EXAM2

an abrupt change in control flow in response to some change in the processors state

1. Original program processes
2. Event occurs
3. An indirect procedure call is made through the jump table to an operating system subroutine (interrupt handler)
4. interrupt returns

Operating system subroutine that deals with interrupts (like a function)

an array of indexes corresponding to addresses to interrupt handlers created at system boot, AKA exception table

1. Interrupt returns to the old process and moves on
2. returns to instruction that was trying to execute before the interrupt, retries it
3. returns and moves on to a completely different program (essentially terminating the original program)

Divide by zero or segmentation fault, any hardware issue

Service calls, anything OS related

-return address is a far address so it can return with a intersegment jump
-allows jump from kernel to process
-processor saves the program status in a word
- runs in kernel with an elevated privilage

Often these happen not at the same time, triggered by I/O devices like the keyboard

Intentional exceptions that occur as the result of executing instruction, if the handler corrects it will return to the faulty instruction and retry, ex: page fault

When a virtual address is referenced that doesnt have a page on memory. (it has to be retrieved from disk)

Traps are wrapped up into functions like read(), open(), and write()

Instance of a program in execution, They have an independent logical control flow and private address space

Two flows whose execution overlap in time.

a process taking turns with other processes

two processes on different processors running at the same time

The OS sets up mappings between a processes logical memory and RAM, Processes only see memory through mapping

What library are fork and execve in

Clones the process, it's file descriptors, it's process group ID, it's memory space, pretty much everything

When fork returns 0

when fork returns the childs process ID

An unreaped child (when the parent doesn't use wait())

Allows to child to see it's own process ID

Waits for any child to end - Non-deterministic

waits for a specific child to end

What do you include to use wait

Path, arguments, null terminator

replaces code with an execution of a command line statement

higher level software form of exceptions that allow processes + kernel to interrupt other processes,
allows processes to catch interrupts

kernel forces destination process to react to signal
ignore, terminate, or handle it with a user level function

sent but not recieved, only one can exist for each type of signal

processes can block the reciept. they are delievered but no response

How do you get the process group of which the child and parent are the same

kill(pid, SIGKILL)