Issue #21 - Remove Telemetry plumbing and fix build.

Note this won't give working applications. Requires FE changes and
additional js module changes (next part).

9 files changed, 9 insertions, 550 deletions

diff --git a/xpcom/base/CycleCollectedJSContext.cpp b/xpcom/base/CycleCollectedJSContext.cpp
index 0a4c2da4fa..17a989c833 100644
--- a/xpcom/base/CycleCollectedJSContext.cpp
+++ b/xpcom/base/CycleCollectedJSContext.cpp
@@ -60,7 +60,6 @@
 #include "mozilla/Move.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Sprintf.h"
-#include "mozilla/Telemetry.h"
 #include "mozilla/TimelineConsumers.h"
 #include "mozilla/TimelineMarker.h"
 #include "mozilla/Unused.h"
diff --git a/xpcom/base/nsMemoryReporterManager.cpp b/xpcom/base/nsMemoryReporterManager.cpp
index 810254bcc6..4397f470e8 100644
--- a/xpcom/base/nsMemoryReporterManager.cpp
+++ b/xpcom/base/nsMemoryReporterManager.cpp
@@ -23,7 +23,6 @@
 #include "mozilla/PodOperations.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Services.h"
-#include "mozilla/Telemetry.h"
 #include "mozilla/UniquePtrExtensions.h"
 #include "mozilla/dom/PMemoryReportRequestParent.h" // for dom::MemoryReport
 #include "mozilla/dom/ContentParent.h"
diff --git a/xpcom/build/LateWriteChecks.cpp b/xpcom/build/LateWriteChecks.cpp
index daa18c0d5e..7ace9a0fbd 100644
--- a/xpcom/build/LateWriteChecks.cpp
+++ b/xpcom/build/LateWriteChecks.cpp
@@ -7,11 +7,9 @@
 
 #include "mozilla/IOInterposer.h"
 #include "mozilla/PoisonIOInterposer.h"
-#include "mozilla/ProcessedStack.h"
 #include "mozilla/SHA1.h"
 #include "mozilla/Scoped.h"
 #include "mozilla/StaticPtr.h"
-#include "mozilla/Telemetry.h"
 #include "nsAppDirectoryServiceDefs.h"
 #include "nsDirectoryServiceUtils.h"
 #include "nsPrintfCString.h"
@@ -34,8 +32,6 @@
 
 #include "LateWriteChecks.h"
 
-#define OBSERVE_LATE_WRITES
-
 using namespace mozilla;
 
