1 files changed, 580 insertions, 0 deletions
diff --git a/xpcom/tests/gtest/TestHandleWatcher.cpp b/xpcom/tests/gtest/TestHandleWatcher.cpp
new file mode 100644
index 0000000000..fd9f3ab95a
--- /dev/null
+++ b/xpcom/tests/gtest/TestHandleWatcher.cpp
@@ -0,0 +1,580 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+
+#include <minwindef.h>
+#include <handleapi.h>
+#include <synchapi.h>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ErrorNames.h"
+#include "mozilla/Result.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/SharedThreadPool.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/TaskQueue.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/WinHandleWatcher.h"
+#include "nsCOMPtr.h"
+#include "nsError.h"
+#include "nsIEventTarget.h"
+#include "nsITargetShutdownTask.h"
+#include "nsIThread.h"
+#include "nsIThreadShutdown.h"
+#include "nsITimer.h"
+#include "nsTHashMap.h"
+#include "nsThreadUtils.h"
+// #include "nscore.h"
+
+namespace details {
+static nsCString MakeTargetName(const char* name) {
+  const char* testName =
+      ::testing::UnitTest::GetInstance()->current_test_info()->name();
+  nsCString ret;
+  ret.AppendPrintf("%s: %s", testName, name);
+  return ret;
+}
+}  // namespace details
+
+using HandleWatcher = mozilla::HandleWatcher;
+
+///////////////////////////////////////////////////////////////////////
+// Error handling
+
+// nsresult_fatal_err_: auxiliary function for testing-macros.
+[[noreturn]] void nsresult_fatal_err_(const char* file, size_t line,
+                                      const char* expr, nsresult res) {
+  // implementation details from the MOZ_CRASH* family of macros
+  MOZ_Crash(file, static_cast<int>(line),
+            MOZ_CrashPrintf("%s gave nsresult %s(%" PRIX32 ")", expr,
+                            mozilla::GetStaticErrorName(res), res));
+}
+
+// UNWRAP: testing-oriented variant of Result::unwrap.
+//
+// We make no use of gtest's `ASSERT_*` family of macros, since they assume
+// that a `return;` statement is sufficient to abort the test.
+template <typename T>
+T unwrap_impl_(const char* file, size_t line, const char* expr,
+               mozilla::Result<T, nsresult> res) {
+  if (MOZ_LIKELY(res.isOk())) {
+    return res.unwrap();
+  }
+  nsresult_fatal_err_(file, line, expr, res.unwrapErr());
+}
+
+#define UNWRAP(expr) unwrap_impl_(__FILE__, __LINE__, #expr, expr)
+
+///////////////////////////////////////////////////////////////////////
+// Milliseconds()
+//
+// Convenience declaration for millisecond-based mozilla::TimeDurations.
+static mozilla::TimeDuration Milliseconds(double d) {
+  return mozilla::TimeDuration::FromMilliseconds(d);
+}
+
+///////////////////////////////////////////////////////////////////////
+// TestHandleWatcher
+//
+// GTest test fixture. Provides shared resources.
+class TestHandleWatcher : public testing::Test {
+ protected:
+  static void SetUpTestSuite() { sIsLive = true; }
+  static void TearDownTestSuite() {
+    sPool = nullptr;
+    sIsLive = false;
+  }
+
+ public:
+  static already_AddRefed<mozilla::SharedThreadPool> GetPool() {
+    AssertIsLive();
+    if (!sPool) {
+      sPool = mozilla::SharedThreadPool::Get("Test Pool"_ns);
+    }
+    return do_AddRef(sPool);
+  }
+
+ private:
+  static bool sIsLive;  // just for confirmation
+  static void AssertIsLive() {
+    MOZ_ASSERT(sIsLive,
+               "attempted to use `class TestHandleWatcher` outside test group");
+  }
+
+  static RefPtr<mozilla::SharedThreadPool> sPool;
+};
+
+/* static */
+bool TestHandleWatcher::sIsLive = false;
+/* static */
+RefPtr<mozilla::SharedThreadPool> TestHandleWatcher::sPool = nullptr;
+
+///////////////////////////////////////////////////////////////////////
+// WindowsEventObject
+//
+// Convenient interface to a Windows `event` object. (This is a synchronization
+// object that's usually the wrong thing to use.)
