Parallelism

About

Is when two tasks can run each on a separate physical core, meaning they will run at the same time.

They will run in parallel unless they share the same resource. (e.g file, printer, etc)

Multiple threads handling the same resource at the same time is messy (may lead to race conditions), so this is where Mutex comes to help.

Race Condition

Is when multiple threads compete to access the same resource.

Without knowing which will access first, it can lead to non-deterministic or unexpected results.

Mutex (Locks)

Is a flag to signal exclusivity on a resouce.

The thread that access first will signal the resource to be "used", so that subsequent threads access will wait until the resource is "free".

Dead Locks

Are when threads forget or don't handle the removal of the "used" flag from the resources.

So they will forever wait the flag clearance.

Blocking I/O

Is when a thread will stay running until it finishes its operation involving an I/O resource. (e.g writing to disk, or using network connections)

Assynchronous I/O deals with these blocks over I/O. (An event is emitted on the I/O finish, so this way the thread doesn't need to synchronouly wait for it)