Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 804 insertions, 0 deletions

diff --git a/xpcom/threads/nsTimerImpl.cpp b/xpcom/threads/nsTimerImpl.cpp
new file mode 100644
index 0000000000..5e9061c9bd
--- /dev/null
+++ b/xpcom/threads/nsTimerImpl.cpp
@@ -0,0 +1,804 @@
+/* -*- 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 <utility>
+
+#include "GeckoProfiler.h"
+#include "TimerThread.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/Sprintf.h"
+#include "nsThreadManager.h"
+#include "nsThreadUtils.h"
+#include "pratom.h"
+#ifdef MOZ_TASK_TRACER
+#  include "GeckoTaskTracerImpl.h"
+using namespace mozilla::tasktracer;
+#endif
+
+#ifdef XP_WIN
+#  include <process.h>
+#  ifndef getpid
+#    define getpid _getpid
+#  endif
+#else
+#  include <unistd.h>
+#endif
+
+using mozilla::Atomic;
+using mozilla::LogLevel;
+using mozilla::MakeRefPtr;
+using mozilla::MutexAutoLock;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+
+static TimerThread* gThread = nullptr;
+
+// This module prints info about the precision of timers.
+static mozilla::LazyLogModule sTimerLog("nsTimerImpl");
+
+mozilla::LogModule* GetTimerLog() { return sTimerLog; }
+
+TimeStamp NS_GetTimerDeadlineHintOnCurrentThread(TimeStamp aDefault,
+                                                 uint32_t aSearchBound) {
+  return gThread
+             ? gThread->FindNextFireTimeForCurrentThread(aDefault, aSearchBound)
+             : TimeStamp();
+}
+
+already_AddRefed<nsITimer> NS_NewTimer() { return NS_NewTimer(nullptr); }
+
+already_AddRefed<nsITimer> NS_NewTimer(nsIEventTarget* aTarget) {
+  return nsTimer::WithEventTarget(aTarget).forget();
+}
+
+mozilla::Result<nsCOMPtr<nsITimer>, nsresult> NS_NewTimerWithObserver(
+    nsIObserver* aObserver, uint32_t aDelay, uint32_t aType,
+    nsIEventTarget* aTarget) {
+  nsCOMPtr<nsITimer> timer;
+  MOZ_TRY(NS_NewTimerWithObserver(getter_AddRefs(timer), aObserver, aDelay,
+                                  aType, aTarget));
+  return std::move(timer);
+}
+nsresult NS_NewTimerWithObserver(nsITimer** aTimer, nsIObserver* aObserver,
+                                 uint32_t aDelay, uint32_t aType,
+                                 nsIEventTarget* aTarget) {
+  auto timer = nsTimer::WithEventTarget(aTarget);
+
+  MOZ_TRY(timer->Init(aObserver, aDelay, aType));
+  timer.forget(aTimer);
+  return NS_OK;
+}
+
+mozilla::Result<nsCOMPtr<nsITimer>, nsresult> NS_NewTimerWithCallback(
+    nsITimerCallback* aCallback, uint32_t aDelay, uint32_t aType,
+    nsIEventTarget* aTarget) {
+  nsCOMPtr<nsITimer> timer;
+  MOZ_TRY(NS_NewTimerWithCallback(getter_AddRefs(timer), aCallback, aDelay,
+                                  aType, aTarget));
+  return std::move(timer);
+}
+nsresult NS_NewTimerWithCallback(nsITimer** aTimer, nsITimerCallback* aCallback,
+                                 uint32_t aDelay, uint32_t aType,
+                                 nsIEventTarget* aTarget) {
+  auto timer = nsTimer::WithEventTarget(aTarget);
+
+  MOZ_TRY(timer->InitWithCallback(aCallback, aDelay, aType));
+  timer.forget(aTimer);
+  return NS_OK;
+}
+
+mozilla::Result<nsCOMPtr<nsITimer>, nsresult> NS_NewTimerWithCallback(
+    nsITimerCallback* aCallback, const TimeDuration& aDelay, uint32_t aType,
+    nsIEventTarget* aTarget) {
+  nsCOMPtr<nsITimer> timer;
+  MOZ_TRY(NS_NewTimerWithCallback(getter_AddRefs(timer), aCallback, aDelay,
+                                  aType, aTarget));
+  return std::move(timer);
+}
+nsresult NS_NewTimerWithCallback(nsITimer** aTimer, nsITimerCallback* aCallback,
+                                 const TimeDuration& aDelay, uint32_t aType,
+                                 nsIEventTarget* aTarget) {
