Add m-esr52 at 52.6.0

1 files changed, 752 insertions, 0 deletions

diff --git a/xpcom/threads/TimerThread.cpp b/xpcom/threads/TimerThread.cpp
new file mode 100644
index 000000000..0127e2dd1
--- /dev/null
+++ b/xpcom/threads/TimerThread.cpp
@@ -0,0 +1,752 @@
+/* -*- 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 "nsTimerImpl.h"
+#include "TimerThread.h"
+
+#include "nsThreadUtils.h"
+#include "plarena.h"
+#include "pratom.h"
+
+#include "nsIObserverService.h"
+#include "nsIServiceManager.h"
+#include "mozilla/Services.h"
+#include "mozilla/ChaosMode.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/BinarySearch.h"
+
+#include <math.h>
+
+using namespace mozilla;
+#ifdef MOZ_TASK_TRACER
+#include "GeckoTaskTracerImpl.h"
+using namespace mozilla::tasktracer;
+#endif
+
+NS_IMPL_ISUPPORTS(TimerThread, nsIRunnable, nsIObserver)
+
+TimerThread::TimerThread() :
+  mInitInProgress(false),
+  mInitialized(false),
+  mMonitor("TimerThread.mMonitor"),
+  mShutdown(false),
+  mWaiting(false),
+  mNotified(false),
+  mSleeping(false)
+{
+}
+
+TimerThread::~TimerThread()
+{
+  mThread = nullptr;
+
+  NS_ASSERTION(mTimers.IsEmpty(), "Timers remain in TimerThread::~TimerThread");
+}
+
+nsresult
+TimerThread::InitLocks()
+{
+  return NS_OK;
+}
+
+namespace {
+
+class TimerObserverRunnable : public Runnable
+{
+public:
+  explicit TimerObserverRunnable(nsIObserver* aObserver)
+    : mObserver(aObserver)
+  {
+  }
+
+  NS_DECL_NSIRUNNABLE
+
+private:
+  nsCOMPtr<nsIObserver> mObserver;
+};
+
+NS_IMETHODIMP
+TimerObserverRunnable::Run()
+{
+  nsCOMPtr<nsIObserverService> observerService =
+    mozilla::services::GetObserverService();
+  if (observerService) {
+    observerService->AddObserver(mObserver, "sleep_notification", false);
+    observerService->AddObserver(mObserver, "wake_notification", false);
+    observerService->AddObserver(mObserver, "suspend_process_notification", false);
+    observerService->AddObserver(mObserver, "resume_process_notification", false);
+  }
+  return NS_OK;
+}
+
+} // namespace
+
+namespace {
+
+// TimerEventAllocator is a thread-safe allocator used only for nsTimerEvents.
+// It's needed to avoid contention over the default allocator lock when
+// firing timer events (see bug 733277).  The thread-safety is required because
+// nsTimerEvent objects are allocated on the timer thread, and freed on another
+// thread.  Because TimerEventAllocator has its own lock, contention over that
+// lock is limited to the allocation and deallocation of nsTimerEvent objects.
+//
+// Because this allocator is layered over PLArenaPool, it never shrinks -- even
+// "freed" nsTimerEvents aren't truly freed, they're just put onto a free-list
+// for later recycling.  So the amount of memory consumed will always be equal
+// to the high-water mark consumption.  But nsTimerEvents are small and it's
+// unusual to have more than a few hundred of them, so this shouldn't be a
+// problem in practice.
+
+class TimerEventAllocator
+{
+private:
+  struct FreeEntry
+  {
+    FreeEntry* mNext;
+  };
+
+  PLArenaPool mPool;
+  FreeEntry* mFirstFree;
+  mozilla::Monitor mMonitor;
+
+public:
+  TimerEventAllocator()
+    : mFirstFree(nullptr)
+    , mMonitor("TimerEventAllocator")
+  {
+    PL_InitArenaPool(&mPool, "TimerEventPool", 4096, /* align = */ 0);
+  }
+
+  ~TimerEventAllocator()
+  {
+    PL_FinishArenaPool(&mPool);
+  }
+
+  void* Alloc(size_t aSize);
+  void Free(void* aPtr);
+};
+
+} // namespace
+
+// This is a nsICancelableRunnable because we can dispatch it to Workers and
+// those can be shut down at any time, and in these cases, Cancel() is called
+// instead of Run().
