xpcom/tests/gtest/TestTimers.cpp
author Carsten "Tomcat" Book <cbook@mozilla.com>
Tue, 20 Jun 2017 08:27:02 +0200
changeset 364872 e61d71c2a3a32013f097777dfa68a9320d4ae61b
parent 364866 9846de3bd9545fb2c2b803a36af85568ccf2473b
child 365276 4f6302a98ae41ff2d57c768996d1edbb0afda73a
permissions -rw-r--r--
Backed out changeset 9846de3bd954 (bug 1372405)

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* 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 "nsIThread.h"
#include "nsITimer.h"

#include "nsCOMPtr.h"
#include "nsComponentManagerUtils.h"
#include "nsServiceManagerUtils.h"
#include "nsThreadUtils.h"
#include "prinrval.h"
#include "prmon.h"
#include "prthread.h"
#include "mozilla/Attributes.h"

#include "mozilla/ReentrantMonitor.h"

#include <list>
#include <vector>

#include "gtest/gtest.h"

using namespace mozilla;

typedef nsresult(*TestFuncPtr)();

class AutoTestThread
{
public:
  AutoTestThread() {
    nsCOMPtr<nsIThread> newThread;
    nsresult rv = NS_NewNamedThread("AutoTestThread", getter_AddRefs(newThread));
    if (NS_FAILED(rv))
      return;

    newThread.swap(mThread);
  }

  ~AutoTestThread() {
    mThread->Shutdown();
  }

  operator nsIThread*() const {
    return mThread;
  }

  nsIThread* operator->() const MOZ_NO_ADDREF_RELEASE_ON_RETURN {
    return mThread;
  }

private:
  nsCOMPtr<nsIThread> mThread;
};

class AutoCreateAndDestroyReentrantMonitor
{
public:
  AutoCreateAndDestroyReentrantMonitor() {
    mReentrantMonitor = new ReentrantMonitor("TestTimers::AutoMon");
    MOZ_RELEASE_ASSERT(mReentrantMonitor, "Out of memory!");
  }

  ~AutoCreateAndDestroyReentrantMonitor() {
    delete mReentrantMonitor;
  }

  operator ReentrantMonitor* () const {
    return mReentrantMonitor;
  }

private:
  ReentrantMonitor* mReentrantMonitor;
};

class TimerCallback final : public nsITimerCallback
{
public:
  NS_DECL_THREADSAFE_ISUPPORTS

  TimerCallback(nsIThread** aThreadPtr, ReentrantMonitor* aReentrantMonitor)
  : mThreadPtr(aThreadPtr), mReentrantMonitor(aReentrantMonitor) { }

  NS_IMETHOD Notify(nsITimer* aTimer) override {
    MOZ_RELEASE_ASSERT(mThreadPtr, "Callback was not supposed to be called!");
    nsCOMPtr<nsIThread> current(do_GetCurrentThread());

    ReentrantMonitorAutoEnter mon(*mReentrantMonitor);

    MOZ_RELEASE_ASSERT(!*mThreadPtr, "Timer called back more than once!");
    *mThreadPtr = current;

    mon.Notify();

    return NS_OK;
  }
private:
  ~TimerCallback() {}

  nsIThread** mThreadPtr;
  ReentrantMonitor* mReentrantMonitor;
};

NS_IMPL_ISUPPORTS(TimerCallback, nsITimerCallback)

TEST(Timers, TargetedTimers)
{
  AutoCreateAndDestroyReentrantMonitor newMon;
  ASSERT_TRUE(newMon);

  AutoTestThread testThread;
  ASSERT_TRUE(testThread);

  nsresult rv;
  nsCOMPtr<nsITimer> timer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
  ASSERT_TRUE(NS_SUCCEEDED(rv));

  nsIEventTarget* target = static_cast<nsIEventTarget*>(testThread);

  rv = timer->SetTarget(target);
  ASSERT_TRUE(NS_SUCCEEDED(rv));

  nsIThread* notifiedThread = nullptr;

  nsCOMPtr<nsITimerCallback> callback =
    new TimerCallback(&notifiedThread, newMon);
  ASSERT_TRUE(callback);

  rv = timer->InitWithCallback(callback, 2000, nsITimer::TYPE_ONE_SHOT);
  ASSERT_TRUE(NS_SUCCEEDED(rv));

