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diff --git a/tools/profiler/core/platform-win32.cpp b/tools/profiler/core/platform-win32.cpp
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+++ b/tools/profiler/core/platform-win32.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2006-2011 The Chromium Authors. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+//  * Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//  * Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in
+//    the documentation and/or other materials provided with the
+//    distribution.
+//  * Neither the name of Google, Inc. nor the names of its contributors
+//    may be used to endorse or promote products derived from this
+//    software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+// SUCH DAMAGE.
+
+#include <windows.h>
+#include <mmsystem.h>
+#include <process.h>
+
+#include "mozilla/WindowsVersion.h"
+
+#include <type_traits>
+
+static void PopulateRegsFromContext(Registers& aRegs, CONTEXT* aContext) {
+#if defined(GP_ARCH_amd64)
+  aRegs.mPC = reinterpret_cast<Address>(aContext->Rip);
+  aRegs.mSP = reinterpret_cast<Address>(aContext->Rsp);
+  aRegs.mFP = reinterpret_cast<Address>(aContext->Rbp);
+  aRegs.mR10 = reinterpret_cast<Address>(aContext->R10);
+  aRegs.mR12 = reinterpret_cast<Address>(aContext->R12);
+#elif defined(GP_ARCH_x86)
+  aRegs.mPC = reinterpret_cast<Address>(aContext->Eip);
+  aRegs.mSP = reinterpret_cast<Address>(aContext->Esp);
+  aRegs.mFP = reinterpret_cast<Address>(aContext->Ebp);
+  aRegs.mEcx = reinterpret_cast<Address>(aContext->Ecx);
+  aRegs.mEdx = reinterpret_cast<Address>(aContext->Edx);
+#elif defined(GP_ARCH_arm64)
+  aRegs.mPC = reinterpret_cast<Address>(aContext->Pc);
+  aRegs.mSP = reinterpret_cast<Address>(aContext->Sp);
+  aRegs.mFP = reinterpret_cast<Address>(aContext->Fp);
+  aRegs.mLR = reinterpret_cast<Address>(aContext->Lr);
+  aRegs.mR11 = reinterpret_cast<Address>(aContext->X11);
+#else
+#  error "bad arch"
+#endif
+}
+
+// Gets a real (i.e. not pseudo) handle for the current thread, with the
+// permissions needed for profiling.
+// @return a real HANDLE for the current thread.
+static HANDLE GetRealCurrentThreadHandleForProfiling() {
+  HANDLE realCurrentThreadHandle;
+  if (!::DuplicateHandle(
+          ::GetCurrentProcess(), ::GetCurrentThread(), ::GetCurrentProcess(),
+          &realCurrentThreadHandle,
+          THREAD_GET_CONTEXT | THREAD_SUSPEND_RESUME | THREAD_QUERY_INFORMATION,
+          FALSE, 0)) {
+    return nullptr;
+  }
+
+  return realCurrentThreadHandle;
+}
+
+static_assert(
+    std::is_same_v<mozilla::profiler::PlatformData::WindowsHandle, HANDLE>);
+
+mozilla::profiler::PlatformData::PlatformData(ProfilerThreadId aThreadId)
+    : mProfiledThread(GetRealCurrentThreadHandleForProfiling()) {
+  MOZ_ASSERT(aThreadId == ProfilerThreadId::FromNumber(::GetCurrentThreadId()));
+}
+
+mozilla::profiler::PlatformData::~PlatformData() {
+  if (mProfiledThread) {
+    CloseHandle(mProfiledThread);
+    mProfiledThread = nullptr;
+  }
+}
+
+static const HANDLE kNoThread = INVALID_HANDLE_VALUE;
+
+////////////////////////////////////////////////////////////////////////
+// BEGIN Sampler target specifics
+
+Sampler::Sampler(PSLockRef aLock) {}
+
+void Sampler::Disable(PSLockRef aLock) {}
+
+static void StreamMetaPlatformSampleUnits(PSLockRef aLock,
+                                          SpliceableJSONWriter& aWriter) {
+  static const Span<const char> units =
+      (GetCycleTimeFrequencyMHz() != 0) ? MakeStringSpan("ns")
+                                        : MakeStringSpan("variable CPU cycles");
+  aWriter.StringProperty("threadCPUDelta", units);
+}
+
+/* static */
+uint64_t RunningTimes::ConvertRawToJson(uint64_t aRawValue) {
+  static const uint64_t cycleTimeFrequencyMHz = GetCycleTimeFrequencyMHz();
+  if (cycleTimeFrequencyMHz == 0u) {
+    return aRawValue;
+  }
+
+  constexpr uint64_t GHZ_PER_MHZ = 1'000u;
+  // To get ns, we need to divide cycles by a frequency in GHz, i.e.:
+  // cycles / (f_MHz / GHZ_PER_MHZ). To avoid losing the integer precision of
+  // f_MHz, this is computed as (cycles * GHZ_PER_MHZ) / f_MHz.