+struct WindowsEventObject {
+  HANDLE const handle = ::CreateEvent(nullptr, TRUE, FALSE, nullptr);
+  WindowsEventObject() = default;
+  ~WindowsEventObject() { ::CloseHandle(handle); }
+
+  WindowsEventObject(WindowsEventObject const&) = delete;
+  WindowsEventObject(WindowsEventObject&&) = delete;
+  WindowsEventObject& operator=(WindowsEventObject const&) = delete;
+  WindowsEventObject& operator=(WindowsEventObject&&) = delete;
+
+  void Set() { ::SetEvent(handle); }
+};
+
+///////////////////////////////////////////////////////////////////////
+// SpawnNewThread
+//
+nsCOMPtr<nsIThread> SpawnNewThread(const char* name) {
+  nsCOMPtr<nsIThread> thread;
+  MOZ_ALWAYS_SUCCEEDS(
+      NS_NewNamedThread(details::MakeTargetName(name), getter_AddRefs(thread)));
+  return thread;
+}
+
+///////////////////////////////////////////////////////////////////////
+// SpawnNewBackgroundQueue
+//
+// (mozilla::TaskQueue expects the supplied name to outlive the queue, so we
+// just use a static string.)
+RefPtr<mozilla::TaskQueue> SpawnNewBackgroundQueue() {
+  return mozilla::TaskQueue::Create(TestHandleWatcher::GetPool(),
+                                    "task queue for TestHandleWatcher");
+}
+
+///////////////////////////////////////////////////////////////////////
+// SpinEventLoopUntil
+//
+// Local equivalent of `mozilla::SpinEventLoopUntil`, extended with a timeout.
+//
+// Spin the current thread's event loop until either a specified predicate is
+// satisfied or a specified time-interval has passed.
+//
+struct SpinEventLoopUntilRet {
+  enum Value { Ok, TimedOut, InternalError } value;
+  bool ok() const { return value == Value::Ok; }
+  bool timedOut() const { return value == Value::TimedOut; }
+
+  MOZ_IMPLICIT SpinEventLoopUntilRet(Value v) : value(v) {}
+};
+template <typename Predicate>
+SpinEventLoopUntilRet SpinEventLoopUntil(
+    Predicate const& aPredicate,
+    mozilla::TimeDuration aDuration = Milliseconds(500)) {
+  using Value = SpinEventLoopUntilRet::Value;
+  nsIThread* currentThread = NS_GetCurrentThread();
+
+  // Set up timer.
+  bool timedOut = false;
+  auto timer = UNWRAP(NS_NewTimerWithCallback(
+      [&](nsITimer*) { timedOut = true; }, aDuration, nsITimer::TYPE_ONE_SHOT,
+      "SpinEventLoop timer", currentThread));
+  auto onExitCancelTimer = mozilla::MakeScopeExit([&] { timer->Cancel(); });
+
+  bool const ret = mozilla::SpinEventLoopUntil(
+      "TestHandleWatcher"_ns, [&] { return timedOut || aPredicate(); });
+  if (!ret) return Value::InternalError;
+  if (timedOut) return Value::TimedOut;
+  return Value::Ok;
+}
+
+// metatest for `SpinEventLoopUntil`
+TEST_F(TestHandleWatcher, SpinEventLoopUntil) {
+  auto should_fail = SpinEventLoopUntil([] { return false; }, Milliseconds(1));
+  ASSERT_TRUE(should_fail.timedOut());
+  auto should_pass = SpinEventLoopUntil([] { return true; }, Milliseconds(50));
+  ASSERT_TRUE(should_pass.ok());
+}
+
+///////////////////////////////////////////////////////////////////////
+// PingMainThread
+//
+// Post a do-nothing message to the main thread's event queue. (This will signal
+// it to wake up and check its predicate, if it's waiting for that to happen.)
+void PingMainThread() {
+  MOZ_ALWAYS_SUCCEEDS(
+      NS_DispatchToMainThread(NS_NewRunnableFunction("Ping", [] {})));
+}
+
+///////////////////////////////////////////////////////////////////////
+// Individual tests
+
+// Test basic creation and destruction.
+TEST_F(TestHandleWatcher, Trivial) { HandleWatcher hw; }
+
+// Test interaction before a Watch is created.