+  auto timer = nsTimer::WithEventTarget(aTarget);
+
+  MOZ_TRY(timer->InitHighResolutionWithCallback(aCallback, aDelay, aType));
+  timer.forget(aTimer);
+  return NS_OK;
+}
+
+mozilla::Result<nsCOMPtr<nsITimer>, nsresult> NS_NewTimerWithFuncCallback(
+    nsTimerCallbackFunc aCallback, void* aClosure, uint32_t aDelay,
+    uint32_t aType, const char* aNameString, nsIEventTarget* aTarget) {
+  nsCOMPtr<nsITimer> timer;
+  MOZ_TRY(NS_NewTimerWithFuncCallback(getter_AddRefs(timer), aCallback,
+                                      aClosure, aDelay, aType, aNameString,
+                                      aTarget));
+  return std::move(timer);
+}
+nsresult NS_NewTimerWithFuncCallback(nsITimer** aTimer,
+                                     nsTimerCallbackFunc aCallback,
+                                     void* aClosure, uint32_t aDelay,
+                                     uint32_t aType, const char* aNameString,
+                                     nsIEventTarget* aTarget) {
+  auto timer = nsTimer::WithEventTarget(aTarget);
+
+  MOZ_TRY(timer->InitWithNamedFuncCallback(aCallback, aClosure, aDelay, aType,
+                                           aNameString));
+  timer.forget(aTimer);
+  return NS_OK;
+}
+
+mozilla::Result<nsCOMPtr<nsITimer>, nsresult> NS_NewTimerWithFuncCallback(
+    nsTimerCallbackFunc aCallback, void* aClosure, uint32_t aDelay,
+    uint32_t aType, nsTimerNameCallbackFunc aNameCallback,
+    nsIEventTarget* aTarget) {
+  nsCOMPtr<nsITimer> timer;
+  MOZ_TRY(NS_NewTimerWithFuncCallback(getter_AddRefs(timer), aCallback,
+                                      aClosure, aDelay, aType, aNameCallback,
+                                      aTarget));
+  return std::move(timer);
+}
+nsresult NS_NewTimerWithFuncCallback(nsITimer** aTimer,
+                                     nsTimerCallbackFunc aCallback,
+                                     void* aClosure, uint32_t aDelay,
+                                     uint32_t aType,
+                                     nsTimerNameCallbackFunc aNameCallback,
+                                     nsIEventTarget* aTarget) {
+  auto timer = nsTimer::WithEventTarget(aTarget);
+
+  MOZ_TRY(timer->InitWithNameableFuncCallback(aCallback, aClosure, aDelay,
+                                              aType, aNameCallback));
+  timer.forget(aTimer);
+  return NS_OK;
+}
+
+// This module prints info about which timers are firing, which is useful for
+// wakeups for the purposes of power profiling. Set the following environment
+// variable before starting the browser.
+//
+//   MOZ_LOG=TimerFirings:4
+//
+// Then a line will be printed for every timer that fires. The name used for a
+// |Callback::Type::Function| timer depends on the circumstances.
+//
+// - If it was explicitly named (e.g. it was initialized with
+//   InitWithNamedFuncCallback()) then that explicit name will be shown.
+//
+// - Otherwise, if we are on a platform that supports function name lookup
+//   (Mac or Linux) then the looked-up name will be shown with a
+//   "[from dladdr]" annotation. On Mac the looked-up name will be immediately
+//   useful. On Linux it'll need post-processing with `tools/rb/fix_stacks.py`.
+//
+// - Otherwise, no name will be printed. If many timers hit this case then
+//   you'll need to re-run the workload on a Mac to find out which timers they
+//   are, and then give them explicit names.
+//
+// If you redirect this output to a file called "out", you can then
+// post-process it with a command something like the following.
+//
+//   cat out | grep timer | sort | uniq -c | sort -r -n
+//
+// This will show how often each unique line appears, with the most common ones
+// first.
