1. Outline Process Management Process manager Hardware process
Process abstraction
Process descriptor
Thread abstraction

2. Basic OS Functions
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3. Process Manager Process manager creates the process abstraction
It implements a software environment for processes to run
Algorithms that define the behavior of the operating system
Data structures to preserve the state of the execution
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4. Process Manager – cont. Process manager consists of
Basic algorithms and data structures to implement the process and resource abstractions
Managing resources used by processes/threads
Tools to create/destroy/manipulate processes and threads
Scheduling
Process synchronization
A deadlock strategy
Protection strategy
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5. Abstract Computing Environment
Process Manager – cont.
Program
Process
Abstract Computing Environment
File
Manager
Memory
Device
Protection
Deadlock
Synchronization
Description
CPU
Other H/W
Scheduler
Resource
Devices
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6. Implementing the Process Abstraction
OS Address
Space
Control
Unit
OS interface …
Machine Executable Memory
ALU
CPU
Pi Address
Pi CPU
Pi Executable
Memory
Pk Address
Pk CPU
Pk Executable
Pj Address
Pj CPU
Pj Executable
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7. External View of the Process Manager
Hardware
Application
Program
Device Mgr
Process Mgr
Memory Mgr
File Mgr
UNIX
Windows
CreateThread()
CreateProcess()
CloseHandle()
WaitForSingleObject()
fork()
exec()
wait()
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8. Modern Processes and Threads
OS interface …
Pi CPU
Thrdj in Pi
Thrdk in Pi
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9. Modern Processes and Threads – cont.
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10. Processes A process is a sequential program in execution
The object program to be executed
The data on which the program will execute
Resources required by the program
The threads in the process
A host process environment
The status of each thread’s execution
Thread-specific data, such as a stack, a PC, and set of register values
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11. Process Address Space Process address space
A set of locations used by a process to reference primary memory locations, OS services, and resources
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12. The Address Space Process Files Other objects Address Space Binding
Executable
Memory
Other objects
Files
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13. Building the Address Space
Some parts are built into the environment
Files
System services
Some parts are imported at runtime
Mailboxes
Network connections
Memory addresses are created at compile (and run) time
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14. Process Address Space – cont.
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15. System Overview
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16. Instruction Execution
Instruction fetch (IF)
MAR  PC; IR  M[MAR]
Instruction Decode (ID)
A  Rs1; B  Rs2; PC  PC + 4
Execution (EXE)
Depends on the instruction
Memory Access (MEM)
Write-back (WB)
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17. The Hardware Process
Hardware process refers to the iterative activity of the control unit
It fetches an instruction and then executes it repeatedly
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18. Tracing the Hardware Process
Bootstrap
Loader
Process
Manager
Interrupt
Handler P1
P,2 Pn …
Machine is
Powered up
Initialization
Load the kernel
Service an interrupt
Hardware process progress
Execute a thread
Schedule
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19. Context Switching Old Thread Descriptor CPU New Thread Descriptor
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20. Context Switching – cont.
Process
Manager
Interrupt
Handler P1 P2 Pn
Executable Memory
Initialization 1 2 3 4 5 7 8 9 6
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21. The Abstract Machine Interface
User Mode
Instructions
Application Program
Abstract Machine Instructions
Trap
Instruction
Supervisor Mode
fork()
create()
open() OS
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22. Process Descriptors OS creates/manages process abstraction
Descriptor is data structure for each process
Type & location of resources it holds
List of resources it needs
List of threads
List of child processes
Security keys
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23. Process Descriptor – cont.
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24. Windows NT Process Descriptor
EPROCESS …
void *UniqueProcessId;
NT Executive
KPROCESS
uint32 KernelTime;
uint32 UserTime;
Byte state;
NT Kernel
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25. Windows NT Process Descriptor – cont.
Kernel process object including:
Pointer to the page directory
Kernel & user time
Process base priority
Process state
List of the Kernel thread descriptors that are using this process
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26. Windows NT Process Descriptor – cont.
Parent identification
Exit status
Creation and termination times.
Memory status
Security information
executable image
Process priority class used by the thread scheduler.
A list of handles used by this process
A pointer to Win32-specific information
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27. Thread Abstraction The major tasks in managing a thread include
Create/destroy a thread
Allocate thread-specific resources
Manage thread context switching
The thread descriptor is the data structure where the OS keeps all information to manage that thread
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28. Thread Abstraction – cont.
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29. Windows NT Thread Descriptor
ETHREAD
EPROCESS
KPROCESS
NT Kernel
KTHREAD
NT Executive
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30. Simple State Diagram Request Done Running Schedule Start Allocate
Ready
Blocked
Running
Start
Schedule
Request
Done
Allocate
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31. UNIX State Transition Diagram
Request
Wait by
parent
Done
Running
zombie
Schedule
Request
Sleeping
I/O Request
Start
Allocate
Runnable
I/O Complete
Resume
Traced or Stopped
Uninterruptible
Sleep
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32. Windows NT Thread States
CreateThread
Terminated
Initialized
Reinitialize
Activate
Dispatch
Exit
Wait
Waiting
Ready
Running
Wait Complete
Wait Complete
Select
Preempt
Transition
Dispatch
Standby
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33. Summary Process manager
It creates abstract machines for process to run in
It is achieved by time-multiplexing the hardware through context-switching
To manage processes / threads, process manager uses data structures (process descriptor and thread descriptor) to keep the information for manipulating them
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34. Session Information COP 4610 / CGS 5765 Section Recitation time
Section :00-08:55 AM
Section :05-09:55 AM
Section :15AM -12:05 PM
Section :20-1:10 PM
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