 /*************************** Auxiliary Declarations ***************************/
@@ -111,102 +107,7 @@ private:
 void
 LateWriteObserver::Observe(IOInterposeObserver::Observation& aOb)
 {
-#ifdef OBSERVE_LATE_WRITES
-  // Crash if that is the shutdown check mode
-  if (gShutdownChecks == SCM_CRASH) {
-    MOZ_CRASH();
-  }
-
-  // If we have shutdown mode SCM_NOTHING or we can't record then abort
-  if (gShutdownChecks == SCM_NOTHING || !Telemetry::CanRecordExtended()) {
-    return;
-  }
-
-  // Write the stack and loaded libraries to a file. We can get here
-  // concurrently from many writes, so we use multiple temporary files.
-  std::vector<uintptr_t> rawStack;
-
-  MozStackWalk(RecordStackWalker, /* skipFrames */ 0, /* maxFrames */ 0,
-               reinterpret_cast<void*>(&rawStack), 0, nullptr);
-  Telemetry::ProcessedStack stack = Telemetry::GetStackAndModules(rawStack);
-
-  nsPrintfCString nameAux("%s%s%s", mProfileDirectory,
-                          NS_SLASH, "Telemetry.LateWriteTmpXXXXXX");
-  char* name;
-  nameAux.GetMutableData(&name);
-
-  // We want the sha1 of the entire file, so please don't write to fd
-  // directly; use sha1Stream.
-  FILE* stream;
-#ifdef XP_WIN
-  HANDLE hFile;
-  do {
-    // mkstemp isn't supported so keep trying until we get a file
-    int result = _mktemp_s(name, strlen(name) + 1);
-    hFile = CreateFileA(name, GENERIC_WRITE, 0, nullptr, CREATE_NEW,
-                        FILE_ATTRIBUTE_NORMAL, nullptr);
-  } while (GetLastError() == ERROR_FILE_EXISTS);
-
-  if (hFile == INVALID_HANDLE_VALUE) {
-    NS_RUNTIMEABORT("Um, how did we get here?");
-  }
-
-  // http://support.microsoft.com/kb/139640
-  int fd = _open_osfhandle((intptr_t)hFile, _O_APPEND);
-  if (fd == -1) {
-    NS_RUNTIMEABORT("Um, how did we get here?");
-  }
-
-  stream = _fdopen(fd, "w");
-#else
-  int fd = mkstemp(name);
-  stream = fdopen(fd, "w");
-#endif
-
-  SHA1Stream sha1Stream(stream);
-
-  size_t numModules = stack.GetNumModules();
-  sha1Stream.Printf("%u\n", (unsigned)numModules);
-  for (size_t i = 0; i < numModules; ++i) {
-    Telemetry::ProcessedStack::Module module = stack.GetModule(i);
-    sha1Stream.Printf("%s %s\n", module.mBreakpadId.c_str(),
-                      module.mName.c_str());
-  }
-
-  size_t numFrames = stack.GetStackSize();
-  sha1Stream.Printf("%u\n", (unsigned)numFrames);
-  for (size_t i = 0; i < numFrames; ++i) {
-    const Telemetry::ProcessedStack::Frame& frame = stack.GetFrame(i);
-    // NOTE: We write the offsets, while the atos tool expects a value with
-    // the virtual address added. For example, running otool -l on the the firefox
-    // binary shows
-    //      cmd LC_SEGMENT_64
-    //      cmdsize 632
-    //      segname __TEXT
-    //      vmaddr 0x0000000100000000
-    // so to print the line matching the offset 123 one has to run
-    // atos -o firefox 0x100000123.
-    sha1Stream.Printf("%d %x\n", frame.mModIndex, (unsigned)frame.mOffset);
-  }
-
-  SHA1Sum::Hash sha1;
-  sha1Stream.Finish(sha1);
-
-  // Note: These files should be deleted by telemetry once it reads them. If
-  // there were no telemetry runs by the time we shut down, we just add files
-  // to the existing ones instead of replacing them. Given that each of these
-  // files is a bug to be fixed, that is probably the right thing to do.
-
-  // We append the sha1 of the contents to the file name. This provides a simple
-  // client side deduplication.
-  nsPrintfCString finalName("%s%s", mProfileDirectory,
-                            "/Telemetry.LateWriteFinal-");
-  for (int i = 0; i < 20; ++i) {
-    finalName.AppendPrintf("%02x", sha1[i]);
-  }
-  PR_Delete(finalName.get());
-  PR_Rename(name, finalName.get());
-#endif
+/* *** STUB *** */
 }
 
 /******************************* Setup/Teardown *******************************/
diff --git a/xpcom/build/XPCOMInit.cpp b/xpcom/build/XPCOMInit.cpp
index e96314a1c5..3291c06c07 100644
--- a/xpcom/build/XPCOMInit.cpp
+++ b/xpcom/build/XPCOMInit.cpp
@@ -131,7 +131,6 @@ extern nsresult nsStringInputStreamConstructor(nsISupports*, REFNSIID, void**);
 #include "mozilla/Services.h"
 #include "mozilla/Omnijar.h"
 #include "mozilla/HangMonitor.h"
-#include "mozilla/Telemetry.h"
 #include "mozilla/BackgroundHangMonitor.h"
 
 #include "nsChromeRegistry.h"
@@ -757,8 +756,6 @@ NS_InitXPCOM2(nsIServiceManager** aResult,
   RegisterStrongMemoryReporter(new VPXReporter());
 #endif
 
-  mozilla::Telemetry::Init();
-
   mozilla::HangMonitor::Startup();
   mozilla::BackgroundHangMonitor::Startup();
 
@@ -812,7 +809,6 @@ NS_InitMinimalXPCOM()
 
   AbstractThread::InitStatics();
   SharedThreadPool::InitStatics();
-  mozilla::Telemetry::Init();
   mozilla::HangMonitor::Startup();
   mozilla::BackgroundHangMonitor::Startup();
 
diff --git a/xpcom/threads/BackgroundHangMonitor.cpp b/xpcom/threads/BackgroundHangMonitor.cpp
index 7af342c8c9..b0b41e291e 100644
--- a/xpcom/threads/BackgroundHangMonitor.cpp
+++ b/xpcom/threads/BackgroundHangMonitor.cpp
@@ -10,13 +10,10 @@
 #include "mozilla/Move.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/StaticPtr.h"
-#include "mozilla/Telemetry.h"
-#include "mozilla/ThreadHangStats.h"
 #include "mozilla/ThreadLocal.h"
 
