Identify the hung thread using the Wait Chain Traversal API

base/win/wait_chain_unittest.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 <string>
+
+#include "base/bind.h"
+#include "base/command_line.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/test/multiprocess_test.h"
+#include "base/threading/simple_thread.h"
+#include "base/win/win_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/multiprocess_func_list.h"
+
+namespace base {
+namespace win {
+
+namespace {
+
+// Appends |handle| as a command line switch.
+void AppendSwitchHandle(CommandLine* command_line,
+                        StringPiece switch_name,
+                        HANDLE handle) {
+  command_line->AppendSwitchASCII(switch_name.as_string(),
+                                  UintToString(HandleToUint32(handle)));
+}
+
+// Retrieves the |handle| associated to |switch_name| from the command line.
+ScopedHandle GetSwitchValueHandle(CommandLine* command_line,
+                                  StringPiece switch_name) {
+  std::string switch_string =
+      command_line->GetSwitchValueASCII(switch_name.as_string());
+  unsigned int switch_uint = 0;
+  if (switch_string.empty() || !StringToUint(switch_string, &switch_uint)) {
+    DLOG(ERROR) << "Missing or invalid " << switch_name << " argument.";
+    return ScopedHandle();
+  }
+  return ScopedHandle(reinterpret_cast<HANDLE>(switch_uint));
+}
+
+// Helper function to create a mutex.
+ScopedHandle CreateMutex(bool inheritable) {
+  SECURITY_ATTRIBUTES security_attributes = {sizeof(SECURITY_ATTRIBUTES),
+                                             nullptr, inheritable};
+  return ScopedHandle(::CreateMutex(&security_attributes, FALSE, NULL));
+}
+
+// Helper function to create an event.
+ScopedHandle CreateEvent(bool inheritable) {
+  SECURITY_ATTRIBUTES security_attributes = {sizeof(SECURITY_ATTRIBUTES),
+                                             nullptr, inheritable};
+  return ScopedHandle(
+      ::CreateEvent(&security_attributes, FALSE, FALSE, nullptr));
+}
+
+// Helper thread class that runs the callback then stops.
+class SingleTaskThread : public SimpleThread {
+ public:
+  explicit SingleTaskThread(const Closure& task)
+      : SimpleThread("WaitChainTest SingleTaskThread"), task_(task) {}
+
+  void Run() override { task_.Run(); }
+
+ private:
+  Closure task_;
+
+  DISALLOW_COPY_AND_ASSIGN(SingleTaskThread);
+};
+
+// Helper thread to cause a deadlock by acquiring 2 mutexes in a given order.
+class DeadlockThread : public SimpleThread {
+ public:
+  DeadlockThread(HANDLE mutex_1, HANDLE mutex_2)
+      : SimpleThread("WaitChainTest DeadlockThread"),
+        wait_event_(CreateEvent(false)),
+        mutex_acquired_event_(CreateEvent(false)),
+        mutex_1_(mutex_1),
+        mutex_2_(mutex_2) {}
+
+  void Run() override {
+    // Acquire the mutex then signal the main thread.
+    EXPECT_EQ(WAIT_OBJECT_0, ::WaitForSingleObject(mutex_1_, INFINITE));
+    EXPECT_TRUE(::SetEvent(mutex_acquired_event_.Get()));
+
+    // Wait until both threads are holding their mutex before trying to acquire
+    // the other one.
+    EXPECT_EQ(WAIT_OBJECT_0,
+              ::WaitForSingleObject(wait_event_.Get(), INFINITE));
+
+    // To unblock the deadlock, one of the threads will get terminated (via
+    // TerminateThread()) without releasing the mutex. This causes the other
+    // thread to wake up with WAIT_ABANDONED.
+    EXPECT_EQ(WAIT_ABANDONED, ::WaitForSingleObject(mutex_2_, INFINITE));
+  }
+
+  // Blocks until a mutex is acquired.
+  void WaitForMutexAcquired() {
+    EXPECT_EQ(WAIT_OBJECT_0,
+              ::WaitForSingleObject(mutex_acquired_event_.Get(), INFINITE));
+  }
+
+  // Signal the thread to acquire the second mutex.
+  void SignalToAcquireMutex() { EXPECT_TRUE(::SetEvent(wait_event_.Get())); }
+
+  // Terminates the thread.
+  bool Terminate() {
+    ScopedHandle thread_handle(::OpenThread(THREAD_TERMINATE, FALSE, tid()));
+    return ::TerminateThread(thread_handle.Get(), 0);
+  }
+
+ private:
+  ScopedHandle wait_event_;
+  ScopedHandle mutex_acquired_event_;
+
+  // The 2 mutex to acquire.
