test.dart: Dump stack traces for child processes on timeout.

tools/testing/dart/test_runner.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 1882 matching lines @@
                 watchdogTimer.cancel();
               }
             }
           }
 
           // Close stdin so that tests that try to block on input will fail.
           process.stdin.close();
           timeoutHandler() async {
             timedOut = true;
             if (process != null) {
-              var executable, arguments;
+              var executable;
               if (io.Platform.isLinux) {
                 executable = 'eu-stack';
-                arguments = ['-p ${process.pid}'];
               } else if (io.Platform.isMacOS) {
                 // Try to print stack traces of the timed out process.
                 // `sample` is a sampling profiler but we ask it sample for 1
                 // second with a 4 second delay between samples so that we only
                 // sample the threads once.
                 executable = '/usr/bin/sample';
-                arguments = ['${process.pid}', '1', '4000', '-mayDie'];
               } else if (io.Platform.isWindows) {
                 bool is_x64 = command.executable.contains("X64") ||
                               command.executable.contains("SIMARM64");
                 executable = configuration['win_sdk_path'] +
                     "\\Debuggers\\" + (is_x64 ? "x64" : "x86") + "\\cdb.exe";
                 diagnostics.add("Using $executable to print stack traces");
-                arguments = ['-p', '${process.pid}', '-c', '!uniqstack;qd'];
+              } else {
+                diagnostics.add("Capturing stack traces on"
+                                "${io.Platform.operatingSystem} not supported");
               }
+              if (executable != null) {

[zra, 2017/02/09 22:00:46]

This is all getting complicated enough that it probably makes sense to pull this
out into a helper method.

+                var pid_list = [process.pid];
+                var lines;
+                var start_line = 0;
+                if (io.Platform.isLinux || io.Platform.isMacOS) {
+                  var result = await io.Process.run("pgrep",
+                      ["-P", "${pid_list[0]}"],
+                      runInShell: true);
+                  lines = result.stdout.split('\n');
+                } else if (io.Platform.isWindows) {
+                  var result = await io.Process.run("wmic",
+                      ["process", "where" , "(ParentProcessId=${pid_list[0]})",
+                       "get", "ProcessId"],
+                      runInShell: true);
+                  lines = result.stdout.split('\n');
+                  // Skip first line containing header "ProcessId".
+                  start_line = 1;
+                } else {
+                  assert(false);
+                }
+                if (lines.length > start_line) {
+                  for (int i = start_line; i < lines.length; ++i) {
+                    var pid = int.parse(lines[i], onError: (source) => null);
+                    if (pid != null) pid_list.add(pid);
+                  }
+                } else {
+                  diagnostics.add("Could not find child pids");
+                  diagnostics.addAll(lines);
+                }
 
-              if (executable != null) {
-                try {
-                  var result = await io.Process.run(executable, arguments);
-                  diagnostics.addAll(result.stdout.split('\n'));
-                  diagnostics.addAll(result.stderr.split('\n'));
-                } catch (error) {
-                  diagnostics.add("Unable to capture stack traces: $error");
+                diagnostics.add("Process list including children: $pid_list");
+                for (pid in pid_list) {
+                  var arguments;
+                  if (io.Platform.isLinux) {
+                    arguments = ['-p $pid'];
+                  } else if (io.Platform.isMacOS) {
+                    arguments = ['$pid', '1', '4000', '-mayDie'];
+                  } else if (io.Platform.isWindows) {
+                    arguments = ['-p', '$pid', '-c', '!uniqstack;qd'];
+                  } else {
+                    assert(false);
+                  }
+                  diagnostics.add("Trying to capture stack trace for pid $pid");
+                  try {
+                    var result = await io.Process.run(executable, arguments);
+                    diagnostics.addAll(result.stdout.split('\n'));
+                    diagnostics.addAll(result.stderr.split('\n'));
+                  } catch (error) {
+                    diagnostics.add("Unable to capture stack traces: $error");
+                  }
                 }
               }
 
               if (!process.kill()) {
                 diagnostics.add("Unable to kill ${process.pid}");
               }
             }
           }
 
           stdoutSubscription.asFuture().then(closeStdout);
@@ skipping 1314 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }