Adding upstream version 124.0.1.upstream/124.0.1

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

9 files changed, 1104 insertions, 0 deletions

diff --git a/toolkit/components/terminator/TerminatorTelemetry.sys.mjs b/toolkit/components/terminator/TerminatorTelemetry.sys.mjs
new file mode 100644
index 0000000000..9903027436
--- /dev/null
+++ b/toolkit/components/terminator/TerminatorTelemetry.sys.mjs
@@ -0,0 +1,119 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
+/* 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/. */
+
+/**
+ * Read the data saved by nsTerminator during shutdown and feed it to the
+ * relevant telemetry histograms.
+ */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  setTimeout: "resource://gre/modules/Timer.sys.mjs",
+});
+
+export function nsTerminatorTelemetry() {
+  this._wasNotified = false;
+  this._deferred = Promise.withResolvers();
+
+  IOUtils.sendTelemetry.addBlocker(
+    "TerminatoryTelemetry: Waiting to submit telemetry",
+    this._deferred.promise,
+    () => ({
+      wasNotified: this._wasNotified,
+    })
+  );
+}
+
+var HISTOGRAMS = {
+  "quit-application": "SHUTDOWN_PHASE_DURATION_TICKS_QUIT_APPLICATION",
+  "profile-change-net-teardown":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_CHANGE_NET_TEARDOWN",
+  "profile-change-teardown":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_CHANGE_TEARDOWN",
+  "profile-before-change":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_BEFORE_CHANGE",
+  "profile-before-change-qm":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_BEFORE_CHANGE_QM",
+  "xpcom-will-shutdown": "SHUTDOWN_PHASE_DURATION_TICKS_XPCOM_WILL_SHUTDOWN",
+  "xpcom-shutdown": "SHUTDOWN_PHASE_DURATION_TICKS_XPCOM_SHUTDOWN",
+
+  // The following keys appear in the JSON, but do not have associated
+  // histograms.
+  "xpcom-shutdown-threads": null,
+  XPCOMShutdownFinal: null,
+  CCPostLastCycleCollection: null,
+};
+
+nsTerminatorTelemetry.prototype = {
+  classID: Components.ID("{3f78ada1-cba2-442a-82dd-d5fb300ddea7}"),
+
+  // nsISupports
+
+  QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),
+
+  // nsIObserver
+
+  observe: function DS_observe(aSubject, aTopic, aData) {
+    this._wasNotified = true;
+
+    (async () => {
+      try {
+        //
+        // This data is hardly critical, reading it can wait for a few seconds.
+        //
+        await new Promise(resolve => lazy.setTimeout(resolve, 3000));
+
+        let PATH = PathUtils.join(
+          Services.dirsvc.get("ProfLD", Ci.nsIFile).path,
+          "ShutdownDuration.json"
+        );
+        let data;
+        try {
+          data = await IOUtils.readJSON(PATH);
+        } catch (ex) {
+          if (DOMException.isInstance(ex) && ex.name == "NotFoundError") {
+            return;
+          }
+          // Let other errors be reported by Promise's error-reporting.
+          throw ex;
+        }
+
+        // Clean up
+        await IOUtils.remove(PATH);
+        await IOUtils.remove(PATH + ".tmp");
+
+        for (let k of Object.keys(data)) {
+          let id = HISTOGRAMS[k];
+          if (id === null) {
+            // No histogram associated with this entry.
+            continue;
+          }
+
+          try {
+            let histogram = Services.telemetry.getHistogramById(id);
+            histogram.add(Number.parseInt(data[k]));
+          } catch (ex) {
+            // Make sure that the error is reported and causes test failures,
+            // but otherwise, ignore it.
+            Promise.reject(ex);
+            continue;
+          }
+        }
+
+        // Inform observers that we are done.
+        Services.obs.notifyObservers(
+          null,
+          "shutdown-terminator-telemetry-updated"
+        );
+      } finally {
+        this._deferred.resolve();
+      }
+    })();
+  },
+};
+
+// Module
diff --git a/toolkit/components/terminator/components.conf b/toolkit/components/terminator/components.conf
new file mode 100644
index 0000000000..14c4c2c562
--- /dev/null
+++ b/toolkit/components/terminator/components.conf
@@ -0,0 +1,15 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+Classes = [
+    {
+        'cid': '{3f78ada1-cba2-442a-82dd-d5fb300ddea7}',
+        'contract_ids': ['@mozilla.org/toolkit/shutdown-terminator-telemetry;1'],
+        'esModule': 'resource://gre/modules/TerminatorTelemetry.sys.mjs',
+        'constructor': 'nsTerminatorTelemetry',
+        'categories': {'profile-after-change': 'nsTerminatorTelemetry'},
+    },
+]
diff --git a/toolkit/components/terminator/moz.build b/toolkit/components/terminator/moz.build
new file mode 100644
index 0000000000..f869b86d95
--- /dev/null
+++ b/toolkit/components/terminator/moz.build
@@ -0,0 +1,32 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "Async Tooling")
+
+XPCSHELL_TESTS_MANIFESTS += ["tests/xpcshell/xpcshell.toml"]
+
+SOURCES += [
+    "nsTerminator.cpp",
+]
+
+EXPORTS += [
+    "nsTerminator.h",
+]
+
+EXTRA_COMPONENTS += [
+    "terminator.manifest",
+]
+
+EXTRA_JS_MODULES += [
+    "TerminatorTelemetry.sys.mjs",
+]
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+FINAL_LIBRARY = "xul"