+  // Adding GHZ_PER_MHZ/2 to (cycles * GHZ_PER_MHZ) will round to nearest when
+  // the result of the division is truncated.
+  return (aRawValue * GHZ_PER_MHZ + (GHZ_PER_MHZ / 2u)) / cycleTimeFrequencyMHz;
+}
+
+static inline uint64_t ToNanoSeconds(const FILETIME& aFileTime) {
+  // FILETIME values are 100-nanoseconds units, converting
+  ULARGE_INTEGER usec = {{aFileTime.dwLowDateTime, aFileTime.dwHighDateTime}};
+  return usec.QuadPart * 100;
+}
+
+namespace mozilla::profiler {
+bool GetCpuTimeSinceThreadStartInNs(
+    uint64_t* aResult, const mozilla::profiler::PlatformData& aPlatformData) {
+  const HANDLE profiledThread = aPlatformData.ProfiledThread();
+  int frequencyInMHz = GetCycleTimeFrequencyMHz();
+  if (frequencyInMHz) {
+    uint64_t cpuCycleCount;
+    if (!QueryThreadCycleTime(profiledThread, &cpuCycleCount)) {
+      return false;
+    }
+
+    constexpr uint64_t USEC_PER_NSEC = 1000L;
+    *aResult = cpuCycleCount * USEC_PER_NSEC / frequencyInMHz;
+    return true;
+  }
+
+  FILETIME createTime, exitTime, kernelTime, userTime;
+  if (!GetThreadTimes(profiledThread, &createTime, &exitTime, &kernelTime,
+                      &userTime)) {
+    return false;
+  }
+
+  *aResult = ToNanoSeconds(kernelTime) + ToNanoSeconds(userTime);
+  return true;
+}
+}  // namespace mozilla::profiler
+
+static RunningTimes GetProcessRunningTimesDiff(
+    PSLockRef aLock, RunningTimes& aPreviousRunningTimesToBeUpdated) {
+  AUTO_PROFILER_STATS(GetProcessRunningTimes);
+
+  static const HANDLE processHandle = GetCurrentProcess();
+
+  RunningTimes newRunningTimes;
+  {
+    AUTO_PROFILER_STATS(GetProcessRunningTimes_QueryProcessCycleTime);
+    if (ULONG64 cycles; QueryProcessCycleTime(processHandle, &cycles) != 0) {
+      newRunningTimes.SetThreadCPUDelta(cycles);
+    }
+    newRunningTimes.SetPostMeasurementTimeStamp(TimeStamp::Now());
+  };
+
+  const RunningTimes diff = newRunningTimes - aPreviousRunningTimesToBeUpdated;
+  aPreviousRunningTimesToBeUpdated = newRunningTimes;
+  return diff;
+}
+
+static RunningTimes GetThreadRunningTimesDiff(
+    PSLockRef aLock,
+    ThreadRegistration::UnlockedRWForLockedProfiler& aThreadData) {
+  AUTO_PROFILER_STATS(GetThreadRunningTimes);
+
+  const mozilla::profiler::PlatformData& platformData =
+      aThreadData.PlatformDataCRef();
+  const HANDLE profiledThread = platformData.ProfiledThread();
+
+  const RunningTimes newRunningTimes = GetRunningTimesWithTightTimestamp(
+      [profiledThread](RunningTimes& aRunningTimes) {
+        AUTO_PROFILER_STATS(GetThreadRunningTimes_QueryThreadCycleTime);
+        if (ULONG64 cycles;
+            QueryThreadCycleTime(profiledThread, &cycles) != 0) {
+          aRunningTimes.ResetThreadCPUDelta(cycles);
+        } else {
+          aRunningTimes.ClearThreadCPUDelta();
+        }
+      });
+
+  ProfiledThreadData* profiledThreadData =
+      aThreadData.GetProfiledThreadData(aLock);
+  MOZ_ASSERT(profiledThreadData);
+  RunningTimes& previousRunningTimes =
+      profiledThreadData->PreviousThreadRunningTimesRef();
