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>

diff --git a/src/runtime/pprof/pprof.go b/src/runtime/pprof/pprof.go
index b828619a86014f9f9a5a6cc133810fa721aef4d9..b4f9ab8f7aa0a1495dde2e032512f62b26239fca 100644 (file)
--- 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
 }