Identify the hung thread using the Wait Chain Traversal API

base/win/wait_chain.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/win/wait_chain.h"
+
+#include <memory>
+
+#include "base/logging.h"
+#include "base/strings/stringprintf.h"
+
+namespace base {
+namespace win {
+
+namespace {
+
+// Helper deleter to hold a HWCT into a unique_ptr.
+struct WaitChainSessionDeleter {
+  using pointer = HWCT;
+  void operator()(HWCT session_handle) {

[grt (UTC plus 2), 2016/04/12 14:31:12]

const methods

[Patrick Monette, 2016/04/12 19:13:00]

Done.

+    ::CloseThreadWaitChainSession(session_handle);
+  }
+};
+using ScopedWaitChainSessionHandle =

[grt (UTC plus 2), 2016/04/12 14:31:12]

nit: blank line before this

[Patrick Monette, 2016/04/12 19:13:00]

Done.

+    std::unique_ptr<HWCT, WaitChainSessionDeleter>;
+
+const wchar_t* WctObjectTypeToString(WCT_OBJECT_TYPE type) {
+  switch (type) {
+    case WctCriticalSectionType:
+      return L"CriticalSection";
+    case WctSendMessageType:
+      return L"SendMessage";
+    case WctMutexType:
+      return L"Mutex";
+    case WctAlpcType:
+      return L"Alpc";
+    case WctComType:
+      return L"Com";
+    case WctThreadWaitType:
+      return L"ThreadWait";
+    case WctProcessWaitType:
+      return L"ProcessWait";
+    case WctThreadType:
+      return L"Thread";
+    case WctComActivationType:
+      return L"ComActivation";
+    case WctUnknownType:
+      return L"Unknown";
+    default:

[grt (UTC plus 2), 2016/04/12 14:31:12]

can you leave off the "default" case so that there's a compiler error in the
event that new enum values are added?

[Patrick Monette, 2016/04/12 19:13:00]

Done.

+      NOTREACHED();
+      return L"";
+  }
+}
+
+const wchar_t* WctObjectStatusToString(WCT_OBJECT_STATUS status) {
+  switch (status) {
+    case WctStatusNoAccess:
+      return L"NoAccess";
+    case WctStatusRunning:
+      return L"Running";
+    case WctStatusBlocked:
+      return L"Blocked";
+    case WctStatusPidOnly:
+      return L"PidOnly";
+    case WctStatusPidOnlyRpcss:
+      return L"PidOnlyRpcss";
+    case WctStatusOwned:
+      return L"Owned";
+    case WctStatusNotOwned:
+      return L"NotOwned";
+    case WctStatusAbandoned:
+      return L"Abandoned";
+    case WctStatusUnknown:
+      return L"Unknown";
+    case WctStatusError:
+      return L"Error";
+    default:

[grt (UTC plus 2), 2016/04/12 14:31:12]

same here?

[Patrick Monette, 2016/04/12 19:13:00]

Done.

+      NOTREACHED();
+      return L"";
+  }
+}
+
+}  // namespace
+
+bool GetThreadWaitChain(DWORD thread_id,
+                        WaitChain* wait_chain,
+                        bool* is_deadlock) {
+  DCHECK(wait_chain);
+  DCHECK(is_deadlock);
+
+  // Open a synchronous session.
+  ScopedWaitChainSessionHandle session_handle(
+      ::OpenThreadWaitChainSession(0, nullptr));
+  if (!session_handle) {
+    DPLOG(ERROR) << "Failed to create the Wait Chain session";
+    return false;
+  }
+
+  DWORD nb_nodes = WCT_MAX_NODE_COUNT;
+  wait_chain->resize(nb_nodes);
+  BOOL is_cycle;
+  if (!::GetThreadWaitChain(session_handle.get(), NULL, 0, thread_id, &nb_nodes,
+                            wait_chain->data(), &is_cycle)) {
+    DPLOG(ERROR) << "Failed to get the thread wait chain";
+    return false;
+  }
+
+  *is_deadlock = is_cycle ? true : false;
+  wait_chain->resize(nb_nodes);
+
+  return true;
+}
+
+std::wstring WaitChainNodeToString(const WAITCHAIN_NODE_INFO& node) {
+  if (node.ObjectType == WctThreadType) {
+    return base::StringPrintf(L"Thread %d in process %d with status %ls",
+                              node.ThreadObject.ThreadId,
+                              node.ThreadObject.ProcessId,
+                              WctObjectStatusToString(node.ObjectStatus));
+  } else {
+    return base::StringPrintf(L"Lock of type %ls with status %ls",
+                              WctObjectTypeToString(node.ObjectType),
+                              WctObjectStatusToString(node.ObjectStatus));
+  }
+}
+
+}  // namespace win
+}  // namespace base