+  const RunningTimes diff = newRunningTimes - previousRunningTimes;
+  previousRunningTimes = newRunningTimes;
+  return diff;
+}
+
+static void DiscardSuspendedThreadRunningTimes(
+    PSLockRef aLock,
+    ThreadRegistration::UnlockedRWForLockedProfiler& aThreadData) {
+  AUTO_PROFILER_STATS(DiscardSuspendedThreadRunningTimes);
+
+  // On Windows, suspending a thread makes that thread work a little bit. So we
+  // want to discard any added running time since the call to
+  // GetThreadRunningTimesDiff, which is done by overwriting the thread's
+  // PreviousThreadRunningTimesRef() with the current running time now.
+
+  const mozilla::profiler::PlatformData& platformData =
+      aThreadData.PlatformDataCRef();
+  const HANDLE profiledThread = platformData.ProfiledThread();
+
+  ProfiledThreadData* profiledThreadData =
+      aThreadData.GetProfiledThreadData(aLock);
+  MOZ_ASSERT(profiledThreadData);
+  RunningTimes& previousRunningTimes =
+      profiledThreadData->PreviousThreadRunningTimesRef();
+
+  if (ULONG64 cycles; QueryThreadCycleTime(profiledThread, &cycles) != 0) {
+    previousRunningTimes.ResetThreadCPUDelta(cycles);
+  } else {
+    previousRunningTimes.ClearThreadCPUDelta();
+  }
+}
+
+template <typename Func>
+void Sampler::SuspendAndSampleAndResumeThread(
+    PSLockRef aLock,
+    const ThreadRegistration::UnlockedReaderAndAtomicRWOnThread& aThreadData,
+    const TimeStamp& aNow, const Func& aProcessRegs) {
+  HANDLE profiled_thread = aThreadData.PlatformDataCRef().ProfiledThread();
+  if (profiled_thread == nullptr) {
+    return;
+  }
+
+  // Context used for sampling the register state of the profiled thread.
+  CONTEXT context;
+  memset(&context, 0, sizeof(context));
+
+  //----------------------------------------------------------------//
+  // Suspend the samplee thread and get its context.
+
+  static const DWORD kSuspendFailed = static_cast<DWORD>(-1);
+  if (SuspendThread(profiled_thread) == kSuspendFailed) {
+    return;
+  }
+
+  // SuspendThread is asynchronous, so the thread may still be running.
+  // Call GetThreadContext first to ensure the thread is really suspended.
+  // See https://blogs.msdn.microsoft.com/oldnewthing/20150205-00/?p=44743.
+
+  // Using only CONTEXT_CONTROL is faster but on 64-bit it causes crashes in
+  // RtlVirtualUnwind (see bug 1120126) so we set all the flags.
+#if defined(GP_ARCH_amd64)
+  context.ContextFlags = CONTEXT_FULL;
+#else
+  context.ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER;
+#endif
+  if (!GetThreadContext(profiled_thread, &context)) {
+    ResumeThread(profiled_thread);
+    return;
+  }
+
+  //----------------------------------------------------------------//
+  // Sample the target thread.
+
+  // WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+  //
+  // The profiler's "critical section" begins here.  We must be very careful
+  // what we do here, or risk deadlock.  See the corresponding comment in
+  // platform-linux-android.cpp for details.
