Does WaitGroup.Wait() in Go Guarantee Memory Barriers?

Implications of WaitGroup.Wait() on Memory Barriers

WaitGroup.Wait() is a function in the Go programming language that blocks until the count of the WaitGroup object reaches zero. In a recent discussion on the Go forum, a question arose regarding whether WaitGroup.Wait() implies a memory barrier.

The answer to this question is yes. There is a happens-before relationship established between wg.Wait() and wg.Done(). This means that any changes made to shared variables after wg.Wait() returns will be visible to threads that previously issued wg.Done().

This holds true even if the WaitGroup is used with a single item. The underlying architectures (x86, x64, or ARM) ensure that the memory barrier is maintained.

The fact that there is no explicit mention of a memory barrier in the documentation is somewhat puzzling. However, it is important to note that happens-before relationships are not merely implied by documentation but are inherent to the language semantics and underlying hardware architecture.

This means that developers can rely on WaitGroup.Wait() to provide a consistent ordering of memory accesses, ensuring that concurrent threads can safely access shared data.

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