os: release process handle at the end of windows (*Process).Wait

Fixes #3154.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://golang.org/cl/5707052

8 files changed, 12 insertions, 11 deletions

diff --git a/src/cmd/cgo/util.go b/src/cmd/cgo/util.go
index cd7cde2b6e..a0f216614b 100644
--- a/src/cmd/cgo/util.go
+++ b/src/cmd/cgo/util.go
@@ -36,7 +36,6 @@ func run(stdin []byte, argv []string) (stdout, stderr []byte, ok bool) {
 	if err != nil {
 		fatalf("%s", err)
 	}
-	defer p.Release()
 	r0.Close()
 	w1.Close()
 	w2.Close()
diff --git a/src/cmd/godoc/main.go b/src/cmd/godoc/main.go
index e5717f8005..ee905bb7a0 100644
--- a/src/cmd/godoc/main.go
+++ b/src/cmd/godoc/main.go
@@ -99,7 +99,6 @@ func exec(rw http.ResponseWriter, args []string) (status int) {
 		log.Printf("os.StartProcess(%q): %v", bin, err)
 		return 2
 	}
-	defer p.Release()
 
 	var buf bytes.Buffer
 	io.Copy(&buf, r)
diff --git a/src/pkg/net/http/triv.go b/src/pkg/net/http/triv.go
index c88a0fbce7..269af0ca3d 100644
--- a/src/pkg/net/http/triv.go
+++ b/src/pkg/net/http/triv.go
@@ -108,7 +108,6 @@ func DateServer(rw http.ResponseWriter, req *http.Request) {
 		fmt.Fprintf(rw, "fork/exec: %s\n", err)
 		return
 	}
-	defer p.Release()
 	io.Copy(rw, r)
 	wait, err := p.Wait(0)
 	if err != nil {
diff --git a/src/pkg/os/doc.go b/src/pkg/os/doc.go
index ef857c0429..546f864714 100644
--- a/src/pkg/os/doc.go
+++ b/src/pkg/os/doc.go
@@ -11,6 +11,13 @@ func FindProcess(pid int) (p *Process, err error) {
 	return findProcess(pid)
 }
 
+// Release releases any resources associated with the Process p,
+// rendering it unusable in the future.
+// Release only needs to be called if Wait is not.
+func (p *Process) Release() error {
+	return p.release()
+}
+
 // Hostname returns the host name reported by the kernel.
 func Hostname() (name string, err error) {
 	return hostname()
diff --git a/src/pkg/os/exec_plan9.go b/src/pkg/os/exec_plan9.go
index 1c9e2b997f..a941d12660 100644
--- a/src/pkg/os/exec_plan9.go
+++ b/src/pkg/os/exec_plan9.go
@@ -94,8 +94,7 @@ func (p *Process) Wait() (ps *ProcessState, err error) {
 	return ps, nil
 }
 
-// Release releases any resources associated with the Process.
-func (p *Process) Release() error {
+func (p *Process) release() error {
 	// NOOP for Plan 9.
 	p.Pid = -1
 	// no need for a finalizer anymore
diff --git a/src/pkg/os/exec_unix.go b/src/pkg/os/exec_unix.go
index 8d000e9ef1..3f89fe8238 100644
--- a/src/pkg/os/exec_unix.go
+++ b/src/pkg/os/exec_unix.go
@@ -51,8 +51,7 @@ func (p *Process) Signal(sig Signal) error {
 	return nil
 }
 
-// Release releases any resources associated with the Process.
-func (p *Process) Release() error {
+func (p *Process) release() error {
 	// NOOP for unix.
 	p.Pid = -1
 	// no need for a finalizer anymore
diff --git a/src/pkg/os/exec_windows.go b/src/pkg/os/exec_windows.go
index dab0dc9757..3d07ab7c92 100644
--- a/src/pkg/os/exec_windows.go
+++ b/src/pkg/os/exec_windows.go
@@ -14,6 +14,7 @@ import (
 
 // Wait waits for the Process to exit or stop, and then returns a
 // ProcessState describing its status and an error, if any.
+// Wait releases any resources associated with the Process.
 func (p *Process) Wait() (ps *ProcessState, err error) {
 	s, e := syscall.WaitForSingleObject(syscall.Handle(p.handle), syscall.INFINITE)
 	switch s {
@@ -30,6 +31,7 @@ func (p *Process) Wait() (ps *ProcessState, err error) {
 		return nil, NewSyscallError("GetExitCodeProcess", e)
 	}
 	p.done = true
+	defer p.Release()
 	return &ProcessState{p.Pid, syscall.WaitStatus{Status: s, ExitCode: ec}, new(syscall.Rusage)}, nil
 }
 
@@ -46,8 +48,7 @@ func (p *Process) Signal(sig Signal) error {
 	return syscall.Errno(syscall.EWINDOWS)
 }
 
-// Release releases any resources associated with the Process.
-func (p *Process) Release() error {
+func (p *Process) release() error {
 	if p.handle == uintptr(syscall.InvalidHandle) {
 		return syscall.EINVAL
 	}
diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
index 02f75b2a73..d1e241f006 100644
--- a/src/pkg/os/os_test.go
+++ b/src/pkg/os/os_test.go
@@ -530,7 +530,6 @@ func exec(t *testing.T, dir, cmd string, args []string, expect string) {
 	if err != nil {
 		t.Fatalf("StartProcess: %v", err)
 	}
-	defer p.Release()
 	w.Close()
 
 	var b bytes.Buffer
@@ -848,7 +847,6 @@ func run(t *testing.T, cmd []string) string {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer p.Release()
 	w.Close()
 
 	var b bytes.Buffer