 #include "prinrval.h"
 #include "prthread.h"
-#include "ThreadStackHelper.h"
 #include "nsIObserverService.h"
 #include "nsIObserver.h"
 #include "mozilla/Services.h"
@@ -30,7 +27,7 @@
 #define BHR_BETA_MOD 1;
 
 // Maximum depth of the call stack in the reported thread hangs. This value represents
-// the 99.9th percentile of the thread hangs stack depths reported by Telemetry.
+// the 99.9th percentile of the thread hangs stack depths reported.
 static const size_t kMaxThreadHangStackDepth = 30;
 
 // An utility comparator function used by std::unique to collapse "(* script)" entries in
@@ -174,12 +171,6 @@ public:
   bool mWaiting;
   // Is the thread dedicated to a single BackgroundHangMonitor
   BackgroundHangMonitor::ThreadType mThreadType;
-  // Platform-specific helper to get hang stacks
-  ThreadStackHelper mStackHelper;
-  // Stack of current hang
-  Telemetry::HangStack mHangStack;
-  // Statistics for telemetry
-  Telemetry::ThreadHangStats mStats;
   // Annotations for the current hang
   UniquePtr<HangMonitor::HangAnnotations> mAnnotations;
   // Annotators registered for this thread
@@ -190,10 +181,6 @@ public:
                        uint32_t aMaxTimeoutMs,
                        BackgroundHangMonitor::ThreadType aThreadType = BackgroundHangMonitor::THREAD_SHARED);
 
-  // Report a hang; aManager->mLock IS locked
-  Telemetry::HangHistogram& ReportHang(PRIntervalTime aHangTime);
-  // Report a permanent hang; aManager->mLock IS locked
-  void ReportPermaHang();
   // Called by BackgroundHangMonitor::NotifyActivity
   void NotifyActivity()
   {
@@ -325,14 +312,12 @@ BackgroundHangManager::RunMonitorThread()
         // Skip subsequent iterations and tolerate a race on mWaiting here
         currentThread->mWaiting = true;
         currentThread->mHanging = false;
-        currentThread->ReportPermaHang();
         continue;
       }
 
