Do Goroutines Always Run Sequentially? Understanding Goroutine Yielding and Cooperative Scheduling

Goroutines Yielding Execution: Unlocking the Goroutine Flow

Goroutines are scheduled cooperatively, meaning they yield execution voluntarily. This cooperative scheduling approach ensures fairness by preventing any single goroutine from monopolizing the processor. However, concerns arise whether this mechanism can lead to goroutines running sequentially when execution is not yielded.

The quote from the Nindalf blog highlights this potential issue, stating that a continuously looping goroutine can starve others on the same thread. This implies that if multiple goroutines are launched, such as:

go sum(100)
go sum(200)
go sum(300)
go sum(400)

and the sum function contains only an infinite loop, the goroutines would execute one by one on a single thread. This situation would arise because the goroutines never yield execution, effectively blocking the thread.

However, the quote fails to consider recent changes in the Go runtime. Notably, the fmt.Println function call within sum could trigger other goroutines to be scheduled. Modern runtimes invoke the scheduler during function calls, introducing points where goroutines can yield execution.

If the sum function contains no function calls or external interactions, it's true that the goroutine will occupy the thread until exiting or encountering a point where execution can be yielded. This behavior emphasizes the importance of designing goroutines to avoid continuous loops without yielding points.

Ultimately, the Go runtime strives to maintain fairness and prevent starvation by allowing multiple goroutines to execute. The specific implementation may change over time, but the core principle of cooperative scheduling remains. Understanding the impact of function calls on goroutine scheduling is crucial for efficient goroutine usage.

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