test: fix flaky test for issue24491

runtime.GC() doesn't guarantee the finalizer has run, so use a channel
instead to make sure finalizer was run in call to "after()".

Fixes #41361

Change-Id: I69c801e29aea49757ea72c52e8db13239de19ddc
Reviewed-on: https://go-review.googlesource.com/c/go/+/254401
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>

diff --git a/test/fixedbugs/issue24491b.go b/test/fixedbugs/issue24491b.go
index 5f4a2f233e0824ac94e636086c344e404f36b103..142d798500b76208bde23e09567511d6c0380171 100644 (file)
--- a/test/fixedbugs/issue24491b.go
+++ b/test/fixedbugs/issue24491b.go
@@ -11,15 +11,14 @@ package main
 
 import (
        "runtime"
-       "sync/atomic"
        "unsafe"
 )
 
-var done uint32
+var done = make(chan bool)
 
 func setup() unsafe.Pointer {
        s := "ok"
-       runtime.SetFinalizer(&s, func(p *string) { atomic.StoreUint32(&done, 1) })
+       runtime.SetFinalizer(&s, func(p *string) { close(done) })
        return unsafe.Pointer(&s)
 }
 
@@ -27,17 +26,18 @@ func setup() unsafe.Pointer {
 //go:uintptrescapes
 func before(p uintptr) int {
        runtime.GC()
-       if atomic.LoadUint32(&done) != 0 {
+       select {
+       case <-done:
                panic("GC early")
+       default:
        }
        return 0
 }
 
 func after() int {
        runtime.GC()
-       if atomic.LoadUint32(&done) == 0 {
-               panic("GC late")
-       }
+       runtime.GC()
+       <-done
        return 0
 }