       if (MOZ_LIKELY(!currentThread->mHanging)) {
         if (MOZ_UNLIKELY(hangTime >= currentThread->mTimeout)) {
           // A hang started
-          currentThread->mStackHelper.GetStack(currentThread->mHangStack);
           currentThread->mHangStart = interval;
           currentThread->mHanging = true;
           currentThread->mAnnotations =
@@ -341,7 +326,6 @@ BackgroundHangManager::RunMonitorThread()
       } else {
         if (MOZ_LIKELY(interval != currentThread->mHangStart)) {
           // A hang ended
-          currentThread->ReportHang(intervalNow - currentThread->mHangStart);
           currentThread->mHanging = false;
         }
       }
@@ -390,7 +374,6 @@ BackgroundHangThread::BackgroundHangThread(const char* aName,
   , mHanging(false)
   , mWaiting(true)
   , mThreadType(aThreadType)
-  , mStats(aName)
 {
   if (sTlsKeyInitialized && IsShared()) {
     sTlsKey.set(this);
@@ -416,69 +399,6 @@ BackgroundHangThread::~BackgroundHangThread()
   if (sTlsKeyInitialized && IsShared()) {
     sTlsKey.set(nullptr);
   }
-
-  // Move our copy of ThreadHangStats to Telemetry storage
-  Telemetry::RecordThreadHangStats(mStats);
-}
-
-Telemetry::HangHistogram&
-BackgroundHangThread::ReportHang(PRIntervalTime aHangTime)
-{
-  // Recovered from a hang; called on the monitor thread
-  // mManager->mLock IS locked
-
-  // Remove unwanted "js::RunScript" frame from the stack
-  for (size_t i = 0; i < mHangStack.length(); ) {
-    const char** f = mHangStack.begin() + i;
-    if (!mHangStack.IsInBuffer(*f) && !strcmp(*f, "js::RunScript")) {
-      mHangStack.erase(f);
-    } else {
-      i++;
-    }
-  }
-
-  // Collapse duplicated "(chrome script)" and "(content script)" entries in the stack.
-  auto it = std::unique(mHangStack.begin(), mHangStack.end(), StackScriptEntriesCollapser);
-  mHangStack.erase(it, mHangStack.end());
-
-  // Limit the depth of the reported stack if greater than our limit. Only keep its
-  // last entries, since the most recent frames are at the end of the vector.
-  if (mHangStack.length() > kMaxThreadHangStackDepth) {
-    const int elementsToRemove = mHangStack.length() - kMaxThreadHangStackDepth;
-    // Replace the oldest frame with a known label so that we can tell this stack
-    // was limited.
-    mHangStack[0] = "(reduced stack)";
-    mHangStack.erase(mHangStack.begin() + 1, mHangStack.begin() + elementsToRemove);
-  }
-
-  Telemetry::HangHistogram newHistogram(Move(mHangStack));
-  for (Telemetry::HangHistogram* oldHistogram = mStats.mHangs.begin();
-       oldHistogram != mStats.mHangs.end(); oldHistogram++) {
-    if (newHistogram == *oldHistogram) {
-      // New histogram matches old one
-      oldHistogram->Add(aHangTime, Move(mAnnotations));
-      return *oldHistogram;
-    }
-  }
-  // Add new histogram
-  newHistogram.Add(aHangTime, Move(mAnnotations));
-  if (!mStats.mHangs.append(Move(newHistogram))) {
-    MOZ_CRASH();
-  }
-  return mStats.mHangs.back();
-}
-
-void
-BackgroundHangThread::ReportPermaHang()
-{
-  // Permanently hanged; called on the monitor thread
-  // mManager->mLock IS locked
-
-  Telemetry::HangHistogram& hang = ReportHang(mMaxTimeout);
-  Telemetry::HangStack& stack = hang.GetNativeStack();
-  if (stack.empty()) {
-    mStackHelper.GetNativeStack(stack);
-  }
 }
 
 MOZ_ALWAYS_INLINE void
@@ -493,7 +413,6 @@ BackgroundHangThread::Update()
     mManager->Wakeup();
   } else {
     PRIntervalTime duration = intervalNow - mInterval;
-    mStats.mActivity.Add(duration);
     if (MOZ_UNLIKELY(duration >= mTimeout)) {
       /* Wake up the manager thread to tell it that a hang ended */
       mManager->Wakeup();
@@ -552,19 +471,12 @@ BackgroundHangMonitor::IsDisabled() {
 
 bool
 BackgroundHangMonitor::DisableOnBeta() {
-  nsAdoptingCString clientID = Preferences::GetCString("toolkit.telemetry.cachedClientID");
-  bool telemetryEnabled = Preferences::GetBool("toolkit.telemetry.enabled");
-
-  if (!telemetryEnabled || !clientID || BackgroundHangMonitor::ShouldDisableOnBeta(clientID)) {
-    if (XRE_IsParentProcess()) {
-      BackgroundHangMonitor::Shutdown();
-    } else {
-      BackgroundHangManager::sDisabled = true;
-    }
-    return true;
+  if (XRE_IsParentProcess()) {
+    BackgroundHangMonitor::Shutdown();
+  } else {
+    BackgroundHangManager::sDisabled = true;
   }
-
-  return false;
+  return true;
 }
 
 void
@@ -575,7 +487,6 @@ BackgroundHangMonitor::Startup()
 
   if (!strcmp(NS_STRINGIFY(MOZ_UPDATE_CHANNEL), "beta")) {
     if (XRE_IsParentProcess()) { // cached ClientID hasn't been read yet
-      ThreadStackHelper::Startup();
       BackgroundHangThread::Startup();
       BackgroundHangManager::sInstance = new BackgroundHangManager();
 
