From 26a029d407be480d791972afb5975cf62c9360a6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Fri, 19 Apr 2024 02:47:55 +0200 Subject: Adding upstream version 124.0.1. Signed-off-by: Daniel Baumann --- xpcom/threads/TimerThread.cpp | 1565 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1565 insertions(+) create mode 100644 xpcom/threads/TimerThread.cpp (limited to 'xpcom/threads/TimerThread.cpp') diff --git a/xpcom/threads/TimerThread.cpp b/xpcom/threads/TimerThread.cpp new file mode 100644 index 0000000000..d0ff778f20 --- /dev/null +++ b/xpcom/threads/TimerThread.cpp @@ -0,0 +1,1565 @@ +/* -*- 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 "GeckoProfiler.h" +#include "nsThreadUtils.h" + +#include "nsIObserverService.h" +#include "nsIPropertyBag2.h" +#include "mozilla/Services.h" +#include "mozilla/ChaosMode.h" +#include "mozilla/ArenaAllocator.h" +#include "mozilla/ArrayUtils.h" +#include "mozilla/OperatorNewExtensions.h" +#include "mozilla/StaticPrefs_timer.h" + +#include "mozilla/glean/GleanMetrics.h" + +#include + +using namespace mozilla; + +#ifdef XP_WIN +// Include Windows header required for enabling high-precision timers. +# include +# include + +static constexpr UINT kTimerPeriodHiRes = 1; +static constexpr UINT kTimerPeriodLowRes = 16; + +// Helper functions to determine what Windows timer resolution to target. +static constexpr UINT GetDesiredTimerPeriod(const bool aOnBatteryPower, + const bool aLowProcessPriority) { + const bool useLowResTimer = aOnBatteryPower || aLowProcessPriority; + return useLowResTimer ? kTimerPeriodLowRes : kTimerPeriodHiRes; +} + +static_assert(GetDesiredTimerPeriod(true, false) == kTimerPeriodLowRes); +static_assert(GetDesiredTimerPeriod(false, true) == kTimerPeriodLowRes); +static_assert(GetDesiredTimerPeriod(true, true) == kTimerPeriodLowRes); +static_assert(GetDesiredTimerPeriod(false, false) == kTimerPeriodHiRes); + +UINT TimerThread::ComputeDesiredTimerPeriod() const { + const bool lowPriorityProcess = + mCachedPriority.load(std::memory_order_relaxed) < + hal::PROCESS_PRIORITY_FOREGROUND; + + // NOTE: Using short-circuiting here to avoid call to GetSystemPowerStatus() + // when we know that that result will not affect the final result. (As + // confirmed by the static_assert's above, onBatteryPower does not affect the + // result when the lowPriorityProcess is true.) + SYSTEM_POWER_STATUS status; + const bool onBatteryPower = !lowPriorityProcess && + GetSystemPowerStatus(&status) && + (status.ACLineStatus == 0); + + return GetDesiredTimerPeriod(onBatteryPower, lowPriorityProcess); +} +#endif + +// Uncomment the following line to enable runtime stats during development. +// #define TIMERS_RUNTIME_STATS + +#ifdef TIMERS_RUNTIME_STATS +// This class gathers durations and displays some basic stats when destroyed. +// It is intended to be used as a static variable (see `AUTO_TIMERS_STATS` +// below), to display stats at the end of the program. +class StaticTimersStats { + public: + explicit StaticTimersStats(const char* aName) : mName(aName) {} + + ~StaticTimersStats() { + // Using unsigned long long for computations and printfs. + using ULL = unsigned long long; + ULL n = static_cast(mCount); + if (n == 0) { + printf("[%d] Timers stats `%s`: (nothing)\n", + int(profiler_current_process_id().ToNumber()), mName); + } else if (ULL sumNs = static_cast(mSumDurationsNs); sumNs == 0) { + printf("[%d] Timers stats `%s`: %llu\n", + int(profiler_current_process_id().ToNumber()), mName, n); + } else { + printf("[%d] Timers stats `%s`: %llu ns / %llu = %llu ns, max %llu ns\n", + int(profiler_current_process_id().ToNumber()), mName, sumNs, n, + sumNs / n, static_cast(mLongestDurationNs)); + } + } + + void AddDurationFrom(TimeStamp aStart) { + // Duration between aStart and now, rounded to the nearest nanosecond. + DurationNs duration = static_cast( + (TimeStamp::Now() - aStart).ToMicroseconds() * 1000 + 0.5); + mSumDurationsNs += duration; + ++mCount; + // Update mLongestDurationNs if this one is longer. + for (;;) { + DurationNs longest = mLongestDurationNs; + if (MOZ_LIKELY(longest >= duration)) { + // This duration is not the longest, nothing to do. + break; + } + if (MOZ_LIKELY(mLongestDurationNs.compareExchange(longest, duration))) { + // Successfully updated `mLongestDurationNs` with the new value. + break; + } + // Otherwise someone else just updated `mLongestDurationNs`, we need to + // try again by looping. + } + } + + void AddCount() { + MOZ_ASSERT(mSumDurationsNs == 0, "Don't mix counts and durations"); + ++mCount; + } + + private: + using DurationNs = uint64_t; + using Count = uint32_t; + + Atomic mSumDurationsNs{0}; + Atomic mLongestDurationNs{0}; + Atomic mCount{0}; + const char* mName; +}; + +// RAII object that measures its scoped lifetime duration and reports it to a +// `StaticTimersStats`. +class MOZ_RAII AutoTimersStats { + public: + explicit AutoTimersStats(StaticTimersStats& aStats) + : mStats(aStats), mStart(TimeStamp::Now()) {} + + ~AutoTimersStats() { mStats.AddDurationFrom(mStart); } + + private: + StaticTimersStats& mStats; + TimeStamp mStart; +}; + +// Macro that should be used to collect basic statistics from measurements of +// block durations, from where this macro is, until the end of its enclosing +// scope. The name is used in the static variable name and when displaying stats +// at the end of the program; Another location could use the same name but their +// stats will not be combined, so use different name if these locations should +// be distinguished. +# define AUTO_TIMERS_STATS(name) \ + static ::StaticTimersStats sStat##name(#name); \ + ::AutoTimersStats autoStat##name(sStat##name); + +// This macro