+  HANDLE mutex_1_;
+  HANDLE mutex_2_;
+
+  DISALLOW_COPY_AND_ASSIGN(DeadlockThread);
+};
+
+// Creates a thread that joins |thread_to_join| and then terminates when it
+// finishes execution.
+std::unique_ptr<SingleTaskThread> CreateJoiningThread(
+    SimpleThread* thread_to_join) {
+  std::unique_ptr<SingleTaskThread> thread(new SingleTaskThread(
+      Bind(&SimpleThread::Join, Unretained(thread_to_join))));
+  thread->Start();
+
+  return thread;
+}
+
+// Creates a thread that calls WaitForSingleObject() on the handle and then
+// terminates when it unblocks.
+std::unique_ptr<SingleTaskThread> CreateWaitingThread(HANDLE handle) {
+  std::unique_ptr<SingleTaskThread> thread(new SingleTaskThread(
+      Bind(IgnoreResult(&::WaitForSingleObject), handle, INFINITE)));
+  thread->Start();
+
+  return thread;
+}
+
+// Creates a thread that blocks on |mutex_2| after acquiring |mutex_1|.
+std::unique_ptr<DeadlockThread> CreateDeadlockThread(HANDLE mutex_1,
+                                                     HANDLE mutex_2) {
+  std::unique_ptr<DeadlockThread> thread(new DeadlockThread(mutex_1, mutex_2));
+  thread->Start();
+
+  // Wait until the first mutex is acquired before returning.
+  thread->WaitForMutexAcquired();
+
+  return thread;
+}
+
+// Child process to test the cross-process capability of the WCT api.
+// This process will simulate a hang while holding a mutex that the parent
+// process is waiting on.
+MULTIPROCESS_TEST_MAIN(WaitChainTestProc) {
+  CommandLine* command_line = CommandLine::ForCurrentProcess();
+
+  ScopedHandle mutex = GetSwitchValueHandle(command_line, "mutex");
+  CHECK(mutex.IsValid());
+
+  ScopedHandle sync_event(GetSwitchValueHandle(command_line, "sync_event"));
+  CHECK(sync_event.IsValid());
+
+  // Acquire mutex.
+  CHECK(::WaitForSingleObject(mutex.Get(), INFINITE) == WAIT_OBJECT_0);
+
+  // Signal back to the parent process that the mutex is hold.
+  CHECK(::SetEvent(sync_event.Get()));
+
+  // Wait on a signal from the parent process before terminating.
+  CHECK(::WaitForSingleObject(sync_event.Get(), INFINITE) == WAIT_OBJECT_0);
+
+  return 0;
+}
+
+// Start a child process and passes the |mutex| and the |sync_event| to the
+// command line.
+Process StartChildProcess(HANDLE mutex, HANDLE sync_event) {
+  CommandLine command_line = GetMultiProcessTestChildBaseCommandLine();
+
+  AppendSwitchHandle(&command_line, "mutex", mutex);
+  AppendSwitchHandle(&command_line, "sync_event", sync_event);
+
+  LaunchOptions options;
+  HandlesToInheritVector handle_vector;
+  handle_vector.push_back(mutex);
+  handle_vector.push_back(sync_event);
+  options.handles_to_inherit = &handle_vector;
+  return SpawnMultiProcessTestChild("WaitChainTestProc", command_line, options);
+}
+
+// Returns true if the |wait_chain| is an alternating sequence of thread objects
+// and synchronization objects.
+bool WaitChainStructureIsCorrect(const WaitChainNodeVector& wait_chain) {
+  // Checks thread objects.
+  for (size_t i = 0; i < wait_chain.size(); i += 2) {
+    if (wait_chain[i].ObjectType != WctThreadType)
+      return false;
+  }
+
+  // Check synchronization objects.
+  for (size_t i = 1; i < wait_chain.size(); i += 2) {
+    if (wait_chain[i].ObjectType == WctThreadType)
+      return false;
+  }
+  return true;
+}
+
+// Returns true if the |wait_chain| goes through more than 1 process.
+bool WaitChainIsCrossProcess(const WaitChainNodeVector& wait_chain) {
+  if (wait_chain.size() == 0)
+    return false;
+
+  // Just check that the process id changes somewhere in the chain.
+  // Note: ThreadObjects are every 2 nodes.