+class nsTimerEvent final : public CancelableRunnable
+{
+public:
+  NS_IMETHOD Run() override;
+
+  nsresult Cancel() override
+  {
+    // Since nsTimerImpl is not thread-safe, we should release |mTimer|
+    // here in the target thread to avoid race condition. Otherwise,
+    // ~nsTimerEvent() which calls nsTimerImpl::Release() could run in the
+    // timer thread and result in race condition.
+    mTimer = nullptr;
+    return NS_OK;
+  }
+
+  nsTimerEvent()
+    : mTimer()
+    , mGeneration(0)
+  {
+    // Note: We override operator new for this class, and the override is
+    // fallible!
+    sAllocatorUsers++;
+  }
+
+  TimeStamp mInitTime;
+
+  static void Init();
+  static void Shutdown();
+  static void DeleteAllocatorIfNeeded();
+
+  static void* operator new(size_t aSize) CPP_THROW_NEW
+  {
+    return sAllocator->Alloc(aSize);
+  }
+  void operator delete(void* aPtr)
+  {
+    sAllocator->Free(aPtr);
+    DeleteAllocatorIfNeeded();
+  }
+
+  already_AddRefed<nsTimerImpl> ForgetTimer()
+  {
+    return mTimer.forget();
+  }
+
+  void SetTimer(already_AddRefed<nsTimerImpl> aTimer)
+  {
+    mTimer = aTimer;
+    mGeneration = mTimer->GetGeneration();
+  }
+
+private:
+  nsTimerEvent(const nsTimerEvent&) = delete;
+  nsTimerEvent& operator=(const nsTimerEvent&) = delete;
+  nsTimerEvent& operator=(const nsTimerEvent&&) = delete;
+
+  ~nsTimerEvent()
+  {
+    MOZ_ASSERT(!sCanDeleteAllocator || sAllocatorUsers > 0,
+               "This will result in us attempting to deallocate the nsTimerEvent allocator twice");
+    sAllocatorUsers--;
+  }
+
+  RefPtr<nsTimerImpl> mTimer;
+  int32_t      mGeneration;
+
+  static TimerEventAllocator* sAllocator;
+  static Atomic<int32_t> sAllocatorUsers;
+  static bool sCanDeleteAllocator;
+};
+
+TimerEventAllocator* nsTimerEvent::sAllocator = nullptr;
+Atomic<int32_t> nsTimerEvent::sAllocatorUsers;
+bool nsTimerEvent::sCanDeleteAllocator = false;
+
+namespace {
+
+void*
+TimerEventAllocator::Alloc(size_t aSize)
+{
+  MOZ_ASSERT(aSize == sizeof(nsTimerEvent));
+
+  mozilla::MonitorAutoLock lock(mMonitor);
+
+  void* p;
+  if (mFirstFree) {
+    p = mFirstFree;
+    mFirstFree = mFirstFree->mNext;
+  } else {
+    PL_ARENA_ALLOCATE(p, &mPool, aSize);
+    if (!p) {
+      return nullptr;
+    }
+  }
+
+  return p;
+}
+
+void
+TimerEventAllocator::Free(void* aPtr)
+{
+  mozilla::MonitorAutoLock lock(mMonitor);
+
+  FreeEntry* entry = reinterpret_cast<FreeEntry*>(aPtr);
+
+  entry->mNext = mFirstFree;
+  mFirstFree = entry;
+}
+
+} // namespace
+
+void
+nsTimerEvent::Init()
+{
+  sAllocator = new TimerEventAllocator();
+}
+
+void
+nsTimerEvent::Shutdown()
+{
+  sCanDeleteAllocator = true;
+  DeleteAllocatorIfNeeded();
+}
+
+void
+nsTimerEvent::DeleteAllocatorIfNeeded()
+{
+  if (sCanDeleteAllocator && sAllocatorUsers == 0) {
+    delete sAllocator;
+    sAllocator = nullptr;
+  }
+}
+
+NS_IMETHODIMP
+nsTimerEvent::Run()
+{
+  if (!mTimer) {
+    MOZ_ASSERT(false);
+    return NS_OK;
+  }
+
+  if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug)) {
+    TimeStamp now = TimeStamp::Now();
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+           ("[this=%p] time between PostTimerEvent() and Fire(): %fms\n",
+            this, (now - mInitTime).ToMilliseconds()));
+  }
+
+  mTimer->Fire(mGeneration);
+
+  // We call Cancel() to correctly release mTimer.