  ReentrantMonitorAutoEnter mon(*newMon);
  while (!notifiedThread) {
    mon.Wait();
  }
  ASSERT_EQ(notifiedThread, testThread);
}

TEST(Timers, TimerWithStoppedTarget)
{
  AutoTestThread testThread;
  ASSERT_TRUE(testThread);

  nsresult rv;
  nsCOMPtr<nsITimer> timer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
  ASSERT_TRUE(NS_SUCCEEDED(rv));

  nsIEventTarget* target = static_cast<nsIEventTarget*>(testThread);

  rv = timer->SetTarget(target);
  ASSERT_TRUE(NS_SUCCEEDED(rv));

  // If this is called, we'll assert
  nsCOMPtr<nsITimerCallback> callback =
    new TimerCallback(nullptr, nullptr);
  ASSERT_TRUE(callback);

  rv = timer->InitWithCallback(callback, 100, nsITimer::TYPE_ONE_SHOT);
  ASSERT_TRUE(NS_SUCCEEDED(rv));

  testThread->Shutdown();

  PR_Sleep(400);
}

// gtest on 32bit Win7 debug build is unstable and somehow this test
// makes it even worse.
#if !defined(XP_WIN) || !defined(DEBUG) || defined(HAVE_64BIT_BUILD)

class FindExpirationTimeState final
{
public:
  // We'll offset the timers 10 seconds into the future to assure that they won't fire
  const uint32_t kTimerOffset = 10 * 1000;
  // And we'll set the timers spaced by 5 seconds.
  const uint32_t kTimerInterval = 5 * 1000;
  // We'll use 20 timers
  const uint32_t kNumTimers = 20;

  TimeStamp mBefore;
  TimeStamp mMiddle;

  std::list<nsCOMPtr<nsITimer>> mTimers;

  ~FindExpirationTimeState()
  {
    while (!mTimers.empty()) {
      nsCOMPtr<nsITimer> t = mTimers.front().get();
      mTimers.pop_front();
      t->Cancel();
    }
  }

  // Create timers, with aNumLowPriority low priority timers first in the queue
  void InitTimers(uint32_t aNumLowPriority, uint32_t aType)
  {
    // aType is just for readability.
    MOZ_ASSERT(aType == nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY);
    InitTimers(aNumLowPriority, nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY, nullptr);
  }

  // Create timers, with aNumDifferentTarget timers with target aTarget first in the queue
  void InitTimers(uint32_t aNumDifferentTarget, nsIEventTarget* aTarget)
  {
    InitTimers(aNumDifferentTarget, nsITimer::TYPE_ONE_SHOT, aTarget);
  }

  void InitTimers(uint32_t aNumDifferingTimers, uint32_t aType, nsIEventTarget* aTarget)
  {
    do {
      TimeStamp clearUntil =
        TimeStamp::Now() +
        TimeDuration::FromMilliseconds(kTimerOffset +
                                       kNumTimers * kTimerInterval);

      // NS_GetTimerDeadlineHintOnCurrentThread returns clearUntil if there are
      // no pending timers before clearUntil.
      TimeStamp t = NS_GetTimerDeadlineHintOnCurrentThread(clearUntil, 100);
      if (t >= clearUntil) {
        break;
      }

