diff options
Diffstat (limited to 'xpcom/threads/TimerThread.cpp')
| -rw-r--r-- | xpcom/threads/TimerThread.cpp | 961 |
1 files changed, 961 insertions, 0 deletions
diff --git a/xpcom/threads/TimerThread.cpp b/xpcom/threads/TimerThread.cpp new file mode 100644 index 0000000000..7e7c31b730 --- /dev/null +++ b/xpcom/threads/TimerThread.cpp @@ -0,0 +1,961 @@ +/* -*- 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 "pratom.h" + +#include "nsIObserverService.h" +#include "mozilla/Services.h" +#include "mozilla/ChaosMode.h" +#include "mozilla/ArenaAllocator.h" +#include "mozilla/ArrayUtils.h" +#include "mozilla/BinarySearch.h" +#include "mozilla/OperatorNewExtensions.h" +#include "mozilla/StaticPrefs_timer.h" + +#include <math.h> + +using namespace mozilla; + +// 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<ULL>(mCount); + if (n == 0) { + printf("[%d] Timers stats `%s`: (nothing)\n", + int(profiler_current_process_id().ToNumber()), mName); + } else if (ULL sumNs = static_cast<ULL>(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<ULL>(mLongestDurationNs)); + } + } + + void AddDurationFrom(TimeStamp aStart) { + // Duration between aStart and now, rounded to the nearest nanosecond. + DurationNs duration = static_cast<DurationNs>( + (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<DurationNs> mSumDurationsNs{0}; + Atomic<DurationNs> mLongestDurationNs{0}; + Atomic<Count> 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"); +} + +namespace { + +class TimerObserverRunnable : public Runnable { + public: + explicit TimerObserverRunnable(nsIObserver* aObserver) + : mozilla::Runnable("TimerObserverRunnable"), 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 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() + : mPool(), 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<nsTimerImpl> 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<nsTimerImpl> 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<nsTimerImpl> mTimer; + const int32_t mGeneration; + ProfilerThreadId mTimerThreadId; + + static TimerEventAllocator* sAllocator; + + static Atomic<int32_t, SequentiallyConsistent> sAllocatorUsers; + static Atomic<bool, SequentiallyConsistent> sCanDeleteAllocator; +}; + +TimerEventAllocator* nsTimerEvent::sAllocator = nullptr; +Atomic<int32_t, SequentiallyConsistent> nsTimerEvent::sAllocatorUsers; +Atomic<bool, SequentiallyConsistent> 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<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; + } +} + +#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)) { + nsAutoCString name; + mTimer->GetName(name); + PROFILER_MARKER_TEXT( + "PostTimerEvent", OTHER, + MarkerOptions(MOZ_LIKELY(mInitTime) + ? MarkerTiming::IntervalUntilNowFrom(mInitTime) + : MarkerTiming::InstantNow(), + MarkerThreadId(mTimerThreadId)), + name); + } + + 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<TimerObserverRunnable> 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<RefPtr<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. + for (const UniquePtr<Entry>& entry : mTimers) { + timers.AppendElement(entry->Take()); + } + + mTimers.Clear(); + } + + for (const RefPtr<nsTimerImpl>& timer : timers) { + if (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 + +NS_IMETHODIMP +TimerThread::Run() { + MonitorAutoLock lock(mMonitor); + + mProfilerThreadId = profiler_current_thread_id(); + + // 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 + mAllowedEarlyFiringMicroseconds = usIntervalResolution / 2; + bool forceRunNextTimer = false; + + while (!mShutdown) { + // Have to use PRIntervalTime here, since PR_WaitCondVar takes it + TimeDuration 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 = TimeDuration::FromMilliseconds(milliseconds); + } else { + waitFor = TimeDuration::Forever(); + TimeStamp now = TimeStamp::Now(); + + RemoveLeadingCanceledTimersInternal(); + + if (!mTimers.IsEmpty()) { + if (now >= 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<nsTimerImpl> 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. + { + 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(); + + 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 < mAllowedEarlyFiringMicroseconds) { + forceRunNextTimer = false; + goto next; // round down; execute event now + } + waitFor = TimeDuration::FromMicroseconds(microseconds); + if (waitFor.IsZero()) { + // round up, wait the minimum time we can wait + waitFor = TimeDuration::FromMicroseconds(1); + } + } + + 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())); + } + } + + mWaiting = true; + mNotified = false; + { + AUTO_PROFILER_TRACING_MARKER("TimerThread", "Wait", OTHER); + mMonitor.Wait(waitFor); + } + if (mNotified) { + forceRunNextTimer = false; + } + mWaiting = false; + } + + 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; + } + + // Add the timer to our list. + if (!AddTimerInternal(aTimer)) { + return NS_ERROR_OUT_OF_MEMORY; + } + + // Awaken the timer thread if: + // - This is the new front timer, which may require the TimerThread to wake up + // earlier than previously planned. 