+  // Read more in the Cancel() implementation.
+  return Cancel();
+}
+
+nsresult
+TimerThread::Init()
+{
+  MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+         ("TimerThread::Init [%d]\n", mInitialized));
+
+  if (mInitialized) {
+    if (!mThread) {
+      return NS_ERROR_FAILURE;
+    }
+
+    return NS_OK;
+  }
+
+  nsTimerEvent::Init();
+
+  if (mInitInProgress.exchange(true) == false) {
+    // We hold on to mThread to keep the thread alive.
+    nsresult rv = NS_NewThread(getter_AddRefs(mThread), this);
+    if (NS_FAILED(rv)) {
+      mThread = nullptr;
+    } else {
+      RefPtr<TimerObserverRunnable> r = new TimerObserverRunnable(this);
+      if (NS_IsMainThread()) {
+        r->Run();
+      } else {
+        NS_DispatchToMainThread(r);
+      }
+    }
+
+    {
+      MonitorAutoLock lock(mMonitor);
+      mInitialized = true;
+      mMonitor.NotifyAll();
+    }
+  } else {
+    MonitorAutoLock lock(mMonitor);
+    while (!mInitialized) {
+      mMonitor.Wait();
+    }
+  }
+
+  if (!mThread) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+nsresult
+TimerThread::Shutdown()
+{
+  MOZ_LOG(GetTimerLog(), LogLevel::Debug, ("TimerThread::Shutdown begin\n"));
+
+  if (!mThread) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  nsTArray<nsTimerImpl*> timers;
+  {
+    // lock scope
+    MonitorAutoLock lock(mMonitor);
+
+    mShutdown = true;
+
+    // notify the cond var so that Run() can return
+    if (mWaiting) {
+      mNotified = true;
+      mMonitor.Notify();
+    }
+
+    // Need to copy content of mTimers array to a local array
+    // because call to timers' Cancel() (and release its self)
+    // must not be done under the lock. Destructor of a callback
+    // might potentially call some code reentering the same lock
+    // that leads to unexpected behavior or deadlock.
+    // See bug 422472.
+    timers.AppendElements(mTimers);
+    mTimers.Clear();
+  }
+
+  uint32_t timersCount = timers.Length();
+  for (uint32_t i = 0; i < timersCount; i++) {
+    nsTimerImpl* timer = timers[i];
+    timer->Cancel();
+    ReleaseTimerInternal(timer);
+  }
+
+  mThread->Shutdown();    // wait for the thread to die
+
+  nsTimerEvent::Shutdown();
+
+  MOZ_LOG(GetTimerLog(), LogLevel::Debug, ("TimerThread::Shutdown end\n"));
+  return NS_OK;
+}
+
+namespace {
+
+struct MicrosecondsToInterval
+{
+  PRIntervalTime operator[](size_t aMs) const {
+    return PR_MicrosecondsToInterval(aMs);
+  }
+};
+
+struct IntervalComparator
+{
+  int operator()(PRIntervalTime aInterval) const {
+    return (0 < aInterval) ? -1 : 1;
+  }
+};
+
+} // namespace
+
+NS_IMETHODIMP
+TimerThread::Run()
+{
+  PR_SetCurrentThreadName("Timer");
+
+  MonitorAutoLock lock(mMonitor);
+
+  // We need to know how many microseconds give a positive PRIntervalTime. This
+  // is platform-dependent and we calculate it at runtime, finding a value |v|
+  // such that |PR_MicrosecondsToInterval(v) > 0| and then binary-searching in
+  // the range [0, v) to find the ms-to-interval scale.
