runtime: zeroize g->fnstart to not prevent GC of the closure

Fixes #5493.

R=golang-dev, minux.ma, iant
CC=golang-dev
https://golang.org/cl/9557043

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 4875ad87c9e6e9181602c99d90e421d8588a1f18..10170d874e181e0f6411ce9bc961151df78c4327 100644 (file)
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -1232,6 +1232,7 @@ static void
 goexit0(G *gp)
 {
        gp->status = Gdead;
+       gp->fnstart = nil;
        gp->m = nil;
        gp->lockedm = nil;
        m->curg = nil;

diff --git a/test/fixedbugs/issue5493.go b/test/fixedbugs/issue5493.go
new file mode 100644 (file)
index 0000000..fe571bc
--- /dev/null
+++ b/test/fixedbugs/issue5493.go
@@ -0,0 +1,52 @@
+// run
+
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+       "runtime"
+       "sync"
+       "sync/atomic"
+       "time"
+)
+
+const N = 10
+var count int64
+
+func run() error {
+       f1 := func() {}
+       f2 := func() {
+               func() {
+                       f1()
+               }()
+       }
+       runtime.SetFinalizer(&f1, func(f *func()) {
+               atomic.AddInt64(&count, -1)
+       })
+       go f2()
+       return nil
+}
+
+func main() {
+       count = N
+       var wg sync.WaitGroup
+       wg.Add(N)
+       for i := 0; i < N; i++ {
+               go func() {
+                       run()
+                       wg.Done()
+               }()
+       }
+       wg.Wait()
+       for i := 0; i < 2*N; i++ {
+               time.Sleep(10 * time.Millisecond)
+               runtime.GC()
+       }
+       if count != 0 {
+               panic("not all finalizers are called")
+       }
+}
+