      // Clear whatever random timers there might be pending.
      uint32_t waitTime = 10;
      if (t > TimeStamp::Now()) {
        waitTime = uint32_t((t - TimeStamp::Now()).ToMilliseconds());
      }
      PR_Sleep(PR_MillisecondsToInterval(waitTime));
    } while(true);

    nsresult rv;
    mBefore = TimeStamp::Now();
    mMiddle = mBefore + TimeDuration::FromMilliseconds(
        kTimerOffset + kTimerInterval * kNumTimers / 2);
    for (uint32_t i = 0; i < kNumTimers; ++i) {
      nsCOMPtr<nsITimer> timer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
      ASSERT_TRUE(NS_SUCCEEDED(rv));

      if (i < aNumDifferingTimers) {
        if (aTarget) {
          timer->SetTarget(aTarget);
        }

        timer->InitWithFuncCallback(&UnusedCallbackFunc,
                                    nullptr,
                                    kTimerOffset + kTimerInterval * i,
                                    aType);
      } else {
        timer->InitWithFuncCallback(&UnusedCallbackFunc,
                                    nullptr,
                                    kTimerOffset + kTimerInterval * i,
                                    nsITimer::TYPE_ONE_SHOT);
      }
      mTimers.push_front(timer.get());
    }
  }

  static void UnusedCallbackFunc(nsITimer* aTimer, void* aClosure)
  {
    FAIL() << "Timer shouldn't fire.";
  }
};

TEST(Timers, FindExpirationTime)
{
  {
    FindExpirationTimeState state;
    // 0 low priority timers
    state.InitTimers(0, nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY);
    TimeStamp before = state.mBefore;
    TimeStamp middle = state.mMiddle;

    TimeStamp t;
    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 10);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";
  }

  {
    FindExpirationTimeState state;
    // 5 low priority timers
    state.InitTimers(5, nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY);
    TimeStamp before = state.mBefore;
    TimeStamp middle = state.mMiddle;

    TimeStamp t;
    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 10);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";
  }

  {
    FindExpirationTimeState state;
    // 15 low priority timers
    state.InitTimers(15, nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY);
    TimeStamp before = state.mBefore;
    TimeStamp middle = state.mMiddle;

    TimeStamp t;
    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 10);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, middle) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, middle) << "Found time should be equal to default";
  }

  {
    AutoTestThread testThread;
    FindExpirationTimeState state;
    // 5 other targets
    state.InitTimers(5, static_cast<nsIEventTarget*>(testThread));
    TimeStamp before = state.mBefore;
    TimeStamp middle = state.mMiddle;

    TimeStamp t;
    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 10);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";
  }

  {
    AutoTestThread testThread;
    FindExpirationTimeState state;
    // 15 other targets
    state.InitTimers(15, static_cast<nsIEventTarget*>(testThread));
    TimeStamp before = state.mBefore;
    TimeStamp middle = state.mMiddle;

    TimeStamp t;
    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(before, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, before) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 0);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_LT(t, middle) << "Found time should be less than default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 10);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, middle) << "Found time should be equal to default";

    t = NS_GetTimerDeadlineHintOnCurrentThread(middle, 20);
    EXPECT_TRUE(t) << "We should find a time";
    EXPECT_EQ(t, middle) << "Found time should be equal to default";
  }
}

#endif

#define FUZZ_MAX_TIMEOUT 9
class FuzzTestThreadState final : public nsITimerCallback {
  public:
    NS_DECL_THREADSAFE_ISUPPORTS

    explicit FuzzTestThreadState(nsIThread* thread) :
      mThread(thread),
      mStopped(false)
    {}

    class StartRunnable final : public mozilla::Runnable {
      public:
        explicit StartRunnable(FuzzTestThreadState* threadState) :
          mThreadState(threadState)
        {}

        NS_IMETHOD Run() override
        {
          mThreadState->ScheduleOrCancelTimers();
          return NS_OK;
        }

      private:
        RefPtr<FuzzTestThreadState> mThreadState;
    };

    void Start()
    {
      nsCOMPtr<nsIRunnable> runnable = new StartRunnable(this);
      nsresult rv = mThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "Failed to dispatch StartRunnable.");
    }

    void Stop()
    {
      mStopped = true;
    }

    NS_IMETHOD Notify(nsITimer* aTimer) override
    {
      bool onCorrectThread;
      nsresult rv = mThread->IsOnCurrentThread(&onCorrectThread);
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "Failed to perform thread check.");
      MOZ_RELEASE_ASSERT(onCorrectThread, "Notify invoked on wrong thread.");

      uint32_t delay;
      rv = aTimer->GetDelay(&delay);
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "GetDelay failed.");