+  uint32_t usForPosInterval = 1;
+  while (PR_MicrosecondsToInterval(usForPosInterval) == 0) {
+    usForPosInterval <<= 1;
+  }
+
+  size_t usIntervalResolution;
+  BinarySearchIf(MicrosecondsToInterval(), 0, usForPosInterval, IntervalComparator(), &usIntervalResolution);
+  MOZ_ASSERT(PR_MicrosecondsToInterval(usIntervalResolution - 1) == 0);
+  MOZ_ASSERT(PR_MicrosecondsToInterval(usIntervalResolution) == 1);
+
+  // Half of the amount of microseconds needed to get positive PRIntervalTime.
+  // We use this to decide how to round our wait times later
+  int32_t halfMicrosecondsIntervalResolution = usIntervalResolution / 2;
+  bool forceRunNextTimer = false;
+
+  while (!mShutdown) {
+    // Have to use PRIntervalTime here, since PR_WaitCondVar takes it
+    PRIntervalTime waitFor;
+    bool forceRunThisTimer = forceRunNextTimer;
+    forceRunNextTimer = false;
+
+    if (mSleeping) {
+      // Sleep for 0.1 seconds while not firing timers.
+      uint32_t milliseconds = 100;
+      if (ChaosMode::isActive(ChaosFeature::TimerScheduling)) {
+        milliseconds = ChaosMode::randomUint32LessThan(200);
+      }
+      waitFor = PR_MillisecondsToInterval(milliseconds);
+    } else {
+      waitFor = PR_INTERVAL_NO_TIMEOUT;
+      TimeStamp now = TimeStamp::Now();
+      nsTimerImpl* timer = nullptr;
+
+      if (!mTimers.IsEmpty()) {
+        timer = mTimers[0];
+
+        if (now >= timer->mTimeout || forceRunThisTimer) {
+    next:
+          // NB: AddRef before the Release under RemoveTimerInternal to avoid
+          // mRefCnt passing through zero, in case all other refs than the one
+          // from mTimers have gone away (the last non-mTimers[i]-ref's Release
+          // must be racing with us, blocked in gThread->RemoveTimer waiting
+          // for TimerThread::mMonitor, under nsTimerImpl::Release.
+
+          RefPtr<nsTimerImpl> timerRef(timer);
+          RemoveTimerInternal(timer);
+          timer = nullptr;
+
+          MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+                 ("Timer thread woke up %fms from when it was supposed to\n",
+                  fabs((now - timerRef->mTimeout).ToMilliseconds())));
+
+          // We are going to let the call to PostTimerEvent here handle the
+          // release of the timer so that we don't end up releasing the timer
+          // on the TimerThread instead of on the thread it targets.
+          timerRef = PostTimerEvent(timerRef.forget());
+
+          if (timerRef) {
+            // We got our reference back due to an error.
+            // Unhook the nsRefPtr, and release manually so we can get the
+            // refcount.
+            nsrefcnt rc = timerRef.forget().take()->Release();
+            (void)rc;
+
+            // The nsITimer interface requires that its users keep a reference
+            // to the timers they use while those timers are initialized but
+            // have not yet fired.  If this ever happens, it is a bug in the
+            // code that created and used the timer.
+            //
+            // Further, note that this should never happen even with a
+            // misbehaving user, because nsTimerImpl::Release checks for a
+            // refcount of 1 with an armed timer (a timer whose only reference
+            // is from the timer thread) and when it hits this will remove the
+            // timer from the timer thread and thus destroy the last reference,
+            // preventing this situation from occurring.
+            MOZ_ASSERT(rc != 0, "destroyed timer off its target thread!");
+          }
+
+          if (mShutdown) {
+            break;
+          }
+
+          // Update now, as PostTimerEvent plus the locking may have taken a
+          // tick or two, and we may goto next below.
