From dada467fc688ef5970bf4af30c2644c0d2ccdb54 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Thu, 19 Jul 2018 13:23:32 -0400
Subject: [PATCH] cmd/go/internal/par: actually make par.Work run things in
 parallel

This was an unfortunate debugging print introduced
while working on the unfortunately large CL 123576.
At least now we're done with that awfulness.

Change-Id: Ib83db59382a799f649832d22d3c6f039d2ef9d2c
Reviewed-on: https://go-review.googlesource.com/125015
Reviewed-by: Bryan C. Mills <bcmills@google.com>
---
 src/cmd/go/internal/par/work.go      |  1 -
 src/cmd/go/internal/par/work_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/cmd/go/internal/par/work.go b/src/cmd/go/internal/par/work.go
index 6543f1a35c..a568c86f60 100644
--- a/src/cmd/go/internal/par/work.go
+++ b/src/cmd/go/internal/par/work.go
@@ -55,7 +55,6 @@ func (w *Work) Do(n int, f func(item interface{})) {
 	if n < 1 {
 		panic("par.Work.Do: n < 1")
 	}
-	n = 1
 	if w.running >= 1 {
 		panic("par.Work.Do: already called Do")
 	}
diff --git a/src/cmd/go/internal/par/work_test.go b/src/cmd/go/internal/par/work_test.go
index 71c0395d3b..53a715ea81 100644
--- a/src/cmd/go/internal/par/work_test.go
+++ b/src/cmd/go/internal/par/work_test.go
@@ -7,6 +7,7 @@ package par
 import (
 	"sync/atomic"
 	"testing"
+	"time"
 )
 
 func TestWork(t *testing.T) {
@@ -30,6 +31,30 @@ func TestWork(t *testing.T) {
 	}
 }
 
+func TestWorkParallel(t *testing.T) {
+	var w Work
+
+	for tries := 0; tries < 10; tries++ {
+		const N = 100
+		for i := 0; i < N; i++ {
+			w.Add(i)
+		}
+		start := time.Now()
+		var n int32
+		w.Do(N, func(x interface{}) {
+			time.Sleep(1 * time.Millisecond)
+			atomic.AddInt32(&n, +1)
+		})
+		if n != N {
+			t.Fatalf("par.Work.Do did not do all the work")
+		}
+		if time.Since(start) < N/2*time.Millisecond {
+			return
+		}
+	}
+	t.Fatalf("par.Work.Do does not seem to be parallel")
+}
+
 func TestCache(t *testing.T) {
 	var cache Cache
 
-- 
2.50.0