+TEST_F(TestHandleWatcher, Empty) {
+  HandleWatcher hw;
+  ASSERT_TRUE(hw.IsStopped());
+  hw.Stop();
+}
+
+// Start and trigger an HandleWatcher directly from the main thread.
+TEST_F(TestHandleWatcher, Simple) {
+  WindowsEventObject event;
+  HandleWatcher hw;
+
+  std::atomic<bool> run = false;
+
+  hw.Watch(
+      event.handle, NS_GetCurrentThread(),
+      NS_NewRunnableFunction("TestHandleWatcher::Simple", [&] { run = true; }));
+
+  ASSERT_FALSE(run.load());
+  event.Set();
+  // Attempt to force a race below.
+  ::Sleep(0);
+  // This should not race. The HandleWatcher doesn't execute its delegate; it
+  // just queues a mozilla::Task to do that onto our thread's event queue,
+  // and that Task hasn't been permitted to run yet.
+  ASSERT_FALSE(run.load());
+
+  ASSERT_TRUE(SpinEventLoopUntil([&] { return run.load(); }).ok());
+}
+
+// Test that calling Stop() stops the watcher.
+TEST_F(TestHandleWatcher, Stop) {
+  WindowsEventObject event;
+  HandleWatcher hw;
+  std::atomic<bool> run = false;
+
+  hw.Watch(
+      event.handle, NS_GetCurrentThread(),
+      NS_NewRunnableFunction("TestHandleWatcher::Stop", [&] { run = true; }));
+
+  ASSERT_FALSE(hw.IsStopped());
+  hw.Stop();
+  ASSERT_TRUE(hw.IsStopped());
+
+  ASSERT_TRUE(SpinEventLoopUntil([&] { return run.load(); }, Milliseconds(25))
+                  .timedOut());
+}
+
+// Test that the target's destruction stops the watch.
+TEST_F(TestHandleWatcher, TargetDestroyed) {
+  WindowsEventObject event;
+  HandleWatcher hw;
+  bool run = false;
+
+  auto queue = SpawnNewThread("target thread");
+  hw.Watch(event.handle, queue.get(),
+           NS_NewRunnableFunction("never called", [&] { run = true; }));
+
+  ASSERT_FALSE(hw.IsStopped());
+  // synchronous shutdown before destruction
+  queue->Shutdown();
+
+  ASSERT_TRUE(hw.IsStopped());
+  ASSERT_FALSE(run);
+}
+
+// Test that calling `Watch` again stops the current watch.
+TEST_F(TestHandleWatcher, Rewatch) {
+  WindowsEventObject event;
+  HandleWatcher hw;
+
+  bool b1 = false;
+  bool b2 = false;
+
+  {
+    auto queue = SpawnNewThread("target thread");
+
+    hw.Watch(event.handle, queue.get(), NS_NewRunnableFunction("b1", [&] {
+               b1 = true;
+               PingMainThread();
+             }));
+    hw.Watch(event.handle, queue.get(), NS_NewRunnableFunction("b2", [&] {
+               b2 = true;
+               PingMainThread();
+             }));
+
+    event.Set();
+
+    ASSERT_TRUE(SpinEventLoopUntil([&] { return b1 || b2; }).ok());
+    queue->Shutdown();
+  }
+  ASSERT_FALSE(b1);
+  ASSERT_TRUE(b2);
+}
+
+// Test that watching a HANDLE which is _already_ signaled still fires the
+// associated task.
+TEST_F(TestHandleWatcher, Presignalled) {
+  WindowsEventObject event;
+  HandleWatcher hw;
+
+  bool run = false;
+  event.Set();
+  hw.Watch(event.handle, NS_GetCurrentThread(),
+           NS_NewRunnableFunction("TestHandleWatcher::Presignalled",
+                                  [&] { run = true; }));
+
+  ASSERT_TRUE(SpinEventLoopUntil([&] { return run; }).ok());
+}
+
+///////////////////////////////////////////////////////////////////////
+// Systematic tests: normal activation
+//
+// Test that a handle becoming signalled on target A correctly enqueues a task
+// on target B, regardless of whether A == B.
