From a71ca3dfbd32faf351ff68bcc26a4d5abd9b06d7 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Wed, 26 Jan 2022 16:53:50 -0500 Subject: runtime, sync, sync/atomic: document happens-before guarantees A few of these are copied from the memory model doc. Many are entirely new, following discussion on #47141. See https://research.swtch.com/gomm for background. The rule we are establishing is that each type that is meant to help synchronize a Go program should document its happens-before guarantees. For #50859. Change-Id: I947c40639b263abe67499fa74f68711a97873a39 Reviewed-on: https://go-review.googlesource.com/c/go/+/381316 Auto-Submit: Russ Cox Run-TryBot: Russ Cox Reviewed-by: Ian Lance Taylor Reviewed-by: Alan Donovan TryBot-Result: Gopher Robot Reviewed-by: Roland Shoemaker --- src/sync/map.go | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/sync/map.go') diff --git a/src/sync/map.go b/src/sync/map.go index 2fa3253429..ec529e056b 100644 --- a/src/sync/map.go +++ b/src/sync/map.go @@ -24,6 +24,13 @@ import ( // contention compared to a Go map paired with a separate Mutex or RWMutex. // // The zero Map is empty and ready for use. A Map must not be copied after first use. +// +// In the terminology of the Go memory model, Map arranges that a write operation +// “synchronizes before” any read operation that observes the effect of the write, where +// read and write operations are defined as follows. +// Load, LoadAndDelete, LoadOrStore are read operations; +// Delete, LoadAndDelete, and Store are write operations; +// and LoadOrStore is a write operation when it returns loaded set to false. type Map struct { mu Mutex -- cgit v1.3-5-g9baa