Section 1
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In a 32/64 bit Linux system on an x86 processor, the user default space is...
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Date created
Mar 1, 2020
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Section 1
(50 cards)
In a 32/64 bit Linux system on an x86 processor, the user default space is...
3 GB/128 TB
What is channel 1?
stdout
hardware state for threads
the kernel initializing and saving registers and CPU state
wait(sem)
an attempt by the caller to decrement the semaphore counter by 1. If the counter is non-zero, the call will succeed and return immediately to the called, leaving the semaphore counter decremented by 1. If the value of the semaphore counter is already zero, then the calling thread will be placed on the semaphore block queue, and is forced to yield its core to some other thread. Also known as p(sem) and down(sem)
How many frames in 32/64 bit modes? Show math
32 bit mode: 2^32 / 2^12 = 2^20 = 1M frames 64 bit mode: 2^48 / 2^12 = 2^36 = 64G frames
How will the address space change if the process adds two more threads?
Two new stacks would be mapped to the address space
A process cannot exist unless its address space is populated by at least...
the three areas of address space (text, data, and stack)
address space for processes
a contiguous collection of byte locations, some of which are populated by some form of contiguous memory object
spinlock
Mutual exclusion mechanism in which a process executes in an infinite loop waiting for the value of a lock variable to indicate availability
Peterson's algorithm
Allows simultaneous execution of two threads, where when it's one threads "turn" to go, the other thread is released from the while loop.
signal state for threads
Ability for thread to selectively block certain synchronous signals
PID 1
systemd (formally init)
system call
An instruction that interrupts the program being executed and requests a service from the operating system.
Total Order Problems are solved using
event counters and sequencers
Single operation of sequencers
int my_tix = ticket(seq);
Sequencers
Sequencers are always initialized to zero, and will return zero to the first thread that makes the ticket() call, while subsequent calls will return monotonically increasing integers (ie. 1, 2, 3, ... , etc.) which may eventually roll from positive to negative and back
timesharing
A system in which CPU time is shared among multiple interactive users at the same time
producer
The producer's job is to generate data, put it into the buffer, and start again
Initial Thread
When a new process is created, it is populated by exactly one executable thread. The IT of a process can create new threads only within its own process
PID 2
kthreadd
A process must have a ________________ loaded at all times
executable program
consumer
the consumer is consuming the data (i.e., removing it from the buffer), one piece at a time
software state for threads (three modes)
-running in either kernel or user mode -blocking/waiting or ready -ready/waiting or running
At the lowest memory management level, an address space is a set of...
virtual page frames
threads
The execution units (elements of code that can be scheduled to a processor)
name four blocking mechanisms
-semaphores -event counters and sequencers -pthread mutex locking -pthread condition variables
UID and GID
User Identifier and Group Identifier
The Observer Reporter Problem
an observer thread and a reporter thread must keep their counter use coherent using a single pthread mutex
What is channel 2?
stderr
What happens if the last thread in a process terminates?
The process itself must terminate
Two basic functions of an event counter
- await(EC, int value); - advance(EC);
process
the unit of management in most contemporary Operating Systems such as Windows and Linux/UNIX
signal(sem)
operation is an attempt by the caller to increment the semaphore counter by 1. The call will always succeed and return to the caller. If the counter is non-zero, then there are no waiters, and the calling thread simply increments the semaphore counter by 1 and returns.If the value of the semaphore counter is zero, then the calling thread will check to see if there are any waiters. Also known as v(sem) and up(sem)
deadlock
when two or more threads of control are blocked, each waiting on a resource held by the other thread
semaphores can be logically decomposed into which two mechanisms?
an event counter mechanism and a sequencer mechanism
await(EC, int value)
if value > EC then block and yield core; else return immediately;
What is channel 0?
stdin
producer-consumer problem
The problem is to make sure that the producer won't try to add data into the buffer if it's full and that the consumer won't try to remove data from an empty buffer.
A process can change its executable program if one of its threads makes the system call ______________
execve() (or execl()/execlp())
A 4 GB address space is split between...
3 GB user private space and 1 GB shared kernel
PID 0
a kernel process, and is not visible from user space
three mutex (mutual exclusion) lock support provided by pthread library
pthread_mutex_t pthread_mutex_lock(pthread_mutex_t *) pthread_mutex_unlock(pthread_mutex_t *)
total ordering
Ordering relationship in which all elements can be compared to each other.
Event Counter
monotonic counters that are always initialized to zero, and a waiting queue (as for a semaphore)
The number of page frames in an address space depends on...
the address mode, or the current "bit system" you're in
When a process is populated by more than one thread, the co-existing threads may require...
synchronization
Partial Order Problems are solved using
only event counters
partial ordering
Ordering relationship where for certain pairs of elements in the set, one of the elements precedes the other in the ordering
semaphores
constructs that logically consist of a counter and a waiting queue
three areas of address space
text, data, and stack
Section 2
(11 cards)