@@ -589,7 +500,6 @@ BackgroundHangMonitor::Startup()
     }
   }
 
-  ThreadStackHelper::Startup();
   BackgroundHangThread::Startup();
   BackgroundHangManager::sInstance = new BackgroundHangManager();
 #endif
@@ -610,7 +520,6 @@ BackgroundHangMonitor::Shutdown()
      we don't want to hold the lock when it's being destroyed. */
   BackgroundHangManager::sInstance->Shutdown();
   BackgroundHangManager::sInstance = nullptr;
-  ThreadStackHelper::Shutdown();
   BackgroundHangManager::sDisabled = true;
 #endif
 }
@@ -652,11 +561,8 @@ BackgroundHangMonitor::NotifyActivity()
                "This thread is not initialized for hang monitoring");
     return;
   }
-
-  if (Telemetry::CanRecordExtended()) {
-    mThread->NotifyActivity();
-  }
 #endif
+// STUB
 }
 
 void
@@ -668,11 +574,8 @@ BackgroundHangMonitor::NotifyWait()
                "This thread is not initialized for hang monitoring");
     return;
   }
-
-  if (Telemetry::CanRecordExtended()) {
-    mThread->NotifyWait();
-  }
 #endif
+// STUB
 }
 
 bool
@@ -719,15 +622,4 @@ BackgroundHangMonitor::ThreadHangStatsIterator::ThreadHangStatsIterator()
 #endif
 }
 