      MOZ_RELEASE_ASSERT(delay <= FUZZ_MAX_TIMEOUT,
                         "Delay was an invalid value for this test.");

      uint32_t type;
      rv = aTimer->GetType(&type);
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "Failed to get timer type.");
      MOZ_RELEASE_ASSERT(type <= nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP);

      if (type == nsITimer::TYPE_ONE_SHOT) {
        MOZ_RELEASE_ASSERT(!mOneShotTimersByDelay[delay].empty(),
                           "Unexpected one-shot timer.");

        MOZ_RELEASE_ASSERT(mOneShotTimersByDelay[delay].front().get() == aTimer,
                           "One-shot timers have been reordered.");

        mOneShotTimersByDelay[delay].pop_front();
        --mTimersOutstanding;
      } else if (mStopped) {
        CancelRepeatingTimer(aTimer);
      }

      ScheduleOrCancelTimers();
      RescheduleSomeTimers();
      return NS_OK;
    }

    bool HasTimersOutstanding() const
    {
      return !!mTimersOutstanding;
    }

  private:
    ~FuzzTestThreadState()
    {
      for (size_t i = 0; i <= FUZZ_MAX_TIMEOUT; ++i) {
        MOZ_RELEASE_ASSERT(mOneShotTimersByDelay[i].empty(),
                           "Timers remain at end of test.");
      }
    }

    uint32_t GetRandomType() const
    {
      return rand() % (nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP + 1);
    }

    size_t CountOneShotTimers() const
    {
      size_t count = 0;
      for (size_t i = 0; i <= FUZZ_MAX_TIMEOUT; ++i) {
        count += mOneShotTimersByDelay[i].size();
      }
      return count;
    }

    void ScheduleOrCancelTimers()
    {
      if (mStopped) {
        return;
      }

      const size_t numTimersDesired = (rand() % 100) + 100;
      MOZ_RELEASE_ASSERT(numTimersDesired >= 100);
      MOZ_RELEASE_ASSERT(numTimersDesired < 200);
      int adjustment = numTimersDesired - mTimersOutstanding;

      while (adjustment > 0) {
        CreateRandomTimer();
        --adjustment;
      }

      while (adjustment < 0) {
        CancelRandomTimer();
        ++adjustment;
      }

      MOZ_RELEASE_ASSERT(numTimersDesired == mTimersOutstanding);
    }

    void RescheduleSomeTimers()
    {
      if (mStopped) {
        return;
      }

      static const size_t kNumRescheduled = 40;

      // Reschedule some timers with a Cancel first.
      for (size_t i = 0; i < kNumRescheduled; ++i) {
        InitRandomTimer(CancelRandomTimer().get());
      }
      // Reschedule some timers without a Cancel first.
      for (size_t i = 0; i < kNumRescheduled; ++i) {
        InitRandomTimer(RemoveRandomTimer().get());
      }
    }

    void CreateRandomTimer()
    {
      nsresult rv;
      nsCOMPtr<nsITimer> timer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "Failed to create timer.");

      rv = timer->SetTarget(static_cast<nsIEventTarget*>(mThread.get()));
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "Failed to set target.");