only counts the number of times it's used, not durations. +// Don't mix with AUTO_TIMERS_STATS! +# define COUNT_TIMERS_STATS(name) \ + static ::StaticTimersStats sStat##name(#name); \ + sStat##name.AddCount(); + +#else // TIMERS_RUNTIME_STATS + +# define AUTO_TIMERS_STATS(name) +# define COUNT_TIMERS_STATS(name) + +#endif // TIMERS_RUNTIME_STATS else + +NS_IMPL_ISUPPORTS_INHERITED(TimerThread, Runnable, nsIObserver) + +TimerThread::TimerThread() + : Runnable("TimerThread"), + mInitialized(false), + mMonitor("TimerThread.mMonitor"), + mShutdown(false), + mWaiting(false), + mNotified(false), + mSleeping(false), + mAllowedEarlyFiringMicroseconds(0) {} + +TimerThread::~TimerThread() { + mThread = nullptr; + + NS_ASSERTION(mTimers.IsEmpty(), "Timers remain in TimerThread::~TimerThread"); + +#if TIMER_THREAD_STATISTICS + { + MonitorAutoLock lock(mMonitor); + PrintStatistics(); + } +#endif +} + +namespace { + +class TimerObserverRunnable : public Runnable { + public: + explicit TimerObserverRunnable(nsIObserver* aObserver) + : mozilla::Runnable("TimerObserverRunnable"), mObserver(aObserver) {} + + NS_DECL_NSIRUNNABLE + + private: + nsCOMPtr mObserver; +}; + +NS_IMETHODIMP +TimerObserverRunnable::Run() { + nsCOMPtr 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); + observerService->AddObserver(mObserver, "ipc:process-priority-changed", + 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 is layered over ArenaAllocator, 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; + }; + + ArenaAllocator<4096> mPool MOZ_GUARDED_BY(mMonitor); + FreeEntry* mFirstFree MOZ_GUARDED_BY(mMonitor); + mozilla::Monitor mMonitor; + + public: + TimerEventAllocator() + : mFirstFree(nullptr), mMonitor("TimerEventAllocator") {} + + ~TimerEventAllocator() = default; + + 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 { + mTimer->Cancel(); + return NS_OK; + } + +#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY + NS_IMETHOD GetName(nsACString& aName) override; +#endif + + explicit nsTimerEvent(already_AddRefed aTimer, + ProfilerThreadId aTimerThreadId) + : mozilla::CancelableRunnable("nsTimerEvent"), + mTimer(aTimer), + mGeneration(mTimer->GetGeneration()), + mTimerThreadId(aTimerThreadId) { + // Note: We override operator new for this class, and the override is + // fallible! + sAllocatorUsers++; + + if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug) || + profiler_thread_is_being_profiled_for_markers(mTimerThreadId)) { + mInitTime = TimeStamp::Now(); + } + } + + static void Init(); + static void Shutdown(); + static void DeleteAllocatorIfNeeded(); + + static void* operator new(size_t aSize) noexcept(true) { + return sAllocator->Alloc(aSize); + } + void operator delete(void* aPtr) { + sAllocator->Free(aPtr); + sAllocatorUsers--; + DeleteAllocatorIfNeeded(); + } + + already_AddRefed ForgetTimer() { return mTimer.forget(); } + + 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"); + } + + TimeStamp mInitTime; + RefPtr mTimer; + const int32_t mGeneration; + ProfilerThreadId mTimerThreadId; + + static TimerEventAllocator* sAllocator; + + static Atomic sAllocatorUsers; + static Atomic sCanDeleteAllocator; +}; + +TimerEventAllocator* nsTimerEvent::sAllocator = nullptr; +Atomic nsTimerEvent::sAllocatorUsers; +Atomic nsTimerEvent::sCanDeleteAllocator; + +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 { + p = mPool.Allocate(aSize, fallible); + } + + return p; +} + +void TimerEventAllocator::Free(void* aPtr) { + mozilla::MonitorAutoLock lock(mMonitor); + + FreeEntry* entry = reinterpret_cast(aPtr); + + entry->mNext = mFirstFree; + mFirstFree = entry; +} + +} // namespace + +struct TimerMarker { + static constexpr Span MarkerTypeName() { + return MakeStringSpan("Timer"); + } + static void StreamJSONMarkerData(baseprofiler::SpliceableJSONWriter& aWriter, + uint32_t aDelay, uint8_t aType, + MarkerThreadId aThreadId, bool aCanceled) { + aWriter.IntProperty("delay", aDelay); + if (!aThreadId.IsUnspecified()) { + // Tech note: If `ToNumber()` returns a uint64_t, the conversion to + // int64_t is "implementation-defined" before C++20. This is + // acceptable here, because this is a one-way conversion to a unique + // identifier that's used to visually separate data by thread on the + // front-end. + aWriter.IntProperty( + "threadId", static_cast(aThreadId.ThreadId().ToNumber())); + } + if (aCanceled) { + aWriter.BoolProperty("canceled", true); + // Show a red 'X' as a prefix on the marker chart for canceled timers. + aWriter.StringProperty("prefix", "❌"); + } + + // The string property for the timer type is not written when the type is + // one shot, as that's the type used almost all the time, and that would + // consume space in the profiler buffer and then in the profile JSON, + // getting in the way of capturing long power profiles. + // Bug 1815677 might make this cheap to capture. + if (aType != nsITimer::TYPE_ONE_SHOT) { + if (aType == nsITimer::TYPE_REPEATING_SLACK) { + aWriter.StringProperty("ttype", "repeating slack"); + } else if (aType == nsITimer::TYPE_REPEATING_PRECISE) { + aWriter.StringProperty("ttype", "repeating precise"); + } else if (aType == nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP) { + aWriter.StringProperty("ttype", "repeating precise can skip"); + } else if (aType == nsITimer::TYPE_REPEATING_SLACK_LOW_PRIORITY) { + aWriter.StringProperty("ttype", "repeating slack low priority"); + } else if (aType == nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY) { + aWriter.StringProperty("ttype", "low priority"); + } + } + } + static MarkerSchema MarkerTypeDisplay() { + using MS = MarkerSchema; + MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable}; + schema.AddKeyLabelFormat("delay", "Delay", MS::Format::Milliseconds); + schema.AddKeyLabelFormat("ttype", "Timer Type", MS::Format::String); + schema.AddKeyLabelFormat("canceled", "Canceled", MS::Format::String); + schema.SetChartLabel("{marker.data.prefix} {marker.data.delay}"); + schema.SetTableLabel( + "{marker.name} - {marker.data.prefix} {marker.data.delay}"); + return schema; + } +}; + +struct AddRemoveTimerMarker { + static constexpr Span MarkerTypeName() { + return MakeStringSpan("AddRemoveTimer"); + } + static void StreamJSONMarkerData(baseprofiler::SpliceableJSONWriter& aWriter, + const ProfilerString8View& aTimerName, + uint32_t aDelay, MarkerThreadId aThreadId) { + aWriter.StringProperty("name", aTimerName); + aWriter.IntProperty("delay", aDelay); + if (!aThreadId.IsUnspecified()) { + // Tech note: If `ToNumber()` returns a uint64_t, the conversion to + // int64_t is "implementation-defined" before C++20. This is + // acceptable here, because this is a one-way conversion to a unique + // identifier that's used to visually separate data by thread on the + // front-end. + aWriter.IntProperty( + "threadId", static_cast(aThreadId.ThreadId().ToNumber())); + } + } + static MarkerSchema MarkerTypeDisplay() { + using MS = MarkerSchema; + MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable}; + schema.AddKeyLabelFormatSearchable("name", "Name", MS::Format::String, + MS::Searchable::Searchable); + schema.AddKeyLabelFormat("delay", "Delay", MS::Format::Milliseconds); + schema.SetTableLabel( + "{marker.name} - {marker.data.name} - {marker.data.delay}"); + return schema; + } +}; + +void nsTimerEvent::Init() { sAllocator = new TimerEventAllocator(); } + +void nsTimerEvent::Shutdown() { + sCanDeleteAllocator = true; + DeleteAllocatorIfNeeded(); +} + +void nsTimerEvent::DeleteAllocatorIfNeeded() { + if (sCanDeleteAllocator && sAllocatorUsers == 0) { + delete sAllocator; + sAllocator = nullptr; + } +} + +#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY +NS_IMETHODIMP +nsTimerEvent::GetName(nsACString& aName) { + bool current; + MOZ_RELEASE_ASSERT( + NS_SUCCEEDED(mTimer->mEventTarget->IsOnCurrentThread(¤t)) && + current); + + mTimer->GetName(aName); + return NS_OK; +} +#endif + +NS_IMETHODIMP +nsTimerEvent::Run() { + 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())); + } + + if (profiler_thread_is_being_profiled_for_markers(mTimerThreadId)) { + MutexAutoLock lock(mTimer->mMutex); + nsAutoCString name; + mTimer->GetName(name, lock); + // This adds a marker with the timer name as the marker name, to make it + // obvious which timers are being used. This marker will be useful to + // understand which timers might be added and firing excessively often. + profiler_add_marker( + name, geckoprofiler::category::TIMER, + MarkerOptions(MOZ_LIKELY(mInitTime) + ? MarkerTiming::Interval( + mTimer->mTimeout - mTimer->mDelay, mInitTime) + : MarkerTiming::IntervalUntilNowFrom( + mTimer->mTimeout - mTimer->mDelay), + MarkerThreadId(mTimerThreadId)), + TimerMarker{}, mTimer->mDelay.ToMilliseconds(), mTimer->mType, + MarkerThreadId::CurrentThread(), false); + // This marker is meant to help understand the behavior of the timer thread. + profiler_add_marker( + "PostTimerEvent", geckoprofiler::category::OTHER, + MarkerOptions(MOZ_LIKELY(mInitTime) + ? MarkerTiming::IntervalUntilNowFrom(mInitTime) + : MarkerTiming::InstantNow(), + MarkerThreadId(mTimerThreadId)), + AddRemoveTimerMarker{}, name, mTimer->mDelay.ToMilliseconds(), + MarkerThreadId::CurrentThread()); + } + + mTimer->Fire(mGeneration); + + return NS_OK; +} + +nsresult TimerThread::Init() { + mMonitor.AssertCurrentThreadOwns(); + MOZ_LOG(GetTimerLog(), LogLevel::Debug, + ("TimerThread::Init [%d]\n", mInitialized)); + + if (!mInitialized) { + nsTimerEvent::Init(); + + // We hold on to mThread to keep the thread alive. + nsresult rv = + NS_NewNamedThread("Timer", getter_AddRefs(mThread), this, + {.stackSize = nsIThreadManager::DEFAULT_STACK_SIZE, + .blockDispatch = true}); + if (NS_FAILED(rv)) { + mThread = nullptr; + } else { + RefPtr r = new TimerObserverRunnable(this); + if (NS_IsMainThread()) { + r->Run(); + } else { + NS_DispatchToMainThread(r); + } + } + + mInitialized = true; + } + + 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> 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.SetCapacity(mTimers.Length()); + for (Entry& entry : mTimers) { + if (entry.Value()) { + timers.AppendElement(entry.Take()); + } + } + + mTimers.Clear(); + } + + for (const RefPtr& timer : timers) { + MOZ_ASSERT(timer); + timer->Cancel(); + } + + 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 + +#ifdef DEBUG +void TimerThread::VerifyTimerListConsistency() const { + mMonitor.AssertCurrentThreadOwns(); + + // Find the first non-canceled timer (and check its cached timeout if we find + // it). + const size_t timerCount = mTimers.Length(); + size_t lastNonCanceledTimerIndex = 0; + while (lastNonCanceledTimerIndex < timerCount && + !mTimers[lastNonCanceledTimerIndex].Value()) { + ++lastNonCanceledTimerIndex; + } + MOZ_ASSERT(lastNonCanceledTimerIndex == timerCount || + mTimers[lastNonCanceledTimerIndex].Value()); + MOZ_ASSERT(lastNonCanceledTimerIndex == timerCount || + mTimers[lastNonCanceledTimerIndex].Value()->mTimeout == + mTimers[lastNonCanceledTimerIndex].Timeout()); + + // Verify that mTimers is sorted and the cached timeouts are consistent. + for (size_t timerIndex = lastNonCanceledTimerIndex + 1; + timerIndex < timerCount; ++timerIndex) { + if (mTimers[timerIndex].Value()) { + MOZ_ASSERT(mTimers[timerIndex].Timeout() == + mTimers[timerIndex].Value()->mTimeout); + MOZ_ASSERT(mTimers[timerIndex].Timeout() >= + mTimers[lastNonCanceledTimerIndex].Timeout()); + lastNonCanceledTimerIndex = timerIndex; + } + } +} +#endif + +size_t TimerThread::ComputeTimerInsertionIndex(const TimeStamp& timeout) const { + mMonitor.AssertCurrentThreadOwns(); + + const size_t timerCount = mTimers.Length(); + + size_t firstGtIndex = 0; + while (firstGtIndex < timerCount && + (!mTimers[firstGtIndex].Value() || + mTimers[firstGtIndex].Timeout() <= timeout)) { + ++firstGtIndex; + } + + return firstGtIndex; +} + +TimeStamp TimerThread::ComputeWakeupTimeFromTimers() const { + mMonitor.AssertCurrentThreadOwns(); + + // Timer list should be non-empty and first timer should always be + // non-canceled at this point and we rely on that here. + MOZ_ASSERT(!mTimers.IsEmpty()); + MOZ_ASSERT(mTimers[0].Value()); + + // Overview: Find the last timer in the list that can be "bundled" together in + // the same wake-up with mTimers[0] and use its timeout as our target wake-up + // time. + + // bundleWakeup is when we should wake up in order to be able to fire all of + // the timers in our selected bundle. It will always be the timeout of the + // last timer in the bundle. + TimeStamp bundleWakeup = mTimers[0].Timeout(); + + // cutoffTime is the latest that we can wake up for the timers currently + // accepted into the bundle. These needs to be updated as we go through the + // list because later timers may have more strict delay tolerances. + const TimeDuration minTimerDelay = TimeDuration::FromMilliseconds( + StaticPrefs::timer_minimum_firing_delay_tolerance_ms()); + const TimeDuration maxTimerDelay = TimeDuration::FromMilliseconds( + StaticPrefs::timer_maximum_firing_delay_tolerance_ms()); + TimeStamp cutoffTime = + bundleWakeup + ComputeAcceptableFiringDelay(mTimers[0].Delay(), + minTimerDelay, maxTimerDelay); + + const size_t timerCount = mTimers.Length(); + for (size_t entryIndex = 1; entryIndex < timerCount; ++entryIndex) { + const Entry& curEntry = mTimers[entryIndex]; + const nsTimerImpl* curTimer = curEntry.Value(); + if (!curTimer) { + // Canceled timer - skip it + continue; + } + + const TimeStamp curTimerDue = curEntry.Timeout(); + if (curTimerDue > cutoffTime) { + // Can't include this timer in the bundle - it fires too late. + break; + } + + // This timer can be included in the bundle. Update bundleWakeup and + // cutoffTime. + bundleWakeup = curTimerDue; + cutoffTime = std::min( + curTimerDue + ComputeAcceptableFiringDelay( + curEntry.Delay(), minTimerDelay, maxTimerDelay), + cutoffTime); + MOZ_ASSERT(bundleWakeup <= cutoffTime); + } + +#if !defined(XP_WIN) + // Due to the fact that, on Windows, each TimeStamp object holds two distinct + // "values", this assert is not valid there. See bug 1829983 for the details. + MOZ_ASSERT(bundleWakeup - mTimers[0].Timeout() <= + ComputeAcceptableFiringDelay(mTimers[0].Delay(), minTimerDelay, + maxTimerDelay)); +#endif + + return bundleWakeup; +} + +TimeDuration TimerThread::ComputeAcceptableFiringDelay( + TimeDuration timerDuration, TimeDuration minDelay, + TimeDuration maxDelay) const { + // Use the timer's duration divided by this value as a base for how much + // firing delay a timer can accept. 8 was chosen specifically because it is a + // power of two which means that this division turns nicely into a shift. + constexpr int64_t timerDurationDivider = 8; + static_assert(IsPowerOfTwo(static_cast(timerDurationDivider))); + const TimeDuration tmp = timerDuration / timerDurationDivider; + return std::min(std::max(minDelay, tmp), maxDelay); +} + +NS_IMETHODIMP +TimerThread::Run() { + MonitorAutoLock lock(mMonitor); + + mProfilerThreadId = profiler_current_thread_id(); + + // TODO: Make mAllowedEarlyFiringMicroseconds const and initialize it in the + // constructor. + mAllowedEarlyFiringMicroseconds = 250; + const TimeDuration allowedEarlyFiring = + TimeDuration::FromMicroseconds(mAllowedEarlyFiringMicroseconds); + + bool forceRunNextTimer = false; + + // Queue for tracking of how many timers are fired on each wake-up. We need to + // buffer these locally and only send off to glean occasionally to avoid + // performance hit. + static constexpr size_t kMaxQueuedTimerFired = 128; + size_t queuedTimerFiredCount = 0; + AutoTArray queuedTimersFiredPerWakeup; + queuedTimersFiredPerWakeup.SetLengthAndRetainStorage(kMaxQueuedTimerFired); + +#ifdef XP_WIN + // kTimerPeriodEvalIntervalSec is the minimum amount of time that must pass + // before we will consider changing the timer period again. + static constexpr float kTimerPeriodEvalIntervalSec = 2.0f; + const TimeDuration timerPeriodEvalInterval = + TimeDuration::FromSeconds(kTimerPeriodEvalIntervalSec); + TimeStamp nextTimerPeriodEval = TimeStamp::Now() + timerPeriodEvalInterval; + + // If this is false, we will perform all of the logic but will stop short of + // actually changing the timer period. + const bool adjustTimerPeriod = + StaticPrefs::timer_auto_increase_timer_resolution(); + UINT lastTimePeriodSet = ComputeDesiredTimerPeriod(); + + if (adjustTimerPeriod) { + timeBeginPeriod(lastTimePeriodSet); + } +#endif + + uint64_t timersFiredThisWakeup = 0; + while (!mShutdown) { + // Have to use PRIntervalTime here, since PR_WaitCondVar takes it + TimeDuration waitFor; + bool forceRunThisTimer = forceRunNextTimer; + forceRunNextTimer = false; + +#ifdef DEBUG + VerifyTimerListConsistency(); +#endif + + 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 = TimeDuration::FromMilliseconds(milliseconds); + } else { + waitFor = TimeDuration::Forever(); + TimeStamp now = TimeStamp::Now(); + +#ifdef XP_WIN + if (now >= nextTimerPeriodEval) { + const UINT newTimePeriod = ComputeDesiredTimerPeriod(); + if (newTimePeriod != lastTimePeriodSet) { + if (adjustTimerPeriod) { + timeEndPeriod(lastTimePeriodSet); + timeBeginPeriod(newTimePeriod); + } + lastTimePeriodSet = newTimePeriod; + } + nextTimerPeriodEval = now + timerPeriodEvalInterval; + } +#endif + +#if TIMER_THREAD_STATISTICS + if (!mNotified && !mIntendedWakeupTime.IsNull() && + now < mIntendedWakeupTime) { + ++mEarlyWakeups; + const double earlinessms = (mIntendedWakeupTime - now).ToMilliseconds(); + mTotalEarlyWakeupTime += earlinessms; + } +#endif + + RemoveLeadingCanceledTimersInternal(); + + if (!mTimers.IsEmpty()) { + if (now + allowedEarlyFiring >= mTimers[0].Value()->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 timerRef(mTimers[0].Take()); + RemoveFirstTimerInternal(); + 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. + { + ++timersFiredThisWakeup; + LogTimerEvent::Run run(timerRef.get()); + PostTimerEvent(timerRef.forget()); + } + + 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(); + } + } + + RemoveLeadingCanceledTimersInternal(); + + if (!mTimers.IsEmpty()) { + TimeStamp timeout = mTimers[0].Value()->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 mAllowedEarlyFiringMicroseconds, 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).ToMicroseconds(); + + // 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 constexpr double sChaosFractions[] = {0.0, 0.25, 0.5, 0.75, + 1.0, 1.75, 2.75}; + if (ChaosMode::isActive(ChaosFeature::TimerScheduling)) { + microseconds *= sChaosFractions[ChaosMode::randomUint32LessThan( + ArrayLength(sChaosFractions))]; + forceRunNextTimer = true; + } + + if (microseconds < mAllowedEarlyFiringMicroseconds) { + forceRunNextTimer = false; + goto next; // round down; execute event now + } + + // TECHNICAL NOTE: Determining waitFor (by subtracting |now| from our + // desired wake-up time) at this point is not ideal. For one thing, the + // |now| that we have at this point is somewhat old. Secondly, there is + // quite a bit of code between here and where we actually use waitFor to + // request sleep. If I am thinking about this correctly, both of these + // will contribute to us requesting more sleep than is actually needed + // to wake up at our desired time. We could avoid this problem by only + // determining our desired wake-up time here and then calculating the + // wait time when we're actually about to sleep. + const TimeStamp wakeupTime = ComputeWakeupTimeFromTimers(); + waitFor = wakeupTime - now; + + // If this were to fail that would mean that we had more timers that we + // should have fired. + MOZ_ASSERT(!waitFor.IsZero()); + + if (ChaosMode::isActive(ChaosFeature::TimerScheduling)) { + // If chaos mode is active then mess with the amount of time that we + // request to sleep (without changing what we record as our expected + // wake-up time). This will simulate unintended early/late wake-ups. + const double waitInMs = waitFor.ToMilliseconds(); + const double chaosWaitInMs = + waitInMs * sChaosFractions[ChaosMode::randomUint32LessThan( + ArrayLength(sChaosFractions))]; + waitFor = TimeDuration::FromMilliseconds(chaosWaitInMs); + } + + mIntendedWakeupTime = wakeupTime; + } else { + mIntendedWakeupTime = TimeStamp{}; + } + + if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug)) { + if (waitFor == TimeDuration::Forever()) + MOZ_LOG(GetTimerLog(), LogLevel::Debug, ("waiting forever\n")); + else + MOZ_LOG(GetTimerLog(), LogLevel::Debug, + ("waiting for %f\n", waitFor.ToMilliseconds())); + } + } + + { + // About to sleep - let's make note of how many timers we processed and + // see if we should send out a new batch of telemetry. + queuedTimersFiredPerWakeup[queuedTimerFiredCount] = timersFiredThisWakeup; + ++queuedTimerFiredCount; + if (queuedTimerFiredCount == kMaxQueuedTimerFired) { + glean::timer_thread::timers_fired_per_wakeup.AccumulateSamples( + queuedTimersFiredPerWakeup); + queuedTimerFiredCount = 0; + } + } + +#if TIMER_THREAD_STATISTICS + { + size_t bucketIndex = 0; + while (bucketIndex < sTimersFiredPerWakeupBucketCount - 1 && + timersFiredThisWakeup > + sTimersFiredPerWakeupThresholds[bucketIndex]) { + ++bucketIndex; + } + MOZ_ASSERT(bucketIndex < sTimersFiredPerWakeupBucketCount); + ++mTimersFiredPerWakeup[bucketIndex]; + + ++mTotalWakeupCount; + if (mNotified) { + ++mTimersFiredPerNotifiedWakeup[bucketIndex]; + ++mTotalNotifiedWakeupCount; + } else { + ++mTimersFiredPerUnnotifiedWakeup[bucketIndex]; + ++mTotalUnnotifiedWakeupCount; + } + } +#endif + + timersFiredThisWakeup = 0; + + mWaiting = true; + mNotified = false; + + { + AUTO_PROFILER_TRACING_MARKER("TimerThread", "Wait", OTHER); + mMonitor.Wait(waitFor); + } + if (mNotified) { + forceRunNextTimer = false; + } + mWaiting = false; + } + + // About to shut down - let's send out the final batch of timers fired counts. + if (queuedTimerFiredCount != 0) { + queuedTimersFiredPerWakeup.SetLengthAndRetainStorage(queuedTimerFiredCount); + glean::timer_thread::timers_fired_per_wakeup.AccumulateSamples( + queuedTimersFiredPerWakeup); + } + +#ifdef XP_WIN + // About to shut down - let's finish off the last time period that we set. + if (adjustTimerPeriod) { + timeEndPeriod(lastTimePeriodSet); + } +#endif + + return NS_OK; +} + +nsresult TimerThread::AddTimer(nsTimerImpl* aTimer, + const MutexAutoLock& aProofOfLock) { + MonitorAutoLock lock(mMonitor); + AUTO_TIMERS_STATS(TimerThread_AddTimer); + + if (!aTimer->mEventTarget) { + return NS_ERROR_NOT_INITIALIZED; + } + + nsresult rv = Init(); + if (NS_FAILED(rv)) { + return rv; + } + + // Awaken the timer thread if: + // - This timer needs to fire *before* the Timer Thread is scheduled to wake + // up. + // AND/OR + // - The delay is 0, which is usually meant to be run as soon as possible. + // Note: Even if the