1 files changed, 378 insertions, 0 deletions
diff --git a/dom/workers/WorkerThread.cpp b/dom/workers/WorkerThread.cpp
new file mode 100644
index 0000000000..b6f8674343
--- /dev/null
+++ b/dom/workers/WorkerThread.cpp
@@ -0,0 +1,378 @@
+/* -*- 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 "WorkerThread.h"
+
+#include <utility>
+#include "WorkerPrivate.h"
+#include "WorkerRunnable.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/EventQueue.h"
+#include "mozilla/MacroForEach.h"
+#include "mozilla/NotNull.h"
+#include "mozilla/PerformanceCounter.h"
+#include "mozilla/ThreadEventQueue.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/ipc/BackgroundChild.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
+#include "nsICancelableRunnable.h"
+#include "nsIEventTarget.h"
+#include "nsIRunnable.h"
+#include "nsIThreadInternal.h"
+#include "nsString.h"
+#include "prthread.h"
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom {
+
+namespace {
+
+// The C stack size. We use the same stack size on all platforms for
+// consistency.
+//
+// Note: Our typical equation of 256 machine words works out to 2MB on 64-bit
+// platforms. Since that works out to the size of a VM huge page, that can
+// sometimes lead to an OS allocating an entire huge page for the stack at once.
+// To avoid this, we subtract the size of 2 pages, to be safe.
+const uint32_t kWorkerStackSize = 256 * sizeof(size_t) * 1024 - 8192;
+
+}  // namespace
+
+WorkerThreadFriendKey::WorkerThreadFriendKey() {
+  MOZ_COUNT_CTOR(WorkerThreadFriendKey);
+}
+
+WorkerThreadFriendKey::~WorkerThreadFriendKey() {
+  MOZ_COUNT_DTOR(WorkerThreadFriendKey);
+}
+
+class WorkerThread::Observer final : public nsIThreadObserver {
+  WorkerPrivate* mWorkerPrivate;
+
+ public:
+  explicit Observer(WorkerPrivate* aWorkerPrivate)
+      : mWorkerPrivate(aWorkerPrivate) {
+    MOZ_ASSERT(aWorkerPrivate);
+    aWorkerPrivate->AssertIsOnWorkerThread();
+  }
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+ private:
+  ~Observer() { mWorkerPrivate->AssertIsOnWorkerThread(); }
+
+  NS_DECL_NSITHREADOBSERVER
+};
+
+WorkerThread::WorkerThread(ConstructorKey)
+    : nsThread(
+          MakeNotNull<ThreadEventQueue*>(MakeUnique<mozilla::EventQueue>()),
+          nsThread::NOT_MAIN_THREAD, {.stackSize = kWorkerStackSize}),
+      mLock("WorkerThread::mLock"),
+      mWorkerPrivateCondVar(mLock, "WorkerThread::mWorkerPrivateCondVar"),
+      mWorkerPrivate(nullptr),
+      mOtherThreadsDispatchingViaEventTarget(0)
+#ifdef DEBUG
+      ,
+      mAcceptingNonWorkerRunnables(true)
+#endif
+{
+}
+
+WorkerThread::~WorkerThread() {
+  MOZ_ASSERT(!mWorkerPrivate);
+  MOZ_ASSERT(!mOtherThreadsDispatchingViaEventTarget);
+  MOZ_ASSERT(mAcceptingNonWorkerRunnables);
+}
+
+// static
+SafeRefPtr<WorkerThread> WorkerThread::Create(
+    const WorkerThreadFriendKey& /* aKey */) {
+  SafeRefPtr<WorkerThread> thread =
+      MakeSafeRefPtr<WorkerThread>(ConstructorKey());
+  if (NS_FAILED(thread->Init("DOM Worker"_ns))) {
+    NS_WARNING("Failed to create new thread!");
+    return nullptr;
+  }
+
+  return thread;
+}
+
+void WorkerThread::SetWorker(const WorkerThreadFriendKey& /* aKey */,
+                             WorkerPrivate* aWorkerPrivate) {
+  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
+
+  if (aWorkerPrivate) {
+    {
+      MutexAutoLock lock(mLock);
+
+      MOZ_ASSERT(!mWorkerPrivate);
+      MOZ_ASSERT(mAcceptingNonWorkerRunnables);
+
+      mWorkerPrivate = aWorkerPrivate;
+#ifdef DEBUG
+      mAcceptingNonWorkerRunnables = false;
+#endif
+    }
+
+    mObserver = new Observer(aWorkerPrivate);
+    MOZ_ALWAYS_SUCCEEDS(AddObserver(mObserver));
+  } else {
+    MOZ_ALWAYS_SUCCEEDS(RemoveObserver(mObserver));
+    mObserver = nullptr;
+
+    {
+      MutexAutoLock lock(mLock);
+
+      MOZ_ASSERT(mWorkerPrivate);
+      MOZ_ASSERT(!mAcceptingNonWorkerRunnables);
+      // mOtherThreadsDispatchingViaEventTarget can still be non-zero here
+      // because WorkerThread::Dispatch isn't atomic so a thread initiating
+      // dispatch can have dispatched a runnable at this thread allowing us to
+      // begin shutdown before that thread gets a chance to decrement
+      // mOtherThreadsDispatchingViaEventTarget back to 0.  So we need to wait
+      // for that.