      InitRandomTimer(timer.get());
    }

    nsCOMPtr<nsITimer> CancelRandomTimer()
    {
      nsCOMPtr<nsITimer> timer(RemoveRandomTimer());
      timer->Cancel();
      return timer;
    }

    nsCOMPtr<nsITimer> RemoveRandomTimer()
    {
      MOZ_RELEASE_ASSERT(mTimersOutstanding);

      if ((GetRandomType() == nsITimer::TYPE_ONE_SHOT && CountOneShotTimers())
          || mRepeatingTimers.empty()) {
        uint32_t delayToRemove = rand() % (FUZZ_MAX_TIMEOUT + 1);
        while (mOneShotTimersByDelay[delayToRemove].empty()) {
          // ++delayToRemove mod FUZZ_MAX_TIMEOUT + 1
          delayToRemove = (delayToRemove + 1) % (FUZZ_MAX_TIMEOUT + 1);
        }

        uint32_t indexToRemove =
          rand() % mOneShotTimersByDelay[delayToRemove].size();

        for (auto it = mOneShotTimersByDelay[delayToRemove].begin();
             it != mOneShotTimersByDelay[delayToRemove].end();
             ++it) {
          if (indexToRemove) {
            --indexToRemove;
            continue;
          }

          nsCOMPtr<nsITimer> removed = *it;
          mOneShotTimersByDelay[delayToRemove].erase(it);
          --mTimersOutstanding;
          return removed;
        }
      } else {
        size_t indexToRemove = rand() % mRepeatingTimers.size();
        nsCOMPtr<nsITimer> removed(mRepeatingTimers[indexToRemove]);
        mRepeatingTimers.erase(mRepeatingTimers.begin() + indexToRemove);
        --mTimersOutstanding;
        return removed;
      }

      MOZ_CRASH("Unable to remove a timer");
    }

    void InitRandomTimer(nsITimer* aTimer)
    {
      // Between 0 and FUZZ_MAX_TIMEOUT
      uint32_t delay = rand() % (FUZZ_MAX_TIMEOUT + 1);
      uint32_t type = GetRandomType();
      nsresult rv = aTimer->InitWithCallback(this, delay, type);
      MOZ_RELEASE_ASSERT(NS_SUCCEEDED(rv), "Failed to set timer.");

      if (type == nsITimer::TYPE_ONE_SHOT) {
        mOneShotTimersByDelay[delay].push_back(aTimer);
      } else {
        mRepeatingTimers.push_back(aTimer);
      }
      ++mTimersOutstanding;
    }

    void CancelRepeatingTimer(nsITimer* aTimer)
    {
      for (auto it = mRepeatingTimers.begin();
           it != mRepeatingTimers.end();
           ++it) {
        if (it->get() == aTimer) {
          mRepeatingTimers.erase(it);
          aTimer->Cancel();
          --mTimersOutstanding;
          return;
        }
      }
    }

    nsCOMPtr<nsIThread> mThread;
    // Scheduled timers, indexed by delay between 0-9 ms, in lists
    // with most recently scheduled last.
    std::list<nsCOMPtr<nsITimer>> mOneShotTimersByDelay[FUZZ_MAX_TIMEOUT + 1];
    std::vector<nsCOMPtr<nsITimer>> mRepeatingTimers;
    Atomic<bool> mStopped;
    Atomic<size_t> mTimersOutstanding;
};

NS_IMPL_ISUPPORTS(FuzzTestThreadState, nsITimerCallback)

TEST(Timers, FuzzTestTimers)
{
  static const size_t kNumThreads(10);
  AutoTestThread threads[kNumThreads];
  RefPtr<FuzzTestThreadState> threadStates[kNumThreads];

  for (size_t i = 0; i < kNumThreads; ++i) {
    threadStates[i] = new FuzzTestThreadState(&*threads[i]);
    threadStates[i]->Start();
  }

  PR_Sleep(PR_MillisecondsToInterval(20000));

  for (size_t i = 0; i < kNumThreads; ++i) {
    threadStates[i]->Stop();
  }

  // Wait at most 10 seconds for all outstanding timers to pop
  PRIntervalTime start = PR_IntervalNow();
  for (auto& threadState : threadStates) {
    while (threadState->HasTimersOutstanding()) {
      uint32_t elapsedMs = PR_IntervalToMilliseconds(PR_IntervalNow() - start);
      ASSERT_LE(elapsedMs, uint32_t(10000)) << "Timed out waiting for all timers to pop";
      PR_Sleep(PR_MillisecondsToInterval(10));
    }
  }
}