thread is scheduled to wake up now/soon, on some + // systems there could be a significant delay compared to notifying, which + // is almost immediate; and some users of 0-delay depend on it being this + // fast! + const TimeDuration minTimerDelay = TimeDuration::FromMilliseconds( + StaticPrefs::timer_minimum_firing_delay_tolerance_ms()); + const TimeDuration maxTimerDelay = TimeDuration::FromMilliseconds( + StaticPrefs::timer_maximum_firing_delay_tolerance_ms()); + const TimeDuration firingDelay = ComputeAcceptableFiringDelay( + aTimer->mDelay, minTimerDelay, maxTimerDelay); + const bool firingBeforeNextWakeup = + mIntendedWakeupTime.IsNull() || + (aTimer->mTimeout + firingDelay < mIntendedWakeupTime); + const bool wakeUpTimerThread = + mWaiting && (firingBeforeNextWakeup || aTimer->mDelay.IsZero()); + +#if TIMER_THREAD_STATISTICS + if (mTotalTimersAdded == 0) { + mFirstTimerAdded = TimeStamp::Now(); + } + ++mTotalTimersAdded; +#endif + + // Add the timer to our list. + if (!AddTimerInternal(*aTimer)) { + return NS_ERROR_OUT_OF_MEMORY; + } + + if (wakeUpTimerThread) { + mNotified = true; + mMonitor.Notify(); + } + + if (profiler_thread_is_being_profiled_for_markers(mProfilerThreadId)) { + nsAutoCString name; + aTimer->GetName(name, aProofOfLock); + + nsLiteralCString prefix("Anonymous_"); + profiler_add_marker( + "AddTimer", geckoprofiler::category::OTHER, + MarkerOptions(MarkerThreadId(mProfilerThreadId), + MarkerStack::MaybeCapture( + name.Equals("nonfunction:JS") || + StringHead(name, prefix.Length()) == prefix)), + AddRemoveTimerMarker{}, name, aTimer->mDelay.ToMilliseconds(), + MarkerThreadId::CurrentThread()); + } + + return NS_OK; +} + +nsresult TimerThread::RemoveTimer(nsTimerImpl* aTimer, + const MutexAutoLock& aProofOfLock) { + MonitorAutoLock lock(mMonitor); + AUTO_TIMERS_STATS(TimerThread_RemoveTimer); + + // 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; + } + +#if TIMER_THREAD_STATISTICS + ++mTotalTimersRemoved; +#endif + + // Note: The timer thread is *not* awoken. + // The removed-timer entry is just left null, and will be reused (by a new or + // re-set timer) or discarded (when the timer thread logic handles non-null + // timers around it). + // If this was the front timer, and in the unlikely case that its entry is not + // soon reused by a re-set timer, the timer thread will wake up at the + // previously-scheduled time, but will quickly notice that there is no actual + // pending timer, and will restart its wait until the following real timeout. + + if (profiler_thread_is_being_profiled_for_markers(mProfilerThreadId)) { + nsAutoCString name; + aTimer->GetName(name, aProofOfLock); + + nsLiteralCString prefix("Anonymous_"); + // This marker is meant to help understand the behavior of the timer thread. + profiler_add_marker( + "RemoveTimer", geckoprofiler::category::OTHER, + MarkerOptions(MarkerThreadId(mProfilerThreadId), + MarkerStack::MaybeCapture( + name.Equals("nonfunction:JS") || + StringHead(name, prefix.Length()) == prefix)), + AddRemoveTimerMarker{}, name, aTimer->mDelay.ToMilliseconds(), + MarkerThreadId::CurrentThread()); + // This adds a marker with the timer name as the marker name, to make it + // obvious which timers are being used. This marker will be useful to + // understand which timers might be added and removed excessively often. + profiler_add_marker(name, geckoprofiler::category::TIMER, + MarkerOptions(MarkerTiming::IntervalUntilNowFrom( + aTimer->mTimeout - aTimer->mDelay), + MarkerThreadId(mProfilerThreadId)), + TimerMarker{}, aTimer->mDelay.ToMilliseconds(), + aTimer->mType, MarkerThreadId::CurrentThread(), true); + } + + return NS_OK; +} + +TimeStamp TimerThread::FindNextFireTimeForCurrentThread(TimeStamp aDefault, + uint32_t aSearchBound) { + MonitorAutoLock lock(mMonitor); + AUTO_TIMERS_STATS(TimerThread_FindNextFireTimeForCurrentThread); + + for (const Entry& entry : mTimers) { + const nsTimerImpl* timer = entry.Value(); + if (timer) { + if (entry.Timeout() > aDefault) { + return aDefault; + } + + // Don't yield to timers created with the *_LOW_PRIORITY type. + if (!timer->IsLowPriority()) { + bool isOnCurrentThread = false; + nsresult rv = + timer->mEventTarget->IsOnCurrentThread(&isOnCurrentThread); + if (NS_SUCCEEDED(rv) && isOnCurrentThread) { + return entry.Timeout(); + } + } + + if (aSearchBound == 0) { + // Couldn't find any non-low priority timers for the current thread. + // Return a compromise between a very short and a long idle time. + TimeStamp fallbackDeadline = + TimeStamp::Now() + TimeDuration::FromMilliseconds(16); + return fallbackDeadline < aDefault ? fallbackDeadline : aDefault; + } + + --aSearchBound; + } + } + + // No timers for this thread, return the default. + return aDefault; +} + +// This function must be called from within a lock +// Also: we hold the mutex for the nsTimerImpl. +bool TimerThread::AddTimerInternal(nsTimerImpl& aTimer) { + mMonitor.AssertCurrentThreadOwns(); + aTimer.mMutex.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_AddTimerInternal); + if (mShutdown) { + return false; + } + + LogTimerEvent::LogDispatch(&aTimer); + + const TimeStamp& timeout = aTimer.mTimeout; + const size_t insertionIndex = ComputeTimerInsertionIndex(timeout); + + if (insertionIndex != 0 && !mTimers[insertionIndex - 1].Value()) { + // Very common scenario in practice: The timer just before the insertion + // point is canceled, overwrite it. + AUTO_TIMERS_STATS(TimerThread_AddTimerInternal_overwrite_before); + mTimers[insertionIndex - 1] = Entry{aTimer}; + return true; + } + + const size_t length = mTimers.Length(); + if (insertionIndex == length) { + // We're at the end (including it's the very first insertion), add new timer + // at the end. + AUTO_TIMERS_STATS(TimerThread_AddTimerInternal_append); + return mTimers.AppendElement(Entry{aTimer}, mozilla::fallible); + } + + if (!mTimers[insertionIndex].Value()) { + // The timer at the insertion point is canceled, overwrite it. + AUTO_TIMERS_STATS(TimerThread_AddTimerInternal_overwrite); + mTimers[insertionIndex] = Entry{aTimer}; + return true; + } + + // The new timer has to be inserted. + AUTO_TIMERS_STATS(TimerThread_AddTimerInternal_insert); + // The capacity should be checked first, because if it needs to be increased + // and the memory allocation fails, only the new timer should be lost. + if (length == mTimers.Capacity() && mTimers[length - 1].Value()) { + // We have reached capacity, and the last entry is not canceled, so we + // really want to increase the capacity in case the extra slot is required. + // To force-expand the array, append a canceled-timer entry with a timestamp + // far in the future. + // This empty Entry may be used below to receive the moved-from previous + // entry. If not, it may be used in a later call if we need to append a new + // timer at the end. + AUTO_TIMERS_STATS(TimerThread_AddTimerInternal_insert_expand); + if (!mTimers.AppendElement( + Entry{mTimers[length - 1].Timeout() + + TimeDuration::FromSeconds(365.0 * 24.0 * 60.0 * 60.0)}, + mozilla::fallible)) { + return false; + } + } + + // Extract the timer at the insertion point, and put the new timer in its + // place. + Entry extractedEntry = std::exchange(mTimers[insertionIndex], Entry{aTimer}); + // Following entries can be pushed until we hit a canceled timer or the end. + for (size_t i = insertionIndex + 1; i < length; ++i) { + Entry& entryRef = mTimers[i]; + if (!entryRef.Value()) { + // Canceled entry, overwrite it with the extracted entry from before. + COUNT_TIMERS_STATS(TimerThread_AddTimerInternal_insert_overwrite); + entryRef = std::move(extractedEntry); + return true; + } + // Write extracted entry from before, and extract current entry. + COUNT_TIMERS_STATS(TimerThread_AddTimerInternal_insert_shifts); + std::swap(entryRef, extractedEntry); + } + // We've reached the end of the list, with still one extracted entry to + // re-insert. We've checked the capacity above, this cannot fail. + COUNT_TIMERS_STATS(TimerThread_AddTimerInternal_insert_append); + mTimers.AppendElement(std::move(extractedEntry)); + return true; +} + +// This function must be called from within a lock +// Also: we hold the mutex for the nsTimerImpl. +bool TimerThread::RemoveTimerInternal(nsTimerImpl& aTimer) { + mMonitor.AssertCurrentThreadOwns(); + aTimer.mMutex.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_RemoveTimerInternal); + if (!aTimer.IsInTimerThread()) { + COUNT_TIMERS_STATS(TimerThread_RemoveTimerInternal_not_in_list); + return false; + } + AUTO_TIMERS_STATS(TimerThread_RemoveTimerInternal_in_list); + for (auto& entry : mTimers) { + if (entry.Value() == &aTimer) { + entry.Forget(); + return true; + } + } + MOZ_ASSERT(!aTimer.IsInTimerThread(), + "Not found in the list but it should be!?"); + return false; +} + +void TimerThread::RemoveLeadingCanceledTimersInternal() { + mMonitor.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_RemoveLeadingCanceledTimersInternal); + + size_t toRemove = 0; + while (toRemove < mTimers.Length() && !mTimers[toRemove].Value()) { + ++toRemove; + } + mTimers.RemoveElementsAt(0, toRemove); +} + +void TimerThread::RemoveFirstTimerInternal() { + mMonitor.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_RemoveFirstTimerInternal); + MOZ_ASSERT(!mTimers.IsEmpty()); + mTimers.RemoveElementAt(0); +} + +void TimerThread::PostTimerEvent(already_AddRefed aTimerRef) { + mMonitor.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_PostTimerEvent); + + RefPtr timer(aTimerRef); + +#if TIMER_THREAD_STATISTICS + const double actualFiringDelay = + std::max((TimeStamp::Now() - timer->mTimeout).ToMilliseconds(), 0.0); + if (mNotified) { + ++mTotalTimersFiredNotified; + mTotalActualTimerFiringDelayNotified += actualFiringDelay; + } else { + ++mTotalTimersFiredUnnotified; + mTotalActualTimerFiringDelayUnnotified += actualFiringDelay; + } +#endif + + if (!timer->mEventTarget) { + NS_ERROR("Attempt to post timer event to NULL event target"); + return; + } + + // 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. + + nsCOMPtr target = timer->mEventTarget; + + void* p = nsTimerEvent::operator new(sizeof(nsTimerEvent)); + if (!p) { + return; + } + RefPtr event = + ::new (KnownNotNull, p) nsTimerEvent(timer.forget(), mProfilerThreadId); + + nsresult rv; + { + // We release mMonitor around the Dispatch because if the Dispatch interacts + // with the timer API we'll deadlock. + MonitorAutoUnlock unlock(mMonitor); + rv = target->Dispatch(event, NS_DISPATCH_NORMAL); + if (NS_FAILED(rv)) { + timer = event->ForgetTimer(); + // We do this to avoid possible deadlock by taking the two locks in a + // different order than is used in RemoveTimer(). RemoveTimer() has + // aTimer->mMutex first. We use timer.get() to keep static analysis + // happy + // NOTE: I'm not sure that any of the below is actually necessary. It + // seems to me that the timer that we're trying to fire will have already + // been removed prior to this. + MutexAutoLock lock1(timer.get()->mMutex); + MonitorAutoLock lock2(mMonitor); + RemoveTimerInternal(*timer); + } + } +} + +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; + PROFILER_MARKER_UNTYPED("AfterSleep", OTHER, + MarkerThreadId(mProfilerThreadId)); + mMonitor.Notify(); +} + +NS_IMETHODIMP +TimerThread::Observe(nsISupports* aSubject, const char* aTopic, + const char16_t* aData) { + if (strcmp(aTopic, "ipc:process-priority-changed") == 0) { + nsCOMPtr props = do_QueryInterface(aSubject); + MOZ_ASSERT(props != nullptr); + + int32_t priority = static_cast(hal::PROCESS_PRIORITY_UNKNOWN); + props->GetPropertyAsInt32(u"priority"_ns, &priority); + mCachedPriority.store(static_cast(priority), + std::memory_order_relaxed); + } + + if (StaticPrefs::timer_ignore_sleep_wake_notifications()) { + return NS_OK; + } + + 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; +} + +uint32_t TimerThread::AllowedEarlyFiringMicroseconds() { + MonitorAutoLock lock(mMonitor); + return mAllowedEarlyFiringMicroseconds; +} + +#if TIMER_THREAD_STATISTICS +void TimerThread::PrintStatistics() const { + mMonitor.AssertCurrentThreadOwns(); + + const TimeStamp freshNow = TimeStamp::Now(); + const double timeElapsed = mFirstTimerAdded.IsNull() + ? 