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! + if (mWaiting && (mTimers[0]->Value() == aTimer || aTimer->mDelay.IsZero())) { + mNotified = true; + mMonitor.Notify(); + } + + if (profiler_thread_is_being_profiled_for_markers(mProfilerThreadId)) { + struct TimerMarker { + static constexpr Span<const char> MarkerTypeName() { + return MakeStringSpan("Timer"); + } + 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<int64_t>( + 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; + } + }; + + nsAutoCString name; + aTimer->GetName(name, aProofOfLock); + + nsLiteralCString prefix("Anonymous_"); + profiler_add_marker( + "AddTimer", geckoprofiler::category::OTHER, + MarkerOptions(MarkerThreadId(mProfilerThreadId), + MarkerStack::MaybeCapture( + StringHead(name, prefix.Length()) == prefix)), + TimerMarker{}, 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; + } + + // 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_"); + PROFILER_MARKER_TEXT( + "RemoveTimer", OTHER, + MarkerOptions(MarkerThreadId(mProfilerThreadId), + MarkerStack::MaybeCapture( + StringHead(name, prefix.Length()) == prefix)), + name); + } + + return NS_OK; +} + +TimeStamp TimerThread::FindNextFireTimeForCurrentThread(TimeStamp aDefault, + uint32_t aSearchBound) { + MonitorAutoLock lock(mMonitor); + AUTO_TIMERS_STATS(TimerThread_FindNextFireTimeForCurrentThread); + TimeStamp timeStamp = aDefault; + uint32_t index = 0; + +#ifdef DEBUG + TimeStamp firstTimeStamp; + Entry* initialFirstEntry = nullptr; + if (!mTimers.IsEmpty()) { + initialFirstEntry = mTimers[0].get(); + firstTimeStamp = mTimers[0]->Timeout(); + } +#endif + + auto end = mTimers.end(); + while (end != mTimers.begin()) { + nsTimerImpl* timer = mTimers[0]->Value(); + if (timer) { + if (timer->mTimeout > aDefault) { + timeStamp = aDefault; + break; + } + + // 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) { + timeStamp = timer->mTimeout; + break; + } + } + + if (++index > aSearchBound) { + // Track the currently highest timeout so that we can bail out when we + // reach the bound or when we find a timer for the current thread. + // This won't give accurate information if we stop before finding + // any timer for the current thread, but at least won't report too + // long idle period. + timeStamp = timer->mTimeout; + break; + } + } + + std::pop_heap(mTimers.begin(), end, Entry::UniquePtrLessThan); + --end; + } + + while (end != mTimers.end()) { + ++end; + std::push_heap(mTimers.begin(), end, Entry::UniquePtrLessThan); + } + +#ifdef DEBUG + if (!mTimers.IsEmpty()) { + if (firstTimeStamp != mTimers[0]->Timeout()) { + TimeStamp now = TimeStamp::Now(); + printf_stderr( + "firstTimeStamp %f, mTimers[0]->Timeout() %f, " + "initialFirstTimer %p, current first %p\n", + (firstTimeStamp - now).ToMilliseconds(), + (mTimers[0]->Timeout() - now).ToMilliseconds(), initialFirstEntry, + mTimers[0].get()); + } + } + MOZ_ASSERT_IF(!mTimers.IsEmpty(), firstTimeStamp == mTimers[0]->Timeout()); +#endif + + return timeStamp; +} + +// 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; + } + + TimeStamp now = TimeStamp::Now(); + + LogTimerEvent::LogDispatch(aTimer); + + UniquePtr<Entry>* entry = mTimers.AppendElement( + MakeUnique<Entry>(now, aTimer->mTimeout, aTimer), mozilla::fallible); + if (!entry) { + return false; + } + + std::push_heap(mTimers.begin(), mTimers.end(), Entry::UniquePtrLessThan); + + 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) { + COUNT_TIMERS_STATS(TimerThread_RemoveTimerInternal_nullptr); + return false; + } + if (!aTimer->mHolder) { + COUNT_TIMERS_STATS(TimerThread_RemoveTimerInternal_not_in_list); + return false; + } + AUTO_TIMERS_STATS(TimerThread_RemoveTimerInternal_in_list); + aTimer->mHolder->Forget(aTimer); + return true; +} + +void TimerThread::RemoveLeadingCanceledTimersInternal() { + mMonitor.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_RemoveLeadingCanceledTimersInternal); + + // Move all canceled timers from the front of the list to + // the back of the list using std::pop_heap(). We do this + // without actually removing them from the list so we can + // modify the nsTArray in a single bulk operation. + auto sortedEnd = mTimers.end(); + while (sortedEnd != mTimers.begin() && !mTimers[0]->Value()) { + std::pop_heap(mTimers.begin(), sortedEnd, Entry::UniquePtrLessThan); + --sortedEnd; + } + + // If there were no canceled timers then we are done. + if (sortedEnd == mTimers.end()) { + return; + } + + // Finally, remove the canceled timers from the back of the + // nsTArray. + mTimers.RemoveLastElements(mTimers.end() - sortedEnd); +} + +void TimerThread::RemoveFirstTimerInternal() { + mMonitor.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_RemoveFirstTimerInternal); + MOZ_ASSERT(!mTimers.IsEmpty()); + std::pop_heap(mTimers.begin(), mTimers.end(), Entry::UniquePtrLessThan); + mTimers.RemoveLastElement(); +} + +void TimerThread::PostTimerEvent(already_AddRefed<nsTimerImpl> aTimerRef) { + mMonitor.AssertCurrentThreadOwns(); + AUTO_TIMERS_STATS(TimerThread_PostTimerEvent); + + RefPtr<nsTimerImpl> timer(aTimerRef); + 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<nsIEventTarget> target = timer->mEventTarget; + + void* p = nsTimerEvent::operator new(sizeof(nsTimerEvent)); + if (!p) { + return; + } + RefPtr<nsTimerEvent> 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 + MutexAutoLock lock1(timer.get()->mMutex); + MonitorAutoLock lock2(mMonitor); + RemoveTimerInternal(timer.get()); + } + } +} + +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 (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; +} |