test.dart: Print stack traces of all threads when a test times out

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 1836 matching lines @@
                 watchdogTimer.cancel();
               }
             }
           }
 
           // Close stdin so that tests that try to block on input will fail.
           process.stdin.close();
           void timeoutHandler() {
             timedOut = true;
             if (process != null) {
-              if (!process.kill()) {
-                DebugLogger.error("Unable to kill ${process.pid}");
-              }
+              io.Process.run('gdb',

[rmacnak, 2016/09/07 19:33:47]

Only attempt to use gdb on Linux.

[Florian Schneider, 2016/09/07 21:02:58]

Done.

+                  ['--pid=${process.pid}',
+                   '--eval-command=thread apply all bt',
+                   '--eval-command=quit'])
+              .then((result) {
+                io.stdout.write(result.stdout);
+                io.stderr.write(result.stderr);
+              })

[siva, 2016/09/07 19:55:20]

Do we also need a catchError handler here to print a diagnostic message if gdb
fails to start.

We also have to be sure that the bots have the process attach capability set
(see /etc/sysctl.d/10-ptrace.conf).

[Florian Schneider, 2016/09/07 21:02:58]

Yes. Added printing. Also, I should only invoke gdb if it is available on the
system. Is there a standard way in Dart to find if gdb is installed on a system?

[Bill Hesse, 2016/09/08 14:58:01]

I would just run "which gdb" in a subprocess, and check the return code.

+              .whenComplete(() {
+                if (!process.kill()) {
+                  DebugLogger.error("Unable to kill ${process.pid}");
+                }
+              });
             }
           }
 
           stdoutSubscription.asFuture().then(closeStdout);
           stderrSubscription.asFuture().then(closeStderr);
 
           process.exitCode.then((exitCode) {
             if (!stdoutDone || !stderrDone) {
               watchdogTimer = new Timer(MAX_STDIO_DELAY, () {
                 DebugLogger.warning(
@@ skipping 1174 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }