1 files changed, 449 insertions, 0 deletions
diff --git a/xpcom/threads/nsThreadPool.cpp b/xpcom/threads/nsThreadPool.cpp
new file mode 100644
index 0000000000..241fad39dc
--- /dev/null
+++ b/xpcom/threads/nsThreadPool.cpp
@@ -0,0 +1,449 @@
+/* -*- 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 "nsIClassInfoImpl.h"
+#include "nsThreadPool.h"
+#include "nsThreadManager.h"
+#include "nsThread.h"
+#include "nsMemory.h"
+#include "nsAutoPtr.h"
+#include "prinrval.h"
+#include "mozilla/Logging.h"
+#include "nsThreadSyncDispatch.h"
+
+using namespace mozilla;
+
+static LazyLogModule sThreadPoolLog("nsThreadPool");
+#ifdef LOG
+#undef LOG
+#endif
+#define LOG(args) MOZ_LOG(sThreadPoolLog, mozilla::LogLevel::Debug, args)
+
+// DESIGN:
+//  o  Allocate anonymous threads.
+//  o  Use nsThreadPool::Run as the main routine for each thread.
+//  o  Each thread waits on the event queue's monitor, checking for
+//     pending events and rescheduling itself as an idle thread.
+
+#define DEFAULT_THREAD_LIMIT 4
+#define DEFAULT_IDLE_THREAD_LIMIT 1
+#define DEFAULT_IDLE_THREAD_TIMEOUT PR_SecondsToInterval(60)
+
+NS_IMPL_ADDREF(nsThreadPool)
+NS_IMPL_RELEASE(nsThreadPool)
+NS_IMPL_CLASSINFO(nsThreadPool, nullptr, nsIClassInfo::THREADSAFE,
+                  NS_THREADPOOL_CID)
+NS_IMPL_QUERY_INTERFACE_CI(nsThreadPool, nsIThreadPool, nsIEventTarget,
+                           nsIRunnable)
+NS_IMPL_CI_INTERFACE_GETTER(nsThreadPool, nsIThreadPool, nsIEventTarget)
+
+nsThreadPool::nsThreadPool()
+  : mMutex("[nsThreadPool.mMutex]")
+  , mEventsAvailable(mMutex, "[nsThreadPool.mEventsAvailable]")
+  , mEvents(mEventsAvailable, nsEventQueue::eNormalQueue)
+  , mThreadLimit(DEFAULT_THREAD_LIMIT)
+  , mIdleThreadLimit(DEFAULT_IDLE_THREAD_LIMIT)
+  , mIdleThreadTimeout(DEFAULT_IDLE_THREAD_TIMEOUT)
+  , mIdleCount(0)
+  , mStackSize(nsIThreadManager::DEFAULT_STACK_SIZE)
+  , mShutdown(false)
+{
+  LOG(("THRD-P(%p) constructor!!!\n", this));
+}
+
+nsThreadPool::~nsThreadPool()
+{
+  // Threads keep a reference to the nsThreadPool until they return from Run()
+  // after removing themselves from mThreads.
+  MOZ_ASSERT(mThreads.IsEmpty());
+}
+
+nsresult
+nsThreadPool::PutEvent(nsIRunnable* aEvent)
+{
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  return PutEvent(event.forget(), 0);
+}
+
+nsresult
+nsThreadPool::PutEvent(already_AddRefed<nsIRunnable> aEvent, uint32_t aFlags)
+{
+  // Avoid spawning a new thread while holding the event queue lock...
+
+  bool spawnThread = false;
+  uint32_t stackSize = 0;
+  {
+    MutexAutoLock lock(mMutex);
+
+    if (NS_WARN_IF(mShutdown)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+    LOG(("THRD-P(%p) put [%d %d %d]\n", this, mIdleCount, mThreads.Count(),
+         mThreadLimit));
+    MOZ_ASSERT(mIdleCount <= (uint32_t)mThreads.Count(), "oops");
+
+    // Make sure we have a thread to service this event.
+    if (mThreads.Count() < (int32_t)mThreadLimit &&
+        !(aFlags & NS_DISPATCH_AT_END) &&
+        // Spawn a new thread if we don't have enough idle threads to serve
+        // pending events immediately.
+        mEvents.Count(lock) >= mIdleCount) {
+      spawnThread = true;
+    }
+
+    mEvents.PutEvent(Move(aEvent), lock);
+    stackSize = mStackSize;
+  }
+
+  LOG(("THRD-P(%p) put [spawn=%d]\n", this, spawnThread));
+  if (!spawnThread) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIThread> thread;
+  nsThreadManager::get().NewThread(0, stackSize, getter_AddRefs(thread));
+  if (NS_WARN_IF(!thread)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  bool killThread = false;
+  {
+    MutexAutoLock lock(mMutex);
+    if (mThreads.Count() < (int32_t)mThreadLimit) {
+      mThreads.AppendObject(thread);
+    } else {
+      killThread = true;  // okay, we don't need this thread anymore
+    }
+  }
+  LOG(("THRD-P(%p) put [%p kill=%d]\n", this, thread.get(), killThread));
+  if (killThread) {
+    // We never dispatched any events to the thread, so we can shut it down
+    // asynchronously without worrying about anything.
+    ShutdownThread(thread);
+  } else {
+    thread->Dispatch(this, NS_DISPATCH_NORMAL);
+  }
+
+  return NS_OK;
+}
+
+void
+nsThreadPool::ShutdownThread(nsIThread* aThread)
+{
+  LOG(("THRD-P(%p) shutdown async [%p]\n", this, aThread));
+
+  // This is either called by a threadpool thread that is out of work, or
+  // a thread that attempted to create a threadpool thread and raced in
+  // such a way that the newly created thread is no longer necessary.
+  // In the first case, we must go to another thread to shut aThread down
+  // (because it is the current thread).  In the second case, we cannot
+  // synchronously shut down the current thread (because then Dispatch() would
+  // spin the event loop, and that could blow up the world), and asynchronous
+  // shutdown requires this thread have an event loop (and it may not, see bug
+  // 10204784).  The simplest way to cover all cases is to asynchronously
+  // shutdown aThread from the main thread.
+  NS_DispatchToMainThread(NewRunnableMethod(aThread,
+                                            &nsIThread::AsyncShutdown));
+}
+
+NS_IMETHODIMP
+nsThreadPool::Run()
+{
+  mThreadNaming.SetThreadPoolName(mName);
+
+  LOG(("THRD-P(%p) enter %s\n", this, mName.BeginReading()));
+
+  nsCOMPtr<nsIThread> current;
+  nsThreadManager::get().GetCurrentThread(getter_AddRefs(current));
+
+  bool shutdownThreadOnExit = false;
+  bool exitThread = false;
+  bool wasIdle = false;
+  PRIntervalTime idleSince;
+
+  nsCOMPtr<nsIThreadPoolListener> listener;
+  {
+    MutexAutoLock lock(mMutex);
+    listener = mListener;
+  }
+
+  if (listener) {
+    listener->OnThreadCreated();
+  }
+
+  do {
+    nsCOMPtr<nsIRunnable> event;
+    {
+      MutexAutoLock lock(mMutex);
+
+      if (!mEvents.GetPendingEvent(getter_AddRefs(event), lock)) {
+        PRIntervalTime now     = PR_IntervalNow();
+        PRIntervalTime timeout = PR_MillisecondsToInterval(mIdleThreadTimeout);
+
+        // If we are shutting down, then don't keep any idle threads
+        if (mShutdown) {
+          exitThread = true;
+        } else {
+          if (wasIdle) {
+            // if too many idle threads or idle for too long, then bail.
+            if (mIdleCount > mIdleThreadLimit ||
+                (mIdleThreadTimeout != UINT32_MAX && (now - idleSince) >= timeout)) {
+              exitThread = true;
+            }
+          } else {
+            // if would be too many idle threads...
+            if (mIdleCount == mIdleThreadLimit) {
+              exitThread = true;
+            } else {
+              ++mIdleCount;
+              idleSince = now;
+              wasIdle = true;
+            }
+          }
+        }
+
+        if (exitThread) {
+          if (wasIdle) {
+            --mIdleCount;
+          }
+          shutdownThreadOnExit = mThreads.RemoveObject(current);
+        } else {
+          PRIntervalTime delta = timeout - (now - idleSince);
+          LOG(("THRD-P(%p) %s waiting [%d]\n", this, mName.BeginReading(), delta));
+          mEvents.Wait(delta);
+          LOG(("THRD-P(%p) done waiting\n", this));
+        }
+      } else if (wasIdle) {
+        wasIdle = false;
+        --mIdleCount;
+      }
+    }
+    if (event) {
+      LOG(("THRD-P(%p) %s running [%p]\n", this, mName.BeginReading(), event.get()));
+      event->Run();
+    }
+  } while (!exitThread);
+
+  if (listener) {
+    listener->OnThreadShuttingDown();
+  }
+
+  if (shutdownThreadOnExit) {
+    ShutdownThread(current);
+  }
+
+  LOG(("THRD-P(%p) leave\n", this));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::DispatchFromScript(nsIRunnable* aEvent, uint32_t aFlags)
+{
+  nsCOMPtr<nsIRunnable> event(aEvent);
+  return Dispatch(event.forget(), aFlags);
+}
+
+NS_IMETHODIMP
+nsThreadPool::Dispatch(already_AddRefed<nsIRunnable> aEvent, uint32_t aFlags)
+{
+  LOG(("THRD-P(%p) dispatch [%p %x]\n", this, /* XXX aEvent*/ nullptr, aFlags));
+
+  if (NS_WARN_IF(mShutdown)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (aFlags & DISPATCH_SYNC) {
+    nsCOMPtr<nsIThread> thread;
+    nsThreadManager::get().GetCurrentThread(getter_AddRefs(thread));
+    if (NS_WARN_IF(!thread)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+
+    RefPtr<nsThreadSyncDispatch> wrapper =
