Is accessing different struct members in Go concurrently thread-safe?

Thread Safety of Struct Member Access in Go

When working with concurrency in Go, it's crucial to understand the thread safety of accessing different struct members.

Independent Struct Member Access

In Go, it is generally considered thread safe to access different members of a struct from different goroutines. This is because each struct member is treated as a distinct variable. Consider the following code:

type Apple struct {
    color string
    size  uint
}

func main() {
    apple := &Apple{}
    go func() {
        apple.color = "red"
    }()
    go func() {
        apple.size = 42
    }()
}

In this example, each goroutine modifies a different member of the Apple struct without causing any race conditions.

Caveats

While accessing different members of a struct is generally safe, there are some caveats to consider:

• Cache Line Contention: Although variables in a struct are separate, they may be located within the same cache line. This means that concurrent writes to adjacent members can introduce performance degradation due to cache line locking.
• Structural Changes: It's crucial to note that changing the pointer to the struct itself while concurrently writing to members is NOT thread safe. This can lead to unpredictable behavior and data corruption.

Synchronization Considerations

In scenarios where access to struct members needs to be strictly synchronized, synchronization primitives like channels or mutexes can be employed. However, this is only necessary if the specific use case introduces data race conditions or requires strict control over the order of member access.

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