Concurrency and Multi-threading Concepts

Flashcards covering key concepts from concurrency and multi-threading topics in computer science.

Once we have multiple _____ within a process, the order in which things happen is no longer entirely __________.

threads, deterministic

The basic abstraction introduced for concurrency is that of a(n) __________, which breaks the classic view of a single point of execution within a program.

thread

Code that accesses shared data in a multi-threaded program is known as a(n) __________.

critical section

Each thread in a process keeps separate _____ information, including the __________ register (which keeps track of where the program is fetching instructions from).

state, PC

All of a thread's state information is saved in a(n) _____ ______ ______, similar to the ______ ______ _______ stored for each process.

Thread Control Block, Process Control Block

Without some intentional control, multi-threaded access to shared data will lead to a(n) __________, where the results depend on the timing of the code's execution.

race condition

In multi-threaded programs, we often want some chunk of code to execute __________, without being pre-empted before completing.

atomically

__________ keeps two (or more threads) from accessing shared data at the same time, avoiding race conditions.

mutual exclusion

All threads in a process share both code and the _____ section of memory, but each thread has its own __________ (often called thread-local storage).

heap, stack

To facilitate the writing of correctly-functioning concurrent programs, the _______ provides a few useful instructions we can use to build __________ primitives, which threads can then use to coordinate access to shared resources.

hardware, synchronization

The threading API analogous to fork() is called _____ _____.

pthread_create()

Unlike a fork call, the function that creates a new thread takes a(n) __________ as an argument.

function pointer

The most basic way of accomplishing mutual exclusion when using the pthread library is to create a(n) __________, which is a variable of type __________.

mutex, pthread_mutex

Because C lacks native support for generics, the thread creation function both accepts and returns a(n) __________.

void pointer

The threading API analogous to wait() is called __________.

pthread_join()

Using a separate lock for each separate shared resource is a __________ locking strategy that can increase concurrency.

fine-grained

Above all else, a locking mechanism must guarantee __________. Otherwise, it might allow multiple threads to enter a critical section simultaneously.

mutual exclusion

To use locks in a multi-threaded program, you first declare a(n) __________ variable. For the simplest type of POSIX lock, it would be of type pthread ______

lock, mutex

You can guarantee that a block of instructions will execute __________ by disabling ______ before starting its execution.

atomically, interrupts

When moving a thread from the _______ state to the blocked state due to an unavailable lock, the OS has to add the thread to a(n) __________ so it gets a fair chance to run when the lock becomes available.

running, queue

In general, spin locks pass the _______ criterion for locking, but fail miserably in the areas of __________ and performance.

correctness, fairness

When no thread is in its corresponding ______ section, the lock is said to be __________.

critical, free

Constantly polling a flag until its value changes is called __________. It's effective but not efficient.

spin-waiting

The test-and-set instruction is often known as the __________ instruction, since it swaps the contents of a register with the contents of a memory location in a single instruction.

atomic exchange

In the context of locking, _______ means giving each thread contending for the lock a chance at acquiring it once it's free. On the other hand, if a thread never gets a chance to run, it's said to be suffering from __________.

fairness, starvation

To avoid spin waiting, a thread can voluntarily move itself from the _________ state to the __________ state by calling yield().

running, ready

Having one big lock that is used any time any critical section is accessed is be a __________ locking strategy, which can lead to inefficiency.

coarse-grained

As an alternative to spin waiting, the function that acquires a lock can move the calling thread from the _______ state to the __________ state, where it doesn't take up any CPU time until the lock becomes available.

running, blocked

When a ______ is in the critical section guarded by a particular lock, that lock should be______ by that thread.

thread, held

Every ________ section in a multi-threaded program needs to be 'protected' by a(n) __________, which provides mutual exclusion.

critical, lock

The simplest type of POSIX lock is called a(n) __________ because it is used to provide mutual exclusion between threads.

mutex

Instead of spin waiting, the function that acquires a lock can use the __________ system call to force a context switch if the flag it's waiting for has not yet changed.

yield()

When compiling a multi-threaded program (using GCC or Clang), you have to add the __________ command-line switch to ensure the correct library is linked, and other configuration changes are made.

pthread