From 099c6116ccb11595620148cd1a321bd216d37e2b Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josharian@gmail.com>
Date: Tue, 21 Apr 2020 19:03:53 +0000
Subject: [PATCH] Revert "runtime/pprof: speed up CPU profiling shutdown"

This reverts commit 1f0738c1577a55a6b7229b821ddfe762b84771d0.

Reason for revert: This May have caused issue 38567.

Change-Id: I2afa6a9d42cb29cfad09e706fb465c57e3774abd
Reviewed-on: https://go-review.googlesource.com/c/go/+/229301
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
---
 src/runtime/pprof/pprof.go | 27 ++++++---------------------
 1 file changed, 6 insertions(+), 21 deletions(-)

diff --git a/src/runtime/pprof/pprof.go b/src/runtime/pprof/pprof.go
index b828619a86..b4f9ab8f7a 100644
--- a/src/runtime/pprof/pprof.go
+++ b/src/runtime/pprof/pprof.go
@@ -81,7 +81,6 @@ import (
 	"sort"
 	"strings"
 	"sync"
-	"sync/atomic"
 	"text/tabwriter"
 	"time"
 	"unsafe"
@@ -715,22 +714,10 @@ func (p runtimeProfile) Stack(i int) []uintptr { return p[i].Stack() }
 
 var cpu struct {
 	sync.Mutex
-	profiling uint32 // bool, accessed atomically
+	profiling bool
 	done      chan bool
 }
 
-func cpuProfiling() bool {
-	return atomic.LoadUint32(&cpu.profiling) != 0
-}
-
-func setCPUProfiling(b bool) {
-	if b {
-		atomic.StoreUint32(&cpu.profiling, 1)
-	} else {
-		atomic.StoreUint32(&cpu.profiling, 0)
-	}
-}
-
 // StartCPUProfile enables CPU profiling for the current process.
 // While profiling, the profile will be buffered and written to w.
 // StartCPUProfile returns an error if profiling is already enabled.
@@ -760,10 +747,10 @@ func StartCPUProfile(w io.Writer) error {
 		cpu.done = make(chan bool)
 	}
 	// Double-check.
-	if cpuProfiling() {
+	if cpu.profiling {
 		return fmt.Errorf("cpu profiling already in use")
 	}
-	setCPUProfiling(true)
+	cpu.profiling = true
 	runtime.SetCPUProfileRate(hz)
 	go profileWriter(w)
 	return nil
@@ -780,9 +767,7 @@ func profileWriter(w io.Writer) {
 	b := newProfileBuilder(w)
 	var err error
 	for {
-		if cpuProfiling() {
-			time.Sleep(100 * time.Millisecond)
-		}
+		time.Sleep(100 * time.Millisecond)
 		data, tags, eof := readProfile()
 		if e := b.addCPUData(data, tags); e != nil && err == nil {
 			err = e
@@ -807,10 +792,10 @@ func StopCPUProfile() {
 	cpu.Lock()
 	defer cpu.Unlock()
 
-	if !cpuProfiling() {
+	if !cpu.profiling {
 		return
 	}
-	setCPUProfiling(false)
+	cpu.profiling = false
 	runtime.SetCPUProfileRate(0)
 	<-cpu.done
 }
-- 
2.48.1