+//
+struct ActivationTestSetup {
+  enum TargetType { Main, Side, Background };
+
+  WindowsEventObject event;
+  HandleWatcher watcher;
+
+  std::atomic<bool> run = false;
+  nsCOMPtr<nsIThread> sideThread;
+  nsCOMPtr<nsISerialEventTarget> backgroundQueue;
+
+ private:
+  nsIEventTarget* GetQueue(TargetType targetTyoe) {
+    MOZ_ASSERT(NS_IsMainThread());
+    switch (targetTyoe) {
+      case TargetType::Main:
+        return NS_GetCurrentThread();
+
+      case TargetType::Side: {
+        if (!sideThread) {
+          sideThread = SpawnNewThread("side thread");
+        }
+        return sideThread;
+      }
+
+      case TargetType::Background: {
+        if (!backgroundQueue) {
+          backgroundQueue = SpawnNewBackgroundQueue();
+        }
+        return backgroundQueue.get();
+      }
+    }
+  }
+
+  void OnSignaled() {
+    run = true;
+    // If we're not running on the main thread, it may be blocked waiting for
+    // events.
+    PingMainThread();
+  }
+
+ public:
+  void Setup(TargetType from, TargetType to) {
+    watcher.Watch(
+        event.handle, GetQueue(to),
+        NS_NewRunnableFunction("Reaction", [this] { this->OnSignaled(); }));
+
+    MOZ_ALWAYS_SUCCEEDS(GetQueue(from)->Dispatch(
+        NS_NewRunnableFunction("Action", [this] { event.Set(); })));
+  }
+
+  bool Execute() {
+    MOZ_ASSERT(NS_IsMainThread());
+    bool const spin = SpinEventLoopUntil([this] {
+                        MOZ_ASSERT(NS_IsMainThread());
+                        return run.load();
+                      }).ok();
+    return spin && watcher.IsStopped();
+  }
+
+  ~ActivationTestSetup() { watcher.Stop(); }
+};
+
+#define MOZ_HANDLEWATCHER_GTEST_FROM_TO(FROM, TO)  \
+  TEST_F(TestHandleWatcher, FROM##To##TO) {        \
+    ActivationTestSetup s;                         \
+    s.Setup(ActivationTestSetup::TargetType::FROM, \
+            ActivationTestSetup::TargetType::TO);  \
+    ASSERT_TRUE(s.Execute());                      \
+  }
+
+// Note that `Main -> Main` is subtly different from `Simple`, above: `Simple`
+// sets the event before spinning, while `Main -> Main` merely enqueues a Task
+// that will set the event during the spin.
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Main, Main);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Main, Side);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Main, Background);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Side, Main);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Side, Side);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Side, Background);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Background, Main);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Background, Side);
+MOZ_HANDLEWATCHER_GTEST_FROM_TO(Background, Background);
+
+///////////////////////////////////////////////////////////////////////
+// Ad-hoc tests: reentrancy
+//
+// Test that HandleWatcher neither deadlocks nor loses data if its release of a
+// referenced object causes the invocation of another method on HandleWatcher.
+
+// Reentrancy case 1/2: the event target.
+namespace {
+class MockEventTarget final : public nsIEventTarget {
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+ private:
+  // Map from registered shutdown tasks to whether or not they have been (or are
+  // being) executed. (This should probably guarantee some deterministic order,
+  // and also be mutex-protected; but that doesn't matter here.)
+  nsTHashMap<RefPtr<nsITargetShutdownTask>, bool> mShutdownTasks;
+  // Out-of band task to be run last at destruction time, regardless of anything
+  // else.