+//
+// More detailed docs are here:
+// https://developer.mozilla.org/en-US/docs/Mozilla/Performance/TimerFirings_logging
+//
+static mozilla::LazyLogModule sTimerFiringsLog("TimerFirings");
+
+static mozilla::LogModule* GetTimerFiringsLog() { return sTimerFiringsLog; }
+
+#include <math.h>
+
+double nsTimerImpl::sDeltaSumSquared = 0;
+double nsTimerImpl::sDeltaSum = 0;
+double nsTimerImpl::sDeltaNum = 0;
+
+static void myNS_MeanAndStdDev(double n, double sumOfValues,
+                               double sumOfSquaredValues, double* meanResult,
+                               double* stdDevResult) {
+  double mean = 0.0, var = 0.0, stdDev = 0.0;
+  if (n > 0.0 && sumOfValues >= 0) {
+    mean = sumOfValues / n;
+    double temp = (n * sumOfSquaredValues) - (sumOfValues * sumOfValues);
+    if (temp < 0.0 || n <= 1) {
+      var = 0.0;
+    } else {
+      var = temp / (n * (n - 1));
+    }
+    // for some reason, Windows says sqrt(0.0) is "-1.#J" (?!) so do this:
+    stdDev = var != 0.0 ? sqrt(var) : 0.0;
+  }
+  *meanResult = mean;
+  *stdDevResult = stdDev;
+}
+
+NS_IMPL_QUERY_INTERFACE(nsTimer, nsITimer)
+NS_IMPL_ADDREF(nsTimer)
+
+NS_IMETHODIMP_(MozExternalRefCountType)
+nsTimer::Release(void) {
+  nsrefcnt count = --mRefCnt;
+  NS_LOG_RELEASE(this, count, "nsTimer");
+
+  if (count == 1) {
+    // Last ref, in nsTimerImpl::mITimer. Make sure the cycle is broken.
+    mImpl->CancelImpl(true);
+  } else if (count == 0) {
+    delete this;
+  }
+
+  return count;
+}
+
+nsTimerImpl::nsTimerImpl(nsITimer* aTimer, nsIEventTarget* aTarget)
+    : mEventTarget(aTarget),
+      mHolder(nullptr),
+      mType(0),
+      mGeneration(0),
+      mITimer(aTimer),
+      mMutex("nsTimerImpl::mMutex"),
+      mFiring(0) {
+  // XXX some code creates timers during xpcom shutdown, when threads are no
+  // longer available, so we cannot turn this on yet.
+  // MOZ_ASSERT(mEventTarget);
+}
+
+// static
+nsresult nsTimerImpl::Startup() {
+  nsresult rv;
+
+  gThread = new TimerThread();
+
+  NS_ADDREF(gThread);
+  rv = gThread->InitLocks();
+
+  if (NS_FAILED(rv)) {
+    NS_RELEASE(gThread);
+  }
+
+  return rv;
+}
+
+void nsTimerImpl::Shutdown() {
+  if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug)) {
+    double mean = 0, stddev = 0;
+    myNS_MeanAndStdDev(sDeltaNum, sDeltaSum, sDeltaSumSquared, &mean, &stddev);
+
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+            ("sDeltaNum = %f, sDeltaSum = %f, sDeltaSumSquared = %f\n",
+             sDeltaNum, sDeltaSum, sDeltaSumSquared));
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+            ("mean: %fms, stddev: %fms\n", mean, stddev));
+  }
+
+  if (!gThread) {
+    return;
+  }
+
+  gThread->Shutdown();
+  NS_RELEASE(gThread);
+}
+
+nsresult nsTimerImpl::InitCommon(uint32_t aDelayMS, uint32_t aType,
+                                 Callback&& aNewCallback) {
+  return InitCommon(TimeDuration::FromMilliseconds(aDelayMS), aType,
+                    std::move(aNewCallback));
+}
+
+nsresult nsTimerImpl::InitCommon(const TimeDuration& aDelay, uint32_t aType,
+                                 Callback&& newCallback) {
+  mMutex.AssertCurrentThreadOwns();
+
+  if (!gThread) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  if (!mEventTarget) {
+    NS_ERROR("mEventTarget is NULL");
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  gThread->RemoveTimer(this);
+  mCallback.swap(newCallback);
+  ++mGeneration;
+
+  mType = (uint8_t)aType;
+  mDelay = aDelay;
+  mTimeout = TimeStamp::Now() + mDelay;
+
+  return gThread->AddTimer(this);
+}
+
+nsresult nsTimerImpl::InitWithFuncCallbackCommon(nsTimerCallbackFunc aFunc,
+                                                 void* aClosure,
+                                                 uint32_t aDelay,
+                                                 uint32_t aType,
+                                                 const Callback::Name& aName) {
+  if (NS_WARN_IF(!aFunc)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  Callback cb;  // Goes out of scope after the unlock, prevents deadlock
