1 files changed, 126 insertions, 0 deletions
diff --git a/xpcom/threads/LazyIdleThread.cpp b/xpcom/threads/LazyIdleThread.cpp
new file mode 100644
index 0000000000..4187fcc4ff
--- /dev/null
+++ b/xpcom/threads/LazyIdleThread.cpp
@@ -0,0 +1,126 @@
+/* -*- 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 "LazyIdleThread.h"
+
+#include "nsIObserverService.h"
+#include "nsServiceManagerUtils.h"
+#include "nsThreadUtils.h"
+
+#ifdef DEBUG
+#  define ASSERT_OWNING_THREAD()                           \
+    do {                                                   \
+      MOZ_ASSERT(mOwningEventTarget->IsOnCurrentThread()); \
+    } while (0)
+#else
+#  define ASSERT_OWNING_THREAD() /* nothing */
+#endif
+
+namespace mozilla {
+
+LazyIdleThread::LazyIdleThread(uint32_t aIdleTimeoutMS, const char* aName,
+                               ShutdownMethod aShutdownMethod)
+    : mOwningEventTarget(GetCurrentSerialEventTarget()),
+      mThreadPool(new nsThreadPool()),
+      mTaskQueue(TaskQueue::Create(do_AddRef(mThreadPool), aName)) {
+  // Configure the threadpool to host a single thread. It will be responsible
+  // for managing the thread's lifetime.
+  MOZ_ALWAYS_SUCCEEDS(mThreadPool->SetThreadLimit(1));
+  MOZ_ALWAYS_SUCCEEDS(mThreadPool->SetIdleThreadLimit(1));
+  MOZ_ALWAYS_SUCCEEDS(mThreadPool->SetIdleThreadTimeout(aIdleTimeoutMS));
+  MOZ_ALWAYS_SUCCEEDS(mThreadPool->SetName(nsDependentCString(aName)));
+
+  if (aShutdownMethod == ShutdownMethod::AutomaticShutdown &&
+      NS_IsMainThread()) {
+    if (nsCOMPtr<nsIObserverService> obs =
+            do_GetService(NS_OBSERVERSERVICE_CONTRACTID)) {
+      MOZ_ALWAYS_SUCCEEDS(
+          obs->AddObserver(this, "xpcom-shutdown-threads", false));
+    }
+  }
+}
+
+static void LazyIdleThreadShutdown(nsThreadPool* aThreadPool,
+                                   TaskQueue* aTaskQueue) {
+  aTaskQueue->BeginShutdown();
+  aTaskQueue->AwaitShutdownAndIdle();
+  aThreadPool->Shutdown();
+}
+
+LazyIdleThread::~LazyIdleThread() {
+  if (!mShutdown) {
+    mOwningEventTarget->Dispatch(NS_NewRunnableFunction(
+        "LazyIdleThread::~LazyIdleThread",
+        [threadPool = mThreadPool, taskQueue = mTaskQueue] {
+          LazyIdleThreadShutdown(threadPool, taskQueue);
+        }));
+  }
+}
+
+void LazyIdleThread::Shutdown() {
+  ASSERT_OWNING_THREAD();
+
+  if (!mShutdown) {
+    mShutdown = true;
+    LazyIdleThreadShutdown(mThreadPool, mTaskQueue);
+  }
+}
+
+nsresult LazyIdleThread::SetListener(nsIThreadPoolListener* aListener) {
+  return mThreadPool->SetListener(aListener);
+}
+
+NS_IMPL_ISUPPORTS(LazyIdleThread, nsIEventTarget, nsISerialEventTarget,
+                  nsIObserver)
+
+NS_IMETHODIMP
+LazyIdleThread::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags) {
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  return Dispatch(event.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+LazyIdleThread::Dispatch(already_AddRefed<nsIRunnable> aEvent,
+                         uint32_t aFlags) {
+  return mTaskQueue->Dispatch(std::move(aEvent), aFlags);
+}
+
+NS_IMETHODIMP
+LazyIdleThread::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+LazyIdleThread::RegisterShutdownTask(nsITargetShutdownTask* aTask) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+LazyIdleThread::UnregisterShutdownTask(nsITargetShutdownTask* aTask) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+LazyIdleThread::IsOnCurrentThread(bool* aIsOnCurrentThread) {
+  return mTaskQueue->IsOnCurrentThread(aIsOnCurrentThread);
+}
+
+NS_IMETHODIMP_(bool)
+LazyIdleThread::IsOnCurrentThreadInfallible() {
+  return mTaskQueue->IsOnCurrentThreadInfallible();
+}
+
+NS_IMETHODIMP
+LazyIdleThread::Observe(nsISupports* /* aSubject */, const char* aTopic,
+                        const char16_t* /* aData */) {
+  MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
+  MOZ_ASSERT(!strcmp("xpcom-shutdown-threads", aTopic), "Bad topic!");
+
+  Shutdown();
+  return NS_OK;
+}
+
+}  // namespace mozilla