+
+  Registers regs;
+  PopulateRegsFromContext(regs, &context);
+  aProcessRegs(regs, aNow);
+
+  //----------------------------------------------------------------//
+  // Resume the target thread.
+
+  ResumeThread(profiled_thread);
+
+  // The profiler's critical section ends here.
+  //
+  // WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
+}
+
+// END Sampler target specifics
+////////////////////////////////////////////////////////////////////////
+
+////////////////////////////////////////////////////////////////////////
+// BEGIN SamplerThread target specifics
+
+static unsigned int __stdcall ThreadEntry(void* aArg) {
+  auto thread = static_cast<SamplerThread*>(aArg);
+  thread->Run();
+  return 0;
+}
+
+static unsigned int __stdcall UnregisteredThreadSpyEntry(void* aArg) {
+  auto thread = static_cast<SamplerThread*>(aArg);
+  thread->RunUnregisteredThreadSpy();
+  return 0;
+}
+
+SamplerThread::SamplerThread(PSLockRef aLock, uint32_t aActivityGeneration,
+                             double aIntervalMilliseconds, uint32_t aFeatures)
+    : mSampler(aLock),
+      mActivityGeneration(aActivityGeneration),
+      mIntervalMicroseconds(
+          std::max(1, int(floor(aIntervalMilliseconds * 1000 + 0.5)))),
+      mNoTimerResolutionChange(
+          ProfilerFeature::HasNoTimerResolutionChange(aFeatures)) {
+  if ((!mNoTimerResolutionChange) && (mIntervalMicroseconds < 10 * 1000)) {
+    // By default the timer resolution (which tends to be 1/64Hz, around 16ms)
+    // is not changed. However, if the requested interval is sufficiently low,
+    // the resolution will be adjusted to match. Note that this affects all
+    // timers in Firefox, and could therefore hide issues while profiling. This
+    // change may be prevented with the "notimerresolutionchange" feature.
+    ::timeBeginPeriod(mIntervalMicroseconds / 1000);
+  }
+
+  if (ProfilerFeature::HasUnregisteredThreads(aFeatures)) {
+    // Sampler&spy threads are not running yet, so it's safe to modify
+    // mSpyingState without locking the monitor.
+    mSpyingState = SpyingState::Spy_Initializing;
+    mUnregisteredThreadSpyThread = reinterpret_cast<HANDLE>(
+        _beginthreadex(nullptr,
+                       /* stack_size */ 0, UnregisteredThreadSpyEntry, this,
+                       /* initflag */ 0, nullptr));
+    if (mUnregisteredThreadSpyThread == 0) {
+      MOZ_CRASH("_beginthreadex failed");
+    }
+  }
+
+  // Create a new thread. It is important to use _beginthreadex() instead of
+  // the Win32 function CreateThread(), because the CreateThread() does not
+  // initialize thread-specific structures in the C runtime library.
+  mThread = reinterpret_cast<HANDLE>(_beginthreadex(nullptr,
+                                                    /* stack_size */ 0,
+                                                    ThreadEntry, this,
+                                                    /* initflag */ 0, nullptr));
+  if (mThread == 0) {
+    MOZ_CRASH("_beginthreadex failed");
+  }
+}
+
+SamplerThread::~SamplerThread() {
+  if (mUnregisteredThreadSpyThread) {
+    {
+      // Make sure the spying thread is not actively working, because the win32
+      // function it's using could deadlock with WaitForSingleObject below.
+      MonitorAutoLock spyingStateLock{mSpyingStateMonitor};
+      while (mSpyingState != SpyingState::Spy_Waiting &&
+             mSpyingState != SpyingState::SamplerToSpy_Start) {
+        spyingStateLock.Wait();
+      }
+
+      mSpyingState = SpyingState::MainToSpy_Shutdown;
+      spyingStateLock.NotifyAll();
+
+      do {
+        spyingStateLock.Wait();
+      } while (mSpyingState != SpyingState::SpyToMain_ShuttingDown);
+    }
+
+    WaitForSingleObject(mUnregisteredThreadSpyThread, INFINITE);
+
+    // Close our own handle for the thread.