+  cb.mType = Callback::Type::Function;
+  cb.mCallback.c = aFunc;
+  cb.mClosure = aClosure;
+  cb.mName = aName;
+
+  MutexAutoLock lock(mMutex);
+  return InitCommon(aDelay, aType, std::move(cb));
+}
+
+nsresult nsTimerImpl::InitWithNamedFuncCallback(nsTimerCallbackFunc aFunc,
+                                                void* aClosure, uint32_t aDelay,
+                                                uint32_t aType,
+                                                const char* aNameString) {
+  Callback::Name name(aNameString);
+  return InitWithFuncCallbackCommon(aFunc, aClosure, aDelay, aType, name);
+}
+
+nsresult nsTimerImpl::InitWithNameableFuncCallback(
+    nsTimerCallbackFunc aFunc, void* aClosure, uint32_t aDelay, uint32_t aType,
+    nsTimerNameCallbackFunc aNameFunc) {
+  Callback::Name name(aNameFunc);
+  return InitWithFuncCallbackCommon(aFunc, aClosure, aDelay, aType, name);
+}
+
+nsresult nsTimerImpl::InitWithCallback(nsITimerCallback* aCallback,
+                                       uint32_t aDelayInMs, uint32_t aType) {
+  return InitHighResolutionWithCallback(
+      aCallback, TimeDuration::FromMilliseconds(aDelayInMs), aType);
+}
+
+nsresult nsTimerImpl::InitHighResolutionWithCallback(
+    nsITimerCallback* aCallback, const TimeDuration& aDelay, uint32_t aType) {
+  if (NS_WARN_IF(!aCallback)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  Callback cb;  // Goes out of scope after the unlock, prevents deadlock
+  cb.mType = Callback::Type::Interface;
+  cb.mCallback.i = aCallback;
+  NS_ADDREF(cb.mCallback.i);
+
+  MutexAutoLock lock(mMutex);
+  return InitCommon(aDelay, aType, std::move(cb));
+}
+
+nsresult nsTimerImpl::Init(nsIObserver* aObserver, uint32_t aDelayInMs,
+                           uint32_t aType) {
+  if (NS_WARN_IF(!aObserver)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  Callback cb;  // Goes out of scope after the unlock, prevents deadlock
+  cb.mType = Callback::Type::Observer;
+  cb.mCallback.o = aObserver;
+  NS_ADDREF(cb.mCallback.o);
+
+  MutexAutoLock lock(mMutex);
+  return InitCommon(aDelayInMs, aType, std::move(cb));
+}
+
+nsresult nsTimerImpl::Cancel() {
+  CancelImpl(false);
+  return NS_OK;
+}
+
+void nsTimerImpl::CancelImpl(bool aClearITimer) {
+  Callback cbTrash;
+  RefPtr<nsITimer> timerTrash;
+
+  {
+    MutexAutoLock lock(mMutex);
+    if (gThread) {
+      gThread->RemoveTimer(this);
+    }
+
+    cbTrash.swap(mCallback);
+    ++mGeneration;
+
+    // Don't clear this if we're firing; once Fire returns, we'll get this call
+    // again.
+    if (aClearITimer && !mFiring) {
+      MOZ_RELEASE_ASSERT(
+          mITimer,
+          "mITimer was nulled already! "
+          "This indicates that someone has messed up the refcount on nsTimer!");
+      timerTrash.swap(mITimer);
+    }
+  }
+}
+
+nsresult nsTimerImpl::SetDelay(uint32_t aDelay) {
+  MutexAutoLock lock(mMutex);
+  if (GetCallback().mType == Callback::Type::Unknown && !IsRepeating()) {
+    // This may happen if someone tries to re-use a one-shot timer
+    // by re-setting delay instead of reinitializing the timer.
+    NS_ERROR(
+        "nsITimer->SetDelay() called when the "
+        "one-shot timer is not set up.");
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  bool reAdd = false;
+  if (gThread) {
+    reAdd = NS_SUCCEEDED(gThread->RemoveTimer(this));
+  }
+
+  mDelay = TimeDuration::FromMilliseconds(aDelay);
+  mTimeout = TimeStamp::Now() + mDelay;
+
+  if (reAdd) {
+    gThread->AddTimer(this);
+  }
+
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::GetDelay(uint32_t* aDelay) {
+  MutexAutoLock lock(mMutex);
+  *aDelay = mDelay.ToMilliseconds();
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::SetType(uint32_t aType) {
+  MutexAutoLock lock(mMutex);
+  mType = (uint8_t)aType;
+  // XXX if this is called, we should change the actual type.. this could effect
+  // repeating timers.  we need to ensure in Fire() that if mType has changed
+  // during the callback that we don't end up with the timer in the queue twice.