+  DWORD first_process = wait_chain[0].ThreadObject.ProcessId;
+  for (size_t i = 2; i < wait_chain.size(); i += 2) {
+    if (first_process != wait_chain[i].ThreadObject.ProcessId)
+      return true;
+  }
+  return false;
+}
+
+}  // namespace
+
+// Creates 2 threads that acquire their designated mutex and then try to
+// acquire each others' mutex to cause a deadlock.
+TEST(WaitChainTest, Deadlock) {
+  // 2 mutexes are needed to get a deadlock.
+  ScopedHandle mutex_1 = CreateMutex(false);
+  ASSERT_TRUE(mutex_1.IsValid());
+  ScopedHandle mutex_2 = CreateMutex(false);
+  ASSERT_TRUE(mutex_2.IsValid());
+
+  std::unique_ptr<DeadlockThread> deadlock_thread_1 =
+      CreateDeadlockThread(mutex_1.Get(), mutex_2.Get());
+  std::unique_ptr<DeadlockThread> deadlock_thread_2 =
+      CreateDeadlockThread(mutex_2.Get(), mutex_1.Get());
+
+  // Signal the threads to try to acquire the other mutex.
+  deadlock_thread_1->SignalToAcquireMutex();
+  deadlock_thread_2->SignalToAcquireMutex();
+  // Sleep to make sure the 2 threads got a chance to execute.
+  Sleep(10);
+
+  // Create a few waiting threads to get a longer wait chain.
+  std::unique_ptr<SingleTaskThread> waiting_thread_1 =
+      CreateJoiningThread(deadlock_thread_1.get());
+  std::unique_ptr<SingleTaskThread> waiting_thread_2 =
+      CreateJoiningThread(waiting_thread_1.get());
+
+  WaitChainNodeVector wait_chain;
+  bool is_deadlock;
+  ASSERT_TRUE(
+      GetThreadWaitChain(waiting_thread_2->tid(), &wait_chain, &is_deadlock));
+
+  EXPECT_EQ(9U, wait_chain.size());
+  EXPECT_TRUE(is_deadlock);
+  EXPECT_TRUE(WaitChainStructureIsCorrect(wait_chain));
+  EXPECT_FALSE(WaitChainIsCrossProcess(wait_chain));
+
+  ASSERT_TRUE(deadlock_thread_1->Terminate());
+
+  // The SimpleThread API expect Join() to be called before destruction.
+  deadlock_thread_2->Join();
+  waiting_thread_2->Join();
+}
+
+// Creates a child process that acquires a mutex and then blocks. A chain of
+// threads then blocks on that mutex.
+TEST(WaitChainTest, CrossProcess) {
+  ScopedHandle mutex = CreateMutex(true);
+  ASSERT_TRUE(mutex.IsValid());
+  ScopedHandle sync_event = CreateEvent(true);
+  ASSERT_TRUE(sync_event.IsValid());
+
+  Process child_process = StartChildProcess(mutex.Get(), sync_event.Get());
+  ASSERT_TRUE(child_process.IsValid());
+
+  // Wait for the child process to signal when it's holding the mutex.
+  EXPECT_EQ(WAIT_OBJECT_0, ::WaitForSingleObject(sync_event.Get(), INFINITE));
+
+  // Create a few waiting threads to get a longer wait chain.
+  std::unique_ptr<SingleTaskThread> waiting_thread_1 =
+      CreateWaitingThread(mutex.Get());
+  std::unique_ptr<SingleTaskThread> waiting_thread_2 =
+      CreateJoiningThread(waiting_thread_1.get());
+  std::unique_ptr<SingleTaskThread> waiting_thread_3 =
+      CreateJoiningThread(waiting_thread_2.get());
+
+  WaitChainNodeVector wait_chain;
+  bool is_deadlock;
+  ASSERT_TRUE(
+      GetThreadWaitChain(waiting_thread_3->tid(), &wait_chain, &is_deadlock));
+
+  EXPECT_EQ(7U, wait_chain.size());
+  EXPECT_FALSE(is_deadlock);
+  EXPECT_TRUE(WaitChainStructureIsCorrect(wait_chain));
+  EXPECT_TRUE(WaitChainIsCrossProcess(wait_chain));
+
+  // Unblock child process and wait for it to terminate.
+  ASSERT_TRUE(::SetEvent(sync_event.Get()));
+  ASSERT_TRUE(child_process.WaitForExit(nullptr));
+
+  // The SimpleThread API expect Join() to be called before destruction.
+  waiting_thread_3->Join();
+}
+
+}  // namespace win
+}  // namespace base