internal/gocommand: more tweaks to DebugHangingGoCommands

As suggested by bcmills, this change increases the time
between SIGINT and SIGKILL to 5s (was 1s), and also
suppresses the process dump if SIGKILL returned
"already done".

Updates golang/go#57999
Updates golang/go#54461

Change-Id: Ie0e55a69d3bbfb4224e5f4ea272c7c2f3210e342
Reviewed-on: https://go-review.googlesource.com/c/tools/+/483215
Run-TryBot: Alan Donovan <[email protected]>
gopls-CI: kokoro <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: adonovan

internal/gocommand/invoke.go

@@ -8,6 +8,7 @@ package gocommand
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -253,7 +254,8 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) error {
 
 	// If we're interested in debugging hanging Go commands, stop waiting after a
 	// minute and panic with interesting information.
-	if DebugHangingGoCommands {
+	debug := DebugHangingGoCommands
+	if debug {
 		select {
 		case err := <-resChan:
 			return err
@@ -274,19 +276,25 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) error {
 	select {
 	case err := <-resChan:
 		return err
-	case <-time.After(time.Second):
+	case <-time.After(5 * time.Second):
+		// (We used to wait only 1s but this proved
+		// fragile on loaded builder machines.)
 	}
 
 	// Didn't shut down in response to interrupt. Kill it hard.
 	// TODO(rfindley): per advice from bcmills@, it may be better to send SIGQUIT
 	// on certain platforms, such as unix.
-	if err := cmd.Process.Kill(); err != nil && DebugHangingGoCommands {
-		// Don't panic here as this reliably fails on windows with EINVAL.
-		log.Printf("error killing the Go command: %v", err)
+	if err := cmd.Process.Kill(); err != nil && debug {
+		if errors.Is(err, os.ErrProcessDone) {
+			debug = false // no need to dump the process tree
+		} else {
+			// Don't panic here as this reliably fails on windows with EINVAL.
+			log.Printf("error killing the Go command: %v", err)
+		}
 	}
 
 	// See above: don't wait indefinitely if we're debugging hanging Go commands.
-	if DebugHangingGoCommands {
+	if debug {
 		select {
 		case err := <-resChan:
 			return err