A race condition refers to an instance where more than one thread attempts to access shared data.
In this article, we will discuss the basics of implementing a mutex using the Go sync package.
Golang Sync Package
The sync package in Go provides us with tools and methods to implement synchronization tasks, such as waitgroups and mutual exclusions.
For this article, we are only interested in the mutual exclusions locks or mutex for short. The sync package provides us with two methods to implement mutex in the Go programs:
- Lock()
- Unlock()
If you place any code between the lock and unlock methods, Go programs will only allow a single thread or goroutine to access that code.
Let us take a simple program with race conditions:
import (
"fmt"
"sync"
)
var x = 1
func add(wg *sync.WaitGroup) {
x++
wg.Done()
}
func main() {
var waitgroup sync.WaitGroup
for i := 0; i < 10000; i++ {
waitgroup.Add(1)
go add(&waitgroup)
}
waitgroup.Wait()
fmt.Println(x)
}
In the previous example, we have a function that takes the value of x and increments it by 1. The function then tells the waitgroup to unblock the wait mechanism using the Done() function.
Inside the main function, we run at least 10,000 goroutines concurrently, each trying to access and change the value of x.
Since there is no deterministic order to run the goroutines, the (increment the value of x) value of x changes at every run.
To solve for the previous race condition, we can use a mutex as shown below:
import (
"fmt"
"sync"
)
var x = 1
func add(wg *sync.WaitGroup, mx *sync.Mutex) {
// lock access to this value
mx.Lock()
x++
mx.Unlock()
wg.Done()
}
func main() {
var waitgroup sync.WaitGroup
var mutex sync.Mutex
for i := 0; i < 10000; i++ {
waitgroup.Add(1)
go add(&waitgroup, &mutex)
}
waitgroup.Wait()
fmt.Println(x)
}
Here, we add mx of type sync.Mutex to the add function. Then, we lock the increment operator to allow a single goroutine at a time.
Closing
This article covered the fundamentals of implementing a mutex in Go using the sync package to fix a simple race condition. We hope you found this article helpful. Check out other Linux Hint Articles for more tips and information.