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::GetType(uint32_t* aType) {
+  MutexAutoLock lock(mMutex);
+  *aType = mType;
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::GetClosure(void** aClosure) {
+  MutexAutoLock lock(mMutex);
+  *aClosure = GetCallback().mClosure;
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::GetCallback(nsITimerCallback** aCallback) {
+  MutexAutoLock lock(mMutex);
+  if (GetCallback().mType == Callback::Type::Interface) {
+    NS_IF_ADDREF(*aCallback = GetCallback().mCallback.i);
+  } else {
+    *aCallback = nullptr;
+  }
+
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::GetTarget(nsIEventTarget** aTarget) {
+  MutexAutoLock lock(mMutex);
+  NS_IF_ADDREF(*aTarget = mEventTarget);
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::SetTarget(nsIEventTarget* aTarget) {
+  MutexAutoLock lock(mMutex);
+  if (NS_WARN_IF(mCallback.mType != Callback::Type::Unknown)) {
+    return NS_ERROR_ALREADY_INITIALIZED;
+  }
+
+  if (aTarget) {
+    mEventTarget = aTarget;
+  } else {
+    mEventTarget = mozilla::GetCurrentSerialEventTarget();
+  }
+  return NS_OK;
+}
+
+nsresult nsTimerImpl::GetAllowedEarlyFiringMicroseconds(uint32_t* aValueOut) {
+  *aValueOut = gThread ? gThread->AllowedEarlyFiringMicroseconds() : 0;
+  return NS_OK;
+}
+
+void nsTimerImpl::Fire(int32_t aGeneration) {
+  uint8_t oldType;
+  uint32_t oldDelay;
+  TimeStamp oldTimeout;
+  Callback callbackDuringFire;
+  nsCOMPtr<nsITimer> kungFuDeathGrip;
+
+  {
+    // Don't fire callbacks or fiddle with refcounts when the mutex is locked.
+    // If some other thread Cancels/Inits after this, they're just too late.
+    MutexAutoLock lock(mMutex);
+    if (aGeneration != mGeneration) {
+      return;
+    }
+
+    ++mFiring;
+    callbackDuringFire = mCallback;
+    oldType = mType;
+    oldDelay = mDelay.ToMilliseconds();
+    oldTimeout = mTimeout;
+    // Ensure that the nsITimer does not unhook from the nsTimerImpl during
+    // Fire; this will cause null pointer crashes if the user of the timer drops
+    // its reference, and then uses the nsITimer* passed in the callback.
+    kungFuDeathGrip = mITimer;
+  }
+
+  AUTO_PROFILER_LABEL("nsTimerImpl::Fire", OTHER);
+
+  TimeStamp now = TimeStamp::Now();
+  if (MOZ_LOG_TEST(GetTimerLog(), LogLevel::Debug)) {
+    TimeDuration delta = now - oldTimeout;
+    int32_t d = delta.ToMilliseconds();  // delta in ms
+    sDeltaSum += abs(d);
+    sDeltaSumSquared += double(d) * double(d);
+    sDeltaNum++;
+
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+            ("[this=%p] expected delay time %4ums\n", this, oldDelay));
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+            ("[this=%p] actual delay time   %4dms\n", this, oldDelay + d));
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+            ("[this=%p] (mType is %d)       -------\n", this, oldType));
+    MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+            ("[this=%p]     delta           %4dms\n", this, d));
+  }
+
+  if (MOZ_LOG_TEST(GetTimerFiringsLog(), LogLevel::Debug)) {
+    LogFiring(callbackDuringFire, oldType, oldDelay);
+  }
+
+  switch (callbackDuringFire.mType) {
+    case Callback::Type::Function:
+      callbackDuringFire.mCallback.c(mITimer, callbackDuringFire.mClosure);
+      break;
+    case Callback::Type::Interface:
+      callbackDuringFire.mCallback.i->Notify(mITimer);
+      break;
+    case Callback::Type::Observer:
+      callbackDuringFire.mCallback.o->Observe(mITimer, NS_TIMER_CALLBACK_TOPIC,
+                                              nullptr);
+      break;
+    default:;
+  }
+
+  MutexAutoLock lock(mMutex);
+  if (aGeneration == mGeneration) {
+    if (IsRepeating()) {
+      // Repeating timer has not been re-init or canceled; reschedule
+      if (IsSlack()) {
+        mTimeout = TimeStamp::Now() + mDelay;
+      } else {
+        mTimeout = mTimeout + mDelay;
+      }
+      if (gThread) {
+        gThread->AddTimer(this);
+      }
+    } else {
+      // Non-repeating timer that has not been re-scheduled. Clear.
