From 55ff3f7076e9ef45f8c853eece8acf36e891d885 Mon Sep 17 00:00:00 2001
From: Rob Pike <r@golang.org>
Date: Thu, 19 Jul 2012 11:55:03 -0700
Subject: [PATCH] sync: mention that WaitGroup.Add panics Fixes #3839.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6428053
---
 src/pkg/sync/waitgroup.go      | 3 ++-
 src/pkg/sync/waitgroup_test.go | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/pkg/sync/waitgroup.go b/src/pkg/sync/waitgroup.go
index 0165b1ffb2b..bc9e738e784 100644
--- a/src/pkg/sync/waitgroup.go
+++ b/src/pkg/sync/waitgroup.go
@@ -32,10 +32,11 @@ type WaitGroup struct {
 
 // Add adds delta, which may be negative, to the WaitGroup counter.
 // If the counter becomes zero, all goroutines blocked on Wait() are released.
+// If the counter goes negative, Add panics.
 func (wg *WaitGroup) Add(delta int) {
 	v := atomic.AddInt32(&wg.counter, int32(delta))
 	if v < 0 {
-		panic("sync: negative WaitGroup count")
+		panic("sync: negative WaitGroup counter")
 	}
 	if v > 0 || atomic.LoadInt32(&wg.waiters) == 0 {
 		return
diff --git a/src/pkg/sync/waitgroup_test.go b/src/pkg/sync/waitgroup_test.go
index 34430fc2158..84c4cfc37a3 100644
--- a/src/pkg/sync/waitgroup_test.go
+++ b/src/pkg/sync/waitgroup_test.go
@@ -50,7 +50,7 @@ func TestWaitGroup(t *testing.T) {
 func TestWaitGroupMisuse(t *testing.T) {
 	defer func() {
 		err := recover()
-		if err != "sync: negative WaitGroup count" {
+		if err != "sync: negative WaitGroup counter" {
 			t.Fatalf("Unexpected panic: %#v", err)
 		}
 	}()