Operating Systems

process

program running with its own memory space

thread

execution unit within a process sharing memory

context switch

CPU switches from one task to another

stack memory

function calls and local variables

heap memory

dynamic memory allocation

virtual memory

per process address space mapped to physical memory

page

fixed size block of virtual memory

page fault

needed page is not in memory

mutex

lock for mutual exclusion

semaphore

counter controlling access to resource

race condition

result depends on timing of operations

deadlock

threads wait forever on each other

deadlock mutual exclusion

resource can be held by one thread

deadlock hold and wait

thread holds resource while waiting for another

deadlock no preemption

resource cannot be forcibly taken

deadlock circular wait

cycle of waiting threads

critical section

code accessing shared resource

starvation

thread waits too long for resource

scheduler

chooses which task runs

system call

program request to operating system