+      new nsThreadSyncDispatch(thread, Move(aEvent));
+    PutEvent(wrapper);
+
+    while (wrapper->IsPending()) {
+      NS_ProcessNextEvent(thread);
+    }
+  } else {
+    NS_ASSERTION(aFlags == NS_DISPATCH_NORMAL ||
+                 aFlags == NS_DISPATCH_AT_END, "unexpected dispatch flags");
+    PutEvent(Move(aEvent), aFlags);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t)
+{
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsThreadPool::IsOnCurrentThread(bool* aResult)
+{
+  MutexAutoLock lock(mMutex);
+  if (NS_WARN_IF(mShutdown)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsIThread* thread = NS_GetCurrentThread();
+  for (uint32_t i = 0; i < static_cast<uint32_t>(mThreads.Count()); ++i) {
+    if (mThreads[i] == thread) {
+      *aResult = true;
+      return NS_OK;
+    }
+  }
+  *aResult = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::Shutdown()
+{
+  nsCOMArray<nsIThread> threads;
+  nsCOMPtr<nsIThreadPoolListener> listener;
+  {
+    MutexAutoLock lock(mMutex);
+    mShutdown = true;
+    mEvents.NotifyAll();
+
+    threads.AppendObjects(mThreads);
+    mThreads.Clear();
+
+    // Swap in a null listener so that we release the listener at the end of
+    // this method. The listener will be kept alive as long as the other threads
+    // that were created when it was set.
+    mListener.swap(listener);
+  }
+
+  // It's important that we shutdown the threads while outside the event queue
+  // monitor.  Otherwise, we could end up dead-locking.
+
+  for (int32_t i = 0; i < threads.Count(); ++i) {
+    threads[i]->Shutdown();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::GetThreadLimit(uint32_t* aValue)
+{
+  *aValue = mThreadLimit;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::SetThreadLimit(uint32_t aValue)
+{
+  MutexAutoLock lock(mMutex);
+  LOG(("THRD-P(%p) thread limit [%u]\n", this, aValue));
+  mThreadLimit = aValue;
+  if (mIdleThreadLimit > mThreadLimit) {
+    mIdleThreadLimit = mThreadLimit;
+  }
+
+  if (static_cast<uint32_t>(mThreads.Count()) > mThreadLimit) {
+    mEvents.NotifyAll();  // wake up threads so they observe this change
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::GetIdleThreadLimit(uint32_t* aValue)
+{
+  *aValue = mIdleThreadLimit;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::SetIdleThreadLimit(uint32_t aValue)
+{
+  MutexAutoLock lock(mMutex);
+  LOG(("THRD-P(%p) idle thread limit [%u]\n", this, aValue));
+  mIdleThreadLimit = aValue;
+  if (mIdleThreadLimit > mThreadLimit) {
+    mIdleThreadLimit = mThreadLimit;
+  }
+
+  // Do we need to kill some idle threads?
+  if (mIdleCount > mIdleThreadLimit) {
+    mEvents.NotifyAll();  // wake up threads so they observe this change
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::GetIdleThreadTimeout(uint32_t* aValue)
+{
+  *aValue = mIdleThreadTimeout;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::SetIdleThreadTimeout(uint32_t aValue)
+{
+  MutexAutoLock lock(mMutex);
+  uint32_t oldTimeout = mIdleThreadTimeout;
+  mIdleThreadTimeout = aValue;
+
+  // Do we need to notify any idle threads that their sleep time has shortened?
+  if (mIdleThreadTimeout < oldTimeout && mIdleCount > 0) {
+    mEvents.NotifyAll();  // wake up threads so they observe this change
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::GetThreadStackSize(uint32_t* aValue)
+{
+  MutexAutoLock lock(mMutex);
+  *aValue = mStackSize;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::SetThreadStackSize(uint32_t aValue)
+{
+  MutexAutoLock lock(mMutex);
+  mStackSize = aValue;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::GetListener(nsIThreadPoolListener** aListener)
+{
+  MutexAutoLock lock(mMutex);
+  NS_IF_ADDREF(*aListener = mListener);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::SetListener(nsIThreadPoolListener* aListener)
+{
+  nsCOMPtr<nsIThreadPoolListener> swappedListener(aListener);
+  {
+    MutexAutoLock lock(mMutex);
+    mListener.swap(swappedListener);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsThreadPool::SetName(const nsACString& aName)
+{
+  {
+    MutexAutoLock lock(mMutex);
+    if (mThreads.Count()) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  mName = aName;
+  return NS_OK;
+}