Concurrency Notes
THIS PAGE IS A VERY EARLY WORK-IN-PROGRESS.
These notes on concurrency serve as a summary/refresher/reference. Some sections may be “pedagogically out of order” in order to make it more useful as a reference.
There’s a lot of overlap between concurrency and operating systems internals, so basic concurrency is often taught within an operating systems course in undergraduate university. For this page, I aim to summarize the practical core concepts of concurrency while avoiding going into too much detail about operating systems internals. I will often assume that you already have background in Linux, systems-level programming, and operating systems internals.
Synchronization Primitives
Mutex
package main
import (
"fmt"
"sync"
"time"
)
var m sync.Mutex
var v int = 0
func producer() {
for i := 0; i < 3; i++ {
m.Lock() // Blocks until mutex is released
tmp := v + 1
time.Sleep(time.Millisecond) // Simulated "long running calculation"
fmt.Printf("%d ", tmp)
v = tmp
m.Unlock()
}
}
func main() {
go producer()
go producer()
go producer()
time.Sleep(time.Second)
fmt.Println()
}
This will print: 1 2 3 4 5 6 7 8 9.
If you remove the mutex, it prints: 1 1 1 2 2 2 3 3 3.
TODO: Hmm maybe rewrite it in C?
Semaphore
TODO
Condition Variable
TODO
Useful Concurrency Abstractions
Thread/Process Pools
TODO: Start this!
Monitors
TODO: Start this!
Readers-Writer Lock
TODO: Start this!
Channels (Golang)
TODO: Start this!
Async/Await
Async/await isn’t really a concurrency, though it gives the illusion of it.
TODO: Actually, why isn’t async/await considered concurrency? Maybe find some proper references on it.
Concurrency Bugs
Deadlock
TODO: Start this!
Implementations: Threads and Processes
TODO: Start this!
Implementations: Inter-Process Communication (IPC)
TODO: Start this!
Lock-Free Data Structures
TODO: Start this!
Non-Blocking Algorithms
TODO: Start this!
Relevant Topics Not Covered
- Interrupts (It’s more of a systems internals topic.)
TODO: Anything else? It’s a very short list…
References and Acknowledgements
I used someone’s study list as a foundation for what to study. I’m not sure if they’re comfortable with me calling them out, but you know who you are! Thanks for the study list!
References: