Thread Model (2) Items shared by all threads in a process
Items private to each thread

11. 2.2.1 The Thread Model (3)
All threads have the exact same address space
Share all global variables, open file, child processes, signals
Each thread has its own stack

12. A multithreaded Web server
2.2.2 Thread Usage (2)
A multithreaded Web server

13. 2.2.2 Thread Usage (3) Rough outline of code for previous slide
(a) Dispatcher thread
(b) Worker thread

14. 2.2.3 Implementing Threads in User Space
A user-level threads package

15. 2.3.4 Implementing Threads in the Kernel
A threads package managed by the kernel

16. 2.2.5 Hybrid Implementations
Multiplexing user-level threads onto kernel- level threads