+      mCallback.clear();
+    }
+  }
+
+  --mFiring;
+
+  MOZ_LOG(GetTimerLog(), LogLevel::Debug,
+          ("[this=%p] Took %fms to fire timer callback\n", this,
+           (TimeStamp::Now() - now).ToMilliseconds()));
+}
+
+#if defined(HAVE_DLADDR) && defined(HAVE___CXA_DEMANGLE)
+#  define USE_DLADDR 1
+#endif
+
+#ifdef USE_DLADDR
+#  include <cxxabi.h>
+#  include <dlfcn.h>
+#endif
+
+// See the big comment above GetTimerFiringsLog() to understand this code.
+void nsTimerImpl::LogFiring(const Callback& aCallback, uint8_t aType,
+                            uint32_t aDelay) {
+  const char* typeStr;
+  switch (aType) {
+    case nsITimer::TYPE_ONE_SHOT:
+      typeStr = "ONE_SHOT  ";
+      break;
+    case nsITimer::TYPE_ONE_SHOT_LOW_PRIORITY:
+      typeStr = "ONE_LOW   ";
+      break;
+    case nsITimer::TYPE_REPEATING_SLACK:
+      typeStr = "SLACK     ";
+      break;
+    case nsITimer::TYPE_REPEATING_SLACK_LOW_PRIORITY:
+      typeStr = "SLACK_LOW ";
+      break;
+    case nsITimer::TYPE_REPEATING_PRECISE: /* fall through */
+    case nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP:
+      typeStr = "PRECISE   ";
+      break;
+    default:
+      MOZ_CRASH("bad type");
+  }
+
+  switch (aCallback.mType) {
+    case Callback::Type::Function: {
+      bool needToFreeName = false;
+      const char* annotation = "";
+      const char* name;
+      static const size_t buflen = 1024;
+      char buf[buflen];
+
+      if (aCallback.mName.is<Callback::NameString>()) {
+        name = aCallback.mName.as<Callback::NameString>();
+
+      } else if (aCallback.mName.is<Callback::NameFunc>()) {
+        aCallback.mName.as<Callback::NameFunc>()(
+            mITimer, /* aAnonymize = */ false, aCallback.mClosure, buf, buflen);
+        name = buf;
+
+      } else {
+        MOZ_ASSERT(aCallback.mName.is<Callback::NameNothing>());
+#ifdef USE_DLADDR
+        annotation = "[from dladdr] ";
+
+        Dl_info info;
+        void* addr = reinterpret_cast<void*>(aCallback.mCallback.c);
+        if (dladdr(addr, &info) == 0) {
+          name = "???[dladdr: failed]";
+
+        } else if (info.dli_sname) {
+          int status;
+          name = abi::__cxa_demangle(info.dli_sname, nullptr, nullptr, &status);
+          if (status == 0) {
+            // Success. Because we didn't pass in a buffer to __cxa_demangle it
+            // allocates its own one with malloc() which we must free() later.
+            MOZ_ASSERT(name);
+            needToFreeName = true;
+          } else if (status == -1) {
+            name = "???[__cxa_demangle: OOM]";
+          } else if (status == -2) {
+            name = "???[__cxa_demangle: invalid mangled name]";
+          } else if (status == -3) {
+            name = "???[__cxa_demangle: invalid argument]";
+          } else {
+            name = "???[__cxa_demangle: unexpected status value]";
+          }
+
+        } else if (info.dli_fname) {
+          // The "#0: " prefix is necessary for `fix_stacks.py` to interpret
+          // this string as something to convert.