+          now = TimeStamp::Now();
+        }
+      }
+
+      if (!mTimers.IsEmpty()) {
+        timer = mTimers[0];
+
+        TimeStamp timeout = timer->mTimeout;
+
+        // Don't wait at all (even for PR_INTERVAL_NO_WAIT) if the next timer
+        // is due now or overdue.
+        //
+        // Note that we can only sleep for integer values of a certain
+        // resolution. We use halfMicrosecondsIntervalResolution, calculated
+        // before, to do the optimal rounding (i.e., of how to decide what
+        // interval is so small we should not wait at all).
+        double microseconds = (timeout - now).ToMilliseconds() * 1000;
+
+        if (ChaosMode::isActive(ChaosFeature::TimerScheduling)) {
+          // The mean value of sFractions must be 1 to ensure that
+          // the average of a long sequence of timeouts converges to the
+          // actual sum of their times.
+          static const float sFractions[] = {
+            0.0f, 0.25f, 0.5f, 0.75f, 1.0f, 1.75f, 2.75f
+          };
+          microseconds *=
+            sFractions[ChaosMode::randomUint32LessThan(ArrayLength(sFractions))];
+          forceRunNextTimer = true;
+        }
+
+        if (microseconds < halfMicrosecondsIntervalResolution) {
+          forceRunNextTimer = false;
+          goto next; // round down; execute event now
+        }
+        waitFor = PR_MicrosecondsToInterval(
+          static_cast<uint32_t>(microseconds)); // Floor is accurate enough.
+        if (waitFor == 0) {
+          waitFor = 1;  // round up, wait the minimum time we can wait
+        }
+      }
+
+      if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug)) {
+        if (waitFor == PR_INTERVAL_NO_TIMEOUT)
+          MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+                 ("waiting for PR_INTERVAL_NO_TIMEOUT\n"));
+        else
+          MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+                 ("waiting for %u\n", PR_IntervalToMilliseconds(waitFor)));
+      }
+    }
+
+    mWaiting = true;
+    mNotified = false;
+    mMonitor.Wait(waitFor);
+    if (mNotified) {
+      forceRunNextTimer = false;
+    }
+    mWaiting = false;
+  }
+
+  return NS_OK;
+}
+
+nsresult
+TimerThread::AddTimer(nsTimerImpl* aTimer)
+{
+  MonitorAutoLock lock(mMonitor);
+
+  if (!aTimer->mEventTarget) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  // Add the timer to our list.
+  int32_t i = AddTimerInternal(aTimer);
+  if (i < 0) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  // Awaken the timer thread.
+  if (mWaiting && i == 0) {
+    mNotified = true;
+    mMonitor.Notify();
+  }
+
+  return NS_OK;
+}
+
+nsresult
+TimerThread::RemoveTimer(nsTimerImpl* aTimer)
+{
+  MonitorAutoLock lock(mMonitor);
+
+  // Remove the timer from our array.  Tell callers that aTimer was not found
+  // by returning NS_ERROR_NOT_AVAILABLE.
+
+  if (!RemoveTimerInternal(aTimer)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // Awaken the timer thread.
+  if (mWaiting) {
+    mNotified = true;
+    mMonitor.Notify();
+  }
+
+  return NS_OK;
+}
+
+// This function must be called from within a lock
+int32_t
+TimerThread::AddTimerInternal(nsTimerImpl* aTimer)
+{
+  mMonitor.AssertCurrentThreadOwns();
+  if (mShutdown) {
+    return -1;
+  }
+
+  TimeStamp now = TimeStamp::Now();
+
+  TimerAdditionComparator c(now, aTimer);
+  nsTimerImpl** insertSlot = mTimers.InsertElementSorted(aTimer, c);
+
+  if (!insertSlot) {
+    return -1;
+  }
+
+  NS_ADDREF(aTimer);
+
+#ifdef MOZ_TASK_TRACER
+  // Caller of AddTimer is the parent task of its timer event, so we store the
+  // TraceInfo here for later used.
