week 8 processes Flashcards
An operating system executes a variety of programs which are: 2 examples
batch system - jobs
Time-shared systems - user programs or tasks
what is a process
a program in execution; process execution must
progress in sequential fashion
should processes execute in a concurrent or a sequential fashion
sequential.
what does a process include (3 things)
program (text) and program counter (PC)
stack
data section
name the states of a process:
new: The process is being created
running: Instructions are being executed
waiting: The process is waiting for some event to occur
ready: The process is waiting to be assigned to a processor
terminated: The process has finished execution
what is the new state in a process
The process is being created
running: Instructions are being executed
what is the running state in a process
Instructions are being executed
what is the ready state in a process
The process is waiting to be assigned to a processor
what is the waiting state in a process
The process is waiting for some event to occur
what is the terminated state in a process
The process has finished execution
what is a process control block (PCB)
Information associated with each process, which is stored as
various fields within a kernel data structure
what is stored in a pcb
Process state
Program counter
CPU registers
CPU scheduling information
Memory-management information
Accounting information
I/O status information
describe the process creation
Parent process create children processes, which, in turn create
other processes, forming a tree of processes
Generally, process identified and managed via a process
identifier (pid)
Resource sharing
Parent and children share all resources
Children share subset of parent’s resources
Parent and child share no resources
Execution
Parent and children execute concurrently
Parent waits until children terminate
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what is a process identified and managed in?
Generally, process identified and managed via a process
identifier (pid)
describe resource sharing in a process creation
Parent and children share all resources
Children share subset of parent’s resources
Parent and child share no resources
describe execution in process creation
Parent and children execute concurrently
Parent waits until children terminate
describe unix process creation example
fork system call creates new process
exec system call used after a fork to replace the process’
memory space with a new program
describe process termination
Process executes last statement and asks the operating
system to delete it (exit)
Output data from child to parent (via wait)
Process’ resources are deallocated by operating system
Parent may terminate execution of children processes (abort)
Child has exceeded allocated resources
Task assigned to child is no longer required
If parent is exiting:
Some operating systems do not allow child to continue if its
parent terminates — all children terminated (i.e. cascading
termination)
describe exit in process termination
Process executes last statement and asks the operating
system to delete it (exit)
what happens during the wait stage in process termination
Output data from child to parent (via wait)
Process’ resources are deallocated by operating system
describe the abort stage in process termination
Parent may terminate execution of children processes (abort)
Child has exceeded allocated resources
Task assigned to child is no longer required
If parent is exiting:
Some operating systems do not allow child to continue if its
parent terminates — all children terminated (i.e. cascading
termination)
what happens if parents are exiting in process termination
Some operating systems do not allow child to continue if its
parent terminates — all children terminated (i.e. cascading
termination)
what is a context switch
When CPU switches to another process, the system must save
the state of the old process and load the saved state for the
new process via a context switch
Context of a process represented in the PCB
Context-switch time is overhead; the system does no useful
work while switching
Time dependent on hardware support
where is the context of a process stored
in the PCB
context switch time type (i did not know how to word this)
overhead
context switch time is overhead , what does that mean?
Context-switch time is overhead; the system does no useful
work while switching
Time dependent on hardware support