0.0 + : (freshNow - mFirstTimerAdded).ToSeconds(); + printf_stderr("TimerThread Stats (Total time %8.2fs)\n", timeElapsed); + + printf_stderr("Added: %6llu Removed: %6llu Fired: %6llu\n", mTotalTimersAdded, + mTotalTimersRemoved, + mTotalTimersFiredNotified + mTotalTimersFiredUnnotified); + + auto PrintTimersFiredBucket = + [](const AutoTArray& buckets, + const size_t wakeupCount, const size_t timersFiredCount, + const double totalTimerDelay, const char* label) { + printf_stderr("%s : [", label); + for (size_t bucketVal : buckets) { + printf_stderr(" %5llu", bucketVal); + } + printf_stderr( + " ] Wake-ups/timer %6llu / %6llu (%7.4f) Avg Timer Delay %7.4f\n", + wakeupCount, timersFiredCount, + static_cast(wakeupCount) / timersFiredCount, + totalTimerDelay / timersFiredCount); + }; + + printf_stderr("Wake-ups:\n"); + PrintTimersFiredBucket( + mTimersFiredPerWakeup, mTotalWakeupCount, + mTotalTimersFiredNotified + mTotalTimersFiredUnnotified, + mTotalActualTimerFiringDelayNotified + + mTotalActualTimerFiringDelayUnnotified, + "Total "); + PrintTimersFiredBucket(mTimersFiredPerNotifiedWakeup, + mTotalNotifiedWakeupCount, mTotalTimersFiredNotified, + mTotalActualTimerFiringDelayNotified, "Notified "); + PrintTimersFiredBucket(mTimersFiredPerUnnotifiedWakeup, + mTotalUnnotifiedWakeupCount, + mTotalTimersFiredUnnotified, + mTotalActualTimerFiringDelayUnnotified, "Unnotified "); + + printf_stderr("Early Wake-ups: %6llu Avg: %7.4fms\n", mEarlyWakeups, + mTotalEarlyWakeupTime / mEarlyWakeups); +} +#endif + +/* This nsReadOnlyTimer class is used for the values returned by the + * TimerThread::GetTimers method. + * It is not possible to return a strong reference to the nsTimerImpl + * instance (that could extend the lifetime of the timer and cause it to fire + * a callback pointing to already freed memory) or a weak reference + * (nsSupportsWeakReference doesn't support freeing the referee on a thread + * that isn't the thread that owns the weak reference), so instead the timer + * name, delay and type are copied to a new object. */ +class nsReadOnlyTimer final : public nsITimer { + public: + explicit nsReadOnlyTimer(const nsACString& aName, uint32_t aDelay, + uint32_t aType) + : mName(aName), mDelay(aDelay), mType(aType) {} + NS_DECL_ISUPPORTS + + NS_IMETHOD Init(nsIObserver* aObserver, uint32_t aDelayInMs, + uint32_t aType) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD InitWithCallback(nsITimerCallback* aCallback, uint32_t aDelayInMs, + uint32_t aType) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD InitHighResolutionWithCallback(nsITimerCallback* aCallback, + const mozilla::TimeDuration& aDelay, + uint32_t aType) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD Cancel(void) override { return NS_ERROR_NOT_IMPLEMENTED; } + NS_IMETHOD InitWithNamedFuncCallback(nsTimerCallbackFunc aCallback, + void* aClosure, uint32_t aDelay, + uint32_t aType, + const char* aName) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD InitHighResolutionWithNamedFuncCallback( + nsTimerCallbackFunc aCallback, void* aClosure, + const mozilla::TimeDuration& aDelay, uint32_t aType, + const char* aName) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + + NS_IMETHOD GetName(nsACString& aName) override { + aName = mName; + return NS_OK; + } + NS_IMETHOD GetDelay(uint32_t* aDelay) override { + *aDelay = mDelay; + return NS_OK; + } + NS_IMETHOD SetDelay(uint32_t aDelay) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD GetType(uint32_t* aType) override { + *aType = mType; + return NS_OK; + } + NS_IMETHOD SetType(uint32_t aType) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD GetClosure(void** aClosure) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD GetCallback(nsITimerCallback** aCallback) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD GetTarget(nsIEventTarget** aTarget) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD SetTarget(nsIEventTarget* aTarget) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + NS_IMETHOD GetAllowedEarlyFiringMicroseconds( + uint32_t* aAllowedEarlyFiringMicroseconds) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) override { + return sizeof(*this); + } + + private: + nsCString mName; + uint32_t mDelay; + uint32_t mType; + ~nsReadOnlyTimer() = default; +}; + +NS_IMPL_ISUPPORTS(nsReadOnlyTimer, nsITimer) + +nsresult TimerThread::GetTimers(nsTArray>& aRetVal) { + nsTArray> timers; + { + MonitorAutoLock lock(mMonitor); + for (const auto& entry : mTimers) { + nsTimerImpl* timer = entry.Value(); + if (!timer) { + continue; + } + timers.AppendElement(timer); + } + } + + for (nsTimerImpl* timer : timers) { + nsAutoCString name; + timer->GetName(name); + + uint32_t delay; + timer->GetDelay(&delay); + + uint32_t type; + timer->GetType(&type); + + aRetVal.AppendElement(new nsReadOnlyTimer(name, delay, type)); + } + + return NS_OK; +} -- cgit v1.2.3