+      while (mOtherThreadsDispatchingViaEventTarget) {
+        mWorkerPrivateCondVar.Wait();
+      }
+
+#ifdef DEBUG
+      mAcceptingNonWorkerRunnables = true;
+#endif
+      mWorkerPrivate = nullptr;
+    }
+  }
+}
+
+void WorkerThread::IncrementDispatchCounter() {
+  MutexAutoLock lock(mLock);
+  if (mWorkerPrivate) {
+    mWorkerPrivate->MutablePerformanceCounterRef().IncrementDispatchCounter(
+        DispatchCategory::Worker);
+  }
+}
+
+nsresult WorkerThread::DispatchPrimaryRunnable(
+    const WorkerThreadFriendKey& /* aKey */,
+    already_AddRefed<nsIRunnable> aRunnable) {
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+
+#ifdef DEBUG
+  MOZ_ASSERT(PR_GetCurrentThread() != mThread);
+  MOZ_ASSERT(runnable);
+  {
+    MutexAutoLock lock(mLock);
+
+    MOZ_ASSERT(!mWorkerPrivate);
+    MOZ_ASSERT(mAcceptingNonWorkerRunnables);
+  }
+#endif
+
+  nsresult rv = nsThread::Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+nsresult WorkerThread::DispatchAnyThread(
+    const WorkerThreadFriendKey& /* aKey */,
+    already_AddRefed<WorkerRunnable> aWorkerRunnable) {
+  // May be called on any thread!
+
+#ifdef DEBUG
+  {
+    const bool onWorkerThread = PR_GetCurrentThread() == mThread;
+    {
+      MutexAutoLock lock(mLock);
+
+      MOZ_ASSERT(mWorkerPrivate);
+      MOZ_ASSERT(!mAcceptingNonWorkerRunnables);
+
+      if (onWorkerThread) {
+        mWorkerPrivate->AssertIsOnWorkerThread();
+      }
+    }
+  }
+#endif
+
+  // Increment the PerformanceCounter dispatch count
+  // to keep track of how many runnables are executed.
+  IncrementDispatchCounter();
+  nsCOMPtr<nsIRunnable> runnable(aWorkerRunnable);
+
+  nsresult rv = nsThread::Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // We don't need to notify the worker's condition variable here because we're
+  // being called from worker-controlled code and it will make sure to wake up
+  // the worker thread if needed.
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WorkerThread::DispatchFromScript(nsIRunnable* aRunnable, uint32_t aFlags) {
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);
+  return Dispatch(runnable.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+WorkerThread::Dispatch(already_AddRefed<nsIRunnable> aRunnable,
+                       uint32_t aFlags) {
+  // May be called on any thread!
+  nsCOMPtr<nsIRunnable> runnable(aRunnable);  // in case we exit early
+
+  // Workers only support asynchronous dispatch.
+  if (NS_WARN_IF(aFlags != NS_DISPATCH_NORMAL)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  const bool onWorkerThread = PR_GetCurrentThread() == mThread;
+
+#ifdef DEBUG
+  if (runnable && !onWorkerThread) {
+    nsCOMPtr<nsIDiscardableRunnable> discardable = do_QueryInterface(runnable);
+
+    {
+      MutexAutoLock lock(mLock);
+
+      // Only enforce discardable runnables after we've started the worker loop.