+  std::function<void(void)> mDeathAction;
+
+  ~MockEventTarget() {
+    for (auto& task : mShutdownTasks) {
+      task.SetData(true);
+      task.GetKey()->TargetShutdown();
+    }
+    if (mDeathAction) {
+      mDeathAction();
+    }
+  }
+
+ public:
+  // shutdown task handling
+  NS_IMETHOD RegisterShutdownTask(nsITargetShutdownTask* task) override {
+    mShutdownTasks.WithEntryHandle(task, [&](auto entry) {
+      if (entry.HasEntry()) {
+        MOZ_CRASH("attempted to double-register shutdown task");
+      }
+      entry.Insert(false);
+    });
+    return NS_OK;
+  }
+  NS_IMETHOD UnregisterShutdownTask(nsITargetShutdownTask* task) override {
+    mozilla::Maybe<bool> res = mShutdownTasks.Extract(task);
+    if (!res.isSome()) {
+      MOZ_CRASH("attempted to unregister non-registered task");
+    }
+    if (res.value()) {
+      MOZ_CRASH("attempted to unregister already-executed shutdown task");
+    }
+    return NS_OK;
+  }
+  void RegisterDeathAction(std::function<void(void)>&& f) {
+    mDeathAction = std::move(f);
+  }
+
+  // other nsIEventTarget methods (that we don't actually use)
+  NS_IMETHOD_(bool) IsOnCurrentThreadInfallible(void) { return false; }
+  NS_IMETHOD IsOnCurrentThread(bool* _retval) {
+    *_retval = false;
+    return NS_OK;
+  }
+  NS_IMETHOD Dispatch(already_AddRefed<nsIRunnable>, uint32_t) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+  NS_IMETHOD DispatchFromScript(nsIRunnable*, uint32_t) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+  NS_IMETHOD DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+};
+NS_IMPL_ISUPPORTS(MockEventTarget, nsIEventTarget)
+}  // anonymous namespace
+
+// Test that a HandleWatcher neither deadlocks nor loses data if it's invoked
+// when it releases its target.
+TEST_F(TestHandleWatcher, TargetDestructionRecurrency) {
+  WindowsEventObject e1, e2;
+  bool b1 = false, b2 = false;
+  HandleWatcher hw;
+
+  {
+    RefPtr<MockEventTarget> p = mozilla::MakeRefPtr<MockEventTarget>();
+
+    hw.Watch(e1.handle, p.get(), NS_NewRunnableFunction("first callback", [&] {
+               b1 = true;
+               PingMainThread();
+             }));
+
+    p->RegisterDeathAction([&] {
+      hw.Watch(e2.handle, mozilla::GetMainThreadSerialEventTarget(),
+               NS_NewRunnableFunction("second callback", [&] { b2 = true; }));
+    });
+  }
+
+  ASSERT_FALSE(hw.IsStopped());
+  hw.Stop();
+  ASSERT_FALSE(hw.IsStopped());  // [sic]
+
+  e1.Set();  // should do nothing
+  e2.Set();
+  ASSERT_TRUE(SpinEventLoopUntil([&] { return b1 || b2; }).ok());
+  ASSERT_FALSE(b1);
+  ASSERT_TRUE(b2);
+}
+
+// Reentrancy case 2/2: the runnable.
+namespace {
+class MockRunnable final : public nsIRunnable {
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_IMETHOD Run() override {
+    MOZ_CRASH("MockRunnable was invoked");
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+  std::function<void(void)> mDeathAction;
+
+ public:
+  void RegisterDeathAction(std::function<void(void)>&& f) {
+    mDeathAction = std::move(f);
+  }
+
+ private:
+  ~MockRunnable() {
+    if (mDeathAction) {
+      mDeathAction();
+    }
+  }
+};
+NS_IMPL_ISUPPORTS(MockRunnable, nsIRunnable)
+}  // anonymous namespace
+
+// Test that a HandleWatcher neither deadlocks nor loses data if it's invoked
+// when it releases its task.
+TEST_F(TestHandleWatcher, TaskDestructionRecurrency) {
+  WindowsEventObject e1, e2;
+  bool run = false;
+  HandleWatcher hw;
+
+  auto thread = SpawnNewBackgroundQueue();
+
+  {
+    RefPtr<MockRunnable> runnable = mozilla::MakeRefPtr<MockRunnable>();
+
+    runnable->RegisterDeathAction([&] {
+      hw.Watch(e2.handle, thread, NS_NewRunnableFunction("callback", [&] {
+                 run = true;
+                 PingMainThread();
+               }));
+    });
+
+    hw.Watch(e1.handle, thread.get(), runnable.forget());
+  }
+
+  ASSERT_FALSE(hw.IsStopped());
+  hw.Stop();
+  ASSERT_FALSE(hw.IsStopped());  // [sic]
+
+  e1.Set();
+  // give MockRunnable a chance to run (and therefore crash) if it somehow
+  // hasn't been discmnnected
+  ASSERT_TRUE(
+      SpinEventLoopUntil([&] { return false; }, Milliseconds(10)).timedOut());
+
+  e2.Set();
+  ASSERT_TRUE(SpinEventLoopUntil([&] { return run; }).ok());
+  ASSERT_TRUE(run);
+}