+  aTimer->GetTLSTraceInfo();
+#endif
+
+  return insertSlot - mTimers.Elements();
+}
+
+bool
+TimerThread::RemoveTimerInternal(nsTimerImpl* aTimer)
+{
+  mMonitor.AssertCurrentThreadOwns();
+  if (!mTimers.RemoveElement(aTimer)) {
+    return false;
+  }
+
+  ReleaseTimerInternal(aTimer);
+  return true;
+}
+
+void
+TimerThread::ReleaseTimerInternal(nsTimerImpl* aTimer)
+{
+  if (!mShutdown) {
+    // copied to a local array before releasing in shutdown
+    mMonitor.AssertCurrentThreadOwns();
+  }
+  NS_RELEASE(aTimer);
+}
+
+already_AddRefed<nsTimerImpl>
+TimerThread::PostTimerEvent(already_AddRefed<nsTimerImpl> aTimerRef)
+{
+  mMonitor.AssertCurrentThreadOwns();
+
+  RefPtr<nsTimerImpl> timer(aTimerRef);
+  if (!timer->mEventTarget) {
+    NS_ERROR("Attempt to post timer event to NULL event target");
+    return timer.forget();
+  }
+
+  // XXX we may want to reuse this nsTimerEvent in the case of repeating timers.
+
+  // Since we already addref'd 'timer', we don't need to addref here.
+  // We will release either in ~nsTimerEvent(), or pass the reference back to
+  // the caller. We need to copy the generation number from this timer into the
+  // event, so we can avoid firing a timer that was re-initialized after being
+  // canceled.
+
+  RefPtr<nsTimerEvent> event = new nsTimerEvent;
+  if (!event) {
+    return timer.forget();
+  }
+
+  if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug)) {
+    event->mInitTime = TimeStamp::Now();
+  }
+
+#ifdef MOZ_TASK_TRACER
+  // During the dispatch of TimerEvent, we overwrite the current TraceInfo
+  // partially with the info saved in timer earlier, and restore it back by
+  // AutoSaveCurTraceInfo.
+  AutoSaveCurTraceInfo saveCurTraceInfo;
+  (timer->GetTracedTask()).SetTLSTraceInfo();
+#endif
+
+  nsCOMPtr<nsIEventTarget> target = timer->mEventTarget;
+  event->SetTimer(timer.forget());
+
+  nsresult rv;
+  {
+    // We release mMonitor around the Dispatch because if this timer is targeted
+    // at the TimerThread we'll deadlock.
+    MonitorAutoUnlock unlock(mMonitor);
+    rv = target->Dispatch(event, NS_DISPATCH_NORMAL);
+  }
+
+  if (NS_FAILED(rv)) {
+    timer = event->ForgetTimer();
+    RemoveTimerInternal(timer);
+    return timer.forget();
+  }
+
+  return nullptr;
+}
+
+void
+TimerThread::DoBeforeSleep()
+{
+  // Mainthread
+  MonitorAutoLock lock(mMonitor);
+  mSleeping = true;
+}
+
+// Note: wake may be notified without preceding sleep notification
+void
+TimerThread::DoAfterSleep()
+{
+  // Mainthread
+  MonitorAutoLock lock(mMonitor);
+  mSleeping = false;
+
+  // Wake up the timer thread to re-process the array to ensure the sleep delay is correct,
+  // and fire any expired timers (perhaps quite a few)
+  mNotified = true;
+  mMonitor.Notify();
+}
+
+
+NS_IMETHODIMP
+TimerThread::Observe(nsISupports* /* aSubject */, const char* aTopic,
+                     const char16_t* /* aData */)
+{
+  if (strcmp(aTopic, "sleep_notification") == 0 ||
+      strcmp(aTopic, "suspend_process_notification") == 0) {
+    DoBeforeSleep();
+  } else if (strcmp(aTopic, "wake_notification") == 0 ||
+             strcmp(aTopic, "resume_process_notification") == 0) {
+    DoAfterSleep();
+  }
+
+  return NS_OK;
+}