+      if (!mAcceptingNonWorkerRunnables) {
+        MOZ_ASSERT(
+            discardable,
+            "Only nsIDiscardableRunnable may be dispatched to a worker!");
+      }
+    }
+  }
+#endif
+
+  WorkerPrivate* workerPrivate = nullptr;
+  if (onWorkerThread) {
+    // No need to lock here because it is only modified on this thread.
+    MOZ_ASSERT(mWorkerPrivate);
+    mWorkerPrivate->AssertIsOnWorkerThread();
+
+    workerPrivate = mWorkerPrivate;
+  } else {
+    MutexAutoLock lock(mLock);
+
+    MOZ_ASSERT(mOtherThreadsDispatchingViaEventTarget < UINT32_MAX);
+
+    if (mWorkerPrivate) {
+      workerPrivate = mWorkerPrivate;
+
+      // Incrementing this counter will make the worker thread sleep if it
+      // somehow tries to unset mWorkerPrivate while we're using it.
+      mOtherThreadsDispatchingViaEventTarget++;
+    }
+  }
+
+  // Increment the PerformanceCounter dispatch count
+  // to keep track of how many runnables are executed.
+  IncrementDispatchCounter();
+  nsresult rv;
+  if (runnable && onWorkerThread) {
+    RefPtr<WorkerRunnable> workerRunnable =
+        workerPrivate->MaybeWrapAsWorkerRunnable(runnable.forget());
+    rv = nsThread::Dispatch(workerRunnable.forget(), NS_DISPATCH_NORMAL);
+  } else {
+    rv = nsThread::Dispatch(runnable.forget(), NS_DISPATCH_NORMAL);
+  }
+
+  if (!onWorkerThread && workerPrivate) {
+    // We need to wake the worker thread if we're not already on the right
+    // thread and the dispatch succeeded.
+    if (NS_SUCCEEDED(rv)) {
+      MutexAutoLock workerLock(workerPrivate->mMutex);
+
+      workerPrivate->mCondVar.Notify();
+    }
+
+    // Now unset our waiting flag.
+    {
+      MutexAutoLock lock(mLock);
+
+      MOZ_ASSERT(mOtherThreadsDispatchingViaEventTarget);
+
+      if (!--mOtherThreadsDispatchingViaEventTarget) {
+        mWorkerPrivateCondVar.Notify();
+      }
+    }
+  }
+
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WorkerThread::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+uint32_t WorkerThread::RecursionDepth(
+    const WorkerThreadFriendKey& /* aKey */) const {
+  MOZ_ASSERT(PR_GetCurrentThread() == mThread);
+
+  return mNestedEventLoopDepth;
+}
+
+PerformanceCounter* WorkerThread::GetPerformanceCounter(nsIRunnable*) const {
+  return mWorkerPrivate ? &mWorkerPrivate->MutablePerformanceCounterRef()
+                        : nullptr;
+}
+
+NS_IMPL_ISUPPORTS(WorkerThread::Observer, nsIThreadObserver)
+
+NS_IMETHODIMP
+WorkerThread::Observer::OnDispatchedEvent() {
+  MOZ_CRASH("OnDispatchedEvent() should never be called!");
+}
+
+NS_IMETHODIMP
+WorkerThread::Observer::OnProcessNextEvent(nsIThreadInternal* /* aThread */,
+                                           bool aMayWait) {
+  mWorkerPrivate->AssertIsOnWorkerThread();
+
+  // If the PBackground child is not created yet, then we must permit
+  // blocking event processing to support
+  // BackgroundChild::GetOrCreateCreateForCurrentThread(). If this occurs
+  // then we are spinning on the event queue at the start of
+  // PrimaryWorkerRunnable::Run() and don't want to process the event in
+  // mWorkerPrivate yet.
+  if (aMayWait) {
+    MOZ_ASSERT(CycleCollectedJSContext::Get()->RecursionDepth() == 2);
+    MOZ_ASSERT(!BackgroundChild::GetForCurrentThread());
+    return NS_OK;
+  }
+
+  mWorkerPrivate->OnProcessNextEvent();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WorkerThread::Observer::AfterProcessNextEvent(nsIThreadInternal* /* aThread */,
+                                              bool /* aEventWasProcessed */) {
+  mWorkerPrivate->AssertIsOnWorkerThread();
+
+  mWorkerPrivate->AfterProcessNextEvent();
+  return NS_OK;
+}
+
+}  // namespace dom
+}  // namespace mozilla