+          SprintfLiteral(buf, "#0: ???[%s +0x%" PRIxPTR "]\n", info.dli_fname,
+                         uintptr_t(addr) - uintptr_t(info.dli_fbase));
+          name = buf;
+
+        } else {
+          name = "???[dladdr: no symbol or shared object obtained]";
+        }
+#else
+        name = "???[dladdr is unimplemented or doesn't work well on this OS]";
+#endif
+      }
+
+      MOZ_LOG(GetTimerFiringsLog(), LogLevel::Debug,
+              ("[%d]    fn timer (%s %5d ms): %s%s\n", getpid(), typeStr,
+               aDelay, annotation, name));
+
+      if (needToFreeName) {
+        free(const_cast<char*>(name));
+      }
+
+      break;
+    }
+
+    case Callback::Type::Interface: {
+      MOZ_LOG(GetTimerFiringsLog(), LogLevel::Debug,
+              ("[%d] iface timer (%s %5d ms): %p\n", getpid(), typeStr, aDelay,
+               aCallback.mCallback.i));
+      break;
+    }
+
+    case Callback::Type::Observer: {
+      MOZ_LOG(GetTimerFiringsLog(), LogLevel::Debug,
+              ("[%d]   obs timer (%s %5d ms): %p\n", getpid(), typeStr, aDelay,
+               aCallback.mCallback.o));
+      break;
+    }
+
+    case Callback::Type::Unknown:
+    default: {
+      MOZ_LOG(GetTimerFiringsLog(), LogLevel::Debug,
+              ("[%d]   ??? timer (%s, %5d ms)\n", getpid(), typeStr, aDelay));
+      break;
+    }
+  }
+}
+
+void nsTimerImpl::GetName(nsACString& aName) {
+  MutexAutoLock lock(mMutex);
+  Callback& cb(GetCallback());
+  switch (cb.mType) {
+    case Callback::Type::Function:
+      if (cb.mName.is<Callback::NameString>()) {
+        aName.Assign(cb.mName.as<Callback::NameString>());
+      } else if (cb.mName.is<Callback::NameFunc>()) {
+        static const size_t buflen = 1024;
+        char buf[buflen];
+        cb.mName.as<Callback::NameFunc>()(mITimer, /* aAnonymize = */ true,
+                                          cb.mClosure, buf, buflen);
+        aName.Assign(buf);
+      } else {
+        MOZ_ASSERT(cb.mName.is<Callback::NameNothing>());
+        aName.AssignLiteral("Anonymous_callback_timer");
+      }
+      break;
+
+    case Callback::Type::Interface:
+      if (nsCOMPtr<nsINamed> named = do_QueryInterface(cb.mCallback.i)) {
+        named->GetName(aName);
+      } else {
+        aName.AssignLiteral("Anonymous_interface_timer");
+      }
+      break;
+
+    case Callback::Type::Observer:
+      if (nsCOMPtr<nsINamed> named = do_QueryInterface(cb.mCallback.o)) {
+        named->GetName(aName);
+      } else {
+        aName.AssignLiteral("Anonymous_observer_timer");
+      }
+      break;
+
+    case Callback::Type::Unknown:
+      aName.AssignLiteral("Canceled_timer");
+      break;
+  }
+}
+
+void nsTimerImpl::SetHolder(nsTimerImplHolder* aHolder) { mHolder = aHolder; }
+
+nsTimer::~nsTimer() = default;
+
+size_t nsTimer::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const {
+  return aMallocSizeOf(this);
+}
+
+/* static */
+RefPtr<nsTimer> nsTimer::WithEventTarget(nsIEventTarget* aTarget) {
+  if (!aTarget) {
+    aTarget = mozilla::GetCurrentSerialEventTarget();
+  }
+  return do_AddRef(new nsTimer(aTarget));
+}
+
+/* static */
+nsresult nsTimer::XPCOMConstructor(nsISupports* aOuter, REFNSIID aIID,
+                                   void** aResult) {
+  *aResult = nullptr;
+  if (aOuter != nullptr) {
+    return NS_ERROR_NO_AGGREGATION;
+  }
+
+  auto timer = WithEventTarget(nullptr);
+
+  return timer->QueryInterface(aIID, aResult);
+}
+
+/* static */
+const nsTimerImpl::Callback::NameNothing nsTimerImpl::Callback::Nothing = 0;
+
+#ifdef MOZ_TASK_TRACER
+void nsTimerImpl::GetTLSTraceInfo() { mTracedTask.GetTLSTraceInfo(); }
+
+TracedTaskCommon nsTimerImpl::GetTracedTask() { return mTracedTask; }
+
+#endif