-Telemetry::ThreadHangStats*
-BackgroundHangMonitor::ThreadHangStatsIterator::GetNext()
-{
-  if (!mThread) {
-    return nullptr;
-  }
-  Telemetry::ThreadHangStats* stats = &mThread->mStats;
-  mThread = mThread->getNext();
-  return stats;
-}
-
 } // namespace mozilla
diff --git a/xpcom/threads/HangMonitor.cpp b/xpcom/threads/HangMonitor.cpp
index 1f512a28c0..1fd74066a0 100644
--- a/xpcom/threads/HangMonitor.cpp
+++ b/xpcom/threads/HangMonitor.cpp
@@ -9,8 +9,6 @@
 #include "mozilla/BackgroundHangMonitor.h"
 #include "mozilla/Monitor.h"
 #include "mozilla/Preferences.h"
-#include "mozilla/ProcessedStack.h"
-#include "mozilla/Telemetry.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/UniquePtr.h"
 #include "nsReadableUtils.h"
diff --git a/xpcom/threads/ThreadStackHelper.cpp b/xpcom/threads/ThreadStackHelper.cpp
deleted file mode 100644
index 72d82e4daa..0000000000
--- a/xpcom/threads/ThreadStackHelper.cpp
+++ /dev/null
@@ -1,225 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* 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 "ThreadStackHelper.h"
-#include "MainThreadUtils.h"
-#include "nsJSPrincipals.h"
-#include "nsScriptSecurityManager.h"
-#include "jsfriendapi.h"
-
-#include "mozilla/Assertions.h"
-#include "mozilla/Attributes.h"
-#include "mozilla/IntegerPrintfMacros.h"
-#include "mozilla/Move.h"
-#include "mozilla/Scoped.h"
-#include "mozilla/UniquePtr.h"
-#include "mozilla/MemoryChecking.h"
-#include "mozilla/Sprintf.h"
-
-#ifdef __GNUC__
-# pragma GCC diagnostic push
-# pragma GCC diagnostic ignored "-Wshadow"
-#endif
-
-#if defined(MOZ_VALGRIND)
-# include <valgrind/valgrind.h>
-#endif
-
-#include <string.h>
-#include <vector>
-#include <cstdlib>
-
-#ifdef XP_LINUX
-#include <ucontext.h>
-#include <unistd.h>
-#include <sys/syscall.h>
-#endif
-
-#ifdef __GNUC__
-# pragma GCC diagnostic pop // -Wshadow
-#endif
-
-#if defined(XP_LINUX)
-#include <pthread.h>
-#endif
-
-namespace mozilla {
-
-void
-ThreadStackHelper::Startup()
-{
-#if defined(XP_LINUX)
-  MOZ_ASSERT(NS_IsMainThread());
-  if (!sInitialized) {
-    // TODO: centralize signal number allocation
-    sFillStackSignum = SIGRTMIN + 4;
-    if (sFillStackSignum > SIGRTMAX) {
-      // Leave uninitialized
-      MOZ_ASSERT(false);
-      return;
-    }
-    struct sigaction sigact = {};
-    sigact.sa_sigaction = FillStackHandler;
-    sigemptyset(&sigact.sa_mask);
-    sigact.sa_flags = SA_SIGINFO | SA_RESTART;
-    MOZ_ALWAYS_TRUE(!::sigaction(sFillStackSignum, &sigact, nullptr));
-  }
-  sInitialized++;
-#endif
-}
-
-void
-ThreadStackHelper::Shutdown()
-{
-#if defined(XP_LINUX)
-  MOZ_ASSERT(NS_IsMainThread());
-  if (sInitialized == 1) {
-    struct sigaction sigact = {};
-    sigact.sa_handler = SIG_DFL;
-    MOZ_ALWAYS_TRUE(!::sigaction(sFillStackSignum, &sigact, nullptr));
-  }
-  sInitialized--;
-#endif
-}
-
-ThreadStackHelper::ThreadStackHelper()
-  : mStackToFill(nullptr)
-{
-#if defined(XP_LINUX)
-  MOZ_ALWAYS_TRUE(!::sem_init(&mSem, 0, 0));
-  mThreadID = ::syscall(SYS_gettid);
-#elif defined(XP_WIN)
-  mInitialized = !!::DuplicateHandle(
-    ::GetCurrentProcess(), ::GetCurrentThread(),
-    ::GetCurrentProcess(), &mThreadID,
-    THREAD_SUSPEND_RESUME
-    , FALSE, 0);
-  MOZ_ASSERT(mInitialized);
-#endif
-}
-
-ThreadStackHelper::~ThreadStackHelper()
-{
-#if defined(XP_LINUX)
-  MOZ_ALWAYS_TRUE(!::sem_destroy(&mSem));
-#elif defined(XP_WIN)
-  if (mInitialized) {
-    MOZ_ALWAYS_TRUE(!!::CloseHandle(mThreadID));
-  }
-#endif
-}
-
-namespace {
-template<typename T>
-class ScopedSetPtr
-{
-private:
-  T*& mPtr;
-public:
-  ScopedSetPtr(T*& p, T* val) : mPtr(p) { mPtr = val; }
-  ~ScopedSetPtr() { mPtr = nullptr; }
-};
-} // namespace
-
-void
-ThreadStackHelper::GetStack(Stack& aStack)
-{
-  // Always run PrepareStackBuffer first to clear aStack
-  if (!PrepareStackBuffer(aStack)) {
-    // Skip and return empty aStack
-    return;
-  }
-
-  ScopedSetPtr<Stack> stackPtr(mStackToFill, &aStack);
-
-#if defined(XP_LINUX)
-  if (!sInitialized) {
-    MOZ_ASSERT(false);
-    return;
-  }
-  siginfo_t uinfo = {};
-  uinfo.si_signo = sFillStackSignum;
-  uinfo.si_code = SI_QUEUE;
-  uinfo.si_pid = getpid();
-  uinfo.si_uid = getuid();
-  uinfo.si_value.sival_ptr = this;
-  if (::syscall(SYS_rt_tgsigqueueinfo, uinfo.si_pid,
-                mThreadID, sFillStackSignum, &uinfo)) {
-    // rt_tgsigqueueinfo was added in Linux 2.6.31.
-    // Could have failed because the syscall did not exist.
-    return;
-  }
-  MOZ_ALWAYS_TRUE(!::sem_wait(&mSem));