+    if (mUnregisteredThreadSpyThread != kNoThread) {
+      CloseHandle(mUnregisteredThreadSpyThread);
+    }
+  }
+
+  WaitForSingleObject(mThread, INFINITE);
+
+  // Close our own handle for the thread.
+  if (mThread != kNoThread) {
+    CloseHandle(mThread);
+  }
+
+  // Just in the unlikely case some callbacks were added between the end of the
+  // thread and now.
+  InvokePostSamplingCallbacks(std::move(mPostSamplingCallbackList),
+                              SamplingState::JustStopped);
+}
+
+void SamplerThread::RunUnregisteredThreadSpy() {
+  // TODO: Consider registering this thread.
+  // Pros: Remove from list of unregistered threads; Not useful to profiling
+  //       Firefox itself.
+  // Cons: Doesn't appear in the profile, so users may miss the expensive CPU
+  //       cost of this work on Windows.
+  PR_SetCurrentThreadName("UnregisteredThreadSpy");
+
+  while (true) {
+    {
+      MonitorAutoLock spyingStateLock{mSpyingStateMonitor};
+      // Either this is the first loop, or we're looping after working.
+      MOZ_ASSERT(mSpyingState == SpyingState::Spy_Initializing ||
+                 mSpyingState == SpyingState::Spy_Working);
+
+      // Let everyone know we're waiting, and then wait.
+      mSpyingState = SpyingState::Spy_Waiting;
+      mSpyingStateMonitor.NotifyAll();
+      do {
+        spyingStateLock.Wait();
+      } while (mSpyingState == SpyingState::Spy_Waiting);
+
+      if (mSpyingState == SpyingState::MainToSpy_Shutdown) {
+        mSpyingState = SpyingState::SpyToMain_ShuttingDown;
+        mSpyingStateMonitor.NotifyAll();
+        break;
+      }
+
+      MOZ_ASSERT(mSpyingState == SpyingState::SamplerToSpy_Start);
+      mSpyingState = SpyingState::Spy_Working;
+    }
+
+    // Do the work without lock, so other threads can read the current state.
+    SpyOnUnregisteredThreads();
+  }
+}
+
+void SamplerThread::SleepMicro(uint32_t aMicroseconds) {
+  // For now, keep the old behaviour of minimum Sleep(1), even for
+  // smaller-than-usual sleeps after an overshoot, unless the user has
+  // explicitly opted into a sub-millisecond profiler interval.
+  if (mIntervalMicroseconds >= 1000) {
+    ::Sleep(std::max(1u, aMicroseconds / 1000));
+  } else {
+    TimeStamp start = TimeStamp::Now();
+    TimeStamp end = start + TimeDuration::FromMicroseconds(aMicroseconds);
+
+    // First, sleep for as many whole milliseconds as possible.
+    if (aMicroseconds >= 1000) {
+      ::Sleep(aMicroseconds / 1000);
+    }
+
+    // Then, spin until enough time has passed.
+    while (TimeStamp::Now() < end) {
+      YieldProcessor();
+    }
+  }
+}
+
+void SamplerThread::Stop(PSLockRef aLock) {
+  if ((!mNoTimerResolutionChange) && (mIntervalMicroseconds < 10 * 1000)) {
+    // Disable any timer resolution changes we've made. Do it now while
+    // gPSMutex is locked, i.e. before any other SamplerThread can be created
+    // and call ::timeBeginPeriod().
+    //
+    // It's safe to do this now even though this SamplerThread is still alive,
+    // because the next time the main loop of Run() iterates it won't get past
+    // the mActivityGeneration check, and so it won't make any more ::Sleep()
+    // calls.
+    ::timeEndPeriod(mIntervalMicroseconds / 1000);
+  }
+
+  mSampler.Disable(aLock);
+}
+
+// END SamplerThread target specifics
+////////////////////////////////////////////////////////////////////////
+
+static void PlatformInit(PSLockRef aLock) {}
+
+#if defined(HAVE_NATIVE_UNWIND)
+#  define REGISTERS_SYNC_POPULATE(regs) \
+    CONTEXT context;                    \
+    RtlCaptureContext(&context);        \
+    PopulateRegsFromContext(regs, &context);
+#endif