-
-#elif defined(XP_WIN)
-  if (!mInitialized) {
-    MOZ_ASSERT(false);
-    return;
-  }
-  if (::SuspendThread(mThreadID) == DWORD(-1)) {
-    MOZ_ASSERT(false);
-    return;
-  }
-
-  // SuspendThread is asynchronous, so the thread may still be running. Use
-  // GetThreadContext to ensure it's really suspended.
-  // See https://blogs.msdn.microsoft.com/oldnewthing/20150205-00/?p=44743.
-  CONTEXT context;
-  context.ContextFlags = CONTEXT_CONTROL;
-  if (::GetThreadContext(mThreadID, &context)) {
-    FillStackBuffer();
-    FillThreadContext();
-  }
-
-  MOZ_ALWAYS_TRUE(::ResumeThread(mThreadID) != DWORD(-1));
-#endif
-}
-
-void
-ThreadStackHelper::GetNativeStack(Stack& aStack)
-{
-  /*** STUB ***/
-}
-
-#ifdef XP_LINUX
-
-int ThreadStackHelper::sInitialized;
-int ThreadStackHelper::sFillStackSignum;
-
-void
-ThreadStackHelper::FillStackHandler(int aSignal, siginfo_t* aInfo,
-                                    void* aContext)
-{
-  ThreadStackHelper* const helper =
-    reinterpret_cast<ThreadStackHelper*>(aInfo->si_value.sival_ptr);
-  helper->FillStackBuffer();
-  helper->FillThreadContext(aContext);
-  ::sem_post(&helper->mSem);
-}
-
-#endif // XP_LINUX
-
-bool
-ThreadStackHelper::PrepareStackBuffer(Stack& aStack)
-{
-  // Return false to skip getting the stack and return an empty stack
-  aStack.clear();
-  return false;
-}
-
-void
-ThreadStackHelper::FillStackBuffer()
-{
-  MOZ_ASSERT(mStackToFill->empty());
-  /*** STUB ***/
-}
-
-MOZ_ASAN_BLACKLIST void
-ThreadStackHelper::FillThreadContext(void* aContext)
-{
-  /*** STUB ***/
-}
-
-} // namespace mozilla
diff --git a/xpcom/threads/ThreadStackHelper.h b/xpcom/threads/ThreadStackHelper.h
deleted file mode 100644
index 04bcb7b0ab..0000000000
--- a/xpcom/threads/ThreadStackHelper.h
+++ /dev/null
@@ -1,100 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* 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/. */
-
-#ifndef mozilla_ThreadStackHelper_h
-#define mozilla_ThreadStackHelper_h
-
-#include "mozilla/ThreadHangStats.h"
-
-#include "GeckoProfiler.h"
-
-#include <stddef.h>
-
-#if defined(XP_LINUX)
-#include <signal.h>
-#include <semaphore.h>
-#include <sys/types.h>
-#elif defined(XP_WIN)
-#include <windows.h>
-#endif
-
-namespace mozilla {
-
-/**
- * ThreadStackHelper is used to retrieve the profiler pseudo-stack of a
- * thread, as an alternative of using the profiler to take a profile.
- * The target thread first declares an ThreadStackHelper instance;
- * then another thread can call ThreadStackHelper::GetStack to retrieve
- * the pseudo-stack of the target thread at that instant.
- *
- * Only non-copying labels are included in the stack, which means labels
- * with custom text and markers are not included.
- */
-class ThreadStackHelper
-{
-public:
-  typedef Telemetry::HangStack Stack;
-
-private:
-  Stack* mStackToFill;
-
-  bool PrepareStackBuffer(Stack& aStack);
-  void FillStackBuffer();
-  void FillThreadContext(void* aContext = nullptr);
-
-public:
-  /**
-   * Initialize ThreadStackHelper. Must be called from main thread.
-   */
-  static void Startup();
-  /**
-   * Uninitialize ThreadStackHelper. Must be called from main thread.
-   */
-  static void Shutdown();
-
-  /**
-   * Create a ThreadStackHelper instance targeting the current thread.
-   */
-  ThreadStackHelper();
-
-  ~ThreadStackHelper();
-
-  /**
-   * Retrieve the current pseudostack of the thread associated
-   * with this ThreadStackHelper.
-   *
-   * @param aStack Stack instance to be filled.
-   */
-  void GetStack(Stack& aStack);
-
-  /**
-   * Retrieve the current native stack of the thread associated
-   * with this ThreadStackHelper.
-   *
-   * @param aNativeStack Stack instance to be filled.
-   */
-  void GetNativeStack(Stack& aStack);
-
-#if defined(XP_LINUX)
-private:
-  static int sInitialized;
-  static int sFillStackSignum;
-
-  static void FillStackHandler(int aSignal, siginfo_t* aInfo, void* aContext);
-
-  sem_t mSem;
-  pid_t mThreadID;
-
-#elif defined(XP_WIN)
-private:
-  bool mInitialized;
-  HANDLE mThreadID;
-
-#endif
-};
-
-} // namespace mozilla
-
-#endif // mozilla_ThreadStackHelper_h
diff --git a/xpcom/threads/moz.build b/xpcom/threads/moz.build
index 9383400cb6..b09608eba6 100644
--- a/xpcom/threads/moz.build
+++ b/xpcom/threads/moz.build
@@ -62,7 +62,6 @@ UNIFIED_SOURCES += [
     'nsTimerImpl.cpp',
     'SharedThreadPool.cpp',
     'TaskQueue.cpp',
-    'ThreadStackHelper.cpp',
     'ThrottledEventQueue.cpp',
     'TimerThread.cpp',
 ]