diff --git a/toolkit/components/terminator/nsTerminator.cpp b/toolkit/components/terminator/nsTerminator.cpp
new file mode 100644
index 0000000000..3a8f9f4ba6
--- /dev/null
+++ b/toolkit/components/terminator/nsTerminator.cpp
@@ -0,0 +1,614 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
+ * 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/. */
+
+/**
+ * A watchdog designed to terminate shutdown if it lasts too long.
+ *
+ * This watchdog is designed as a worst-case problem container for the
+ * common case in which Firefox just won't shutdown.
+ *
+ * We spawn a thread during quit-application. If any of the shutdown
+ * steps takes more than n milliseconds (63000 by default), kill the
+ * process as fast as possible, without any cleanup.
+ */
+
+#include "mozilla/ShutdownPhase.h"
+#include "nsTerminator.h"
+
+#include "prthread.h"
+#include "prmon.h"
+#include "prio.h"
+
+#include "nsString.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsAppDirectoryServiceDefs.h"
+
+#include "nsExceptionHandler.h"
+#include "GeckoProfiler.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+#if defined(XP_WIN)
+#  include <windows.h>
+#else
+#  include <unistd.h>
+#endif
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/IntentionalCrash.h"
+#include "mozilla/MemoryChecking.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Telemetry.h"
+
+#include "mozilla/dom/IOUtils.h"
+#include "mozilla/dom/workerinternals/RuntimeService.h"
+
+// Normally, the number of milliseconds that AsyncShutdown waits until
+// it decides to crash is specified as a preference. We use the
+// following value as a fallback if for some reason the preference is
+// absent.
+#define FALLBACK_ASYNCSHUTDOWN_CRASH_AFTER_MS 60000
+
+// Additional number of milliseconds to wait until we decide to exit
+// forcefully.
+#define ADDITIONAL_WAIT_BEFORE_CRASH_MS 3000
+
+#define HEARTBEAT_INTERVAL_MS 100
+
+namespace mozilla {
+
+namespace {
+
+/**
+ * A step during shutdown.
+ *
+ * Shutdown is divided in steps, which all map to an observer
+ * notification. The duration of a step is defined as the number of
+ * ticks between the time we receive a notification and the next one.
+ */
+struct ShutdownStep {
+  mozilla::ShutdownPhase mPhase;
+  Atomic<int> mTicks;
+
+  constexpr explicit ShutdownStep(mozilla::ShutdownPhase aPhase)
+      : mPhase(aPhase), mTicks(-1) {}
+};
+
+static ShutdownStep sShutdownSteps[] = {
+    ShutdownStep(mozilla::ShutdownPhase::AppShutdownConfirmed),
+    ShutdownStep(mozilla::ShutdownPhase::AppShutdownNetTeardown),
+    ShutdownStep(mozilla::ShutdownPhase::AppShutdownTeardown),
+    ShutdownStep(mozilla::ShutdownPhase::AppShutdown),
+    ShutdownStep(mozilla::ShutdownPhase::AppShutdownQM),
+    ShutdownStep(mozilla::ShutdownPhase::XPCOMWillShutdown),
+    ShutdownStep(mozilla::ShutdownPhase::XPCOMShutdown),
+    ShutdownStep(mozilla::ShutdownPhase::XPCOMShutdownThreads),
+    ShutdownStep(mozilla::ShutdownPhase::XPCOMShutdownFinal),
+    ShutdownStep(mozilla::ShutdownPhase::CCPostLastCycleCollection),
+};
+
+int GetStepForPhase(mozilla::ShutdownPhase aPhase) {
+  for (size_t i = 0; i < std::size(sShutdownSteps); i++) {
+    if (sShutdownSteps[i].mPhase >= aPhase) {
+      return (int)i;
+    }
+  }
+  return -1;
+}
+
+// Utility function: create a thread that is non-joinable,
+// does not prevent the process from terminating, is never
+// cooperatively scheduled, and uses a default stack size.
+PRThread* CreateSystemThread(void (*start)(void* arg), void* arg) {
+  PRThread* thread =
+      PR_CreateThread(PR_SYSTEM_THREAD, /* This thread will not prevent the
+                                           process from terminating */
+                      start, arg, PR_PRIORITY_LOW,
+                      PR_GLOBAL_THREAD, /* Make sure that the thread is never
+                                           cooperatively scheduled */
+                      PR_UNJOINABLE_THREAD, 0 /* Use default stack size */
+      );
+  MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(
+      thread);  // This pointer will never be deallocated.
+  return thread;
+}
+
+////////////////////////////////////////////
+//
+// The watchdog
+//
+// This nspr thread is in charge of crashing the process if any stage of
+// shutdown lasts more than some predefined duration. As a side-effect, it
+// measures the duration of each stage of shutdown.
+//
+
+// The heartbeat of the operation.
+//
+// Main thread:
+//
+// * Whenever a shutdown step has been completed, the main thread
+// swaps gHeartbeat to 0 to mark that the shutdown process is still
+// progressing. The value swapped away indicates the number of ticks
+// it took for the shutdown step to advance.
+//
+// Watchdog thread:
+//
+// * Every tick, the watchdog thread increments gHearbeat atomically.
+//
+// A note about precision:
+// Since gHeartbeat is generally reset to 0 between two ticks, this means
+// that gHeartbeat stays at 0 less than one tick. Consequently, values
+// extracted from gHeartbeat must be considered rounded up.
+Atomic<uint32_t> gHeartbeat(0);
+
+struct Options {
+  /**
+   * How many ticks before we should crash the process.
+   */
+  uint32_t crashAfterTicks;
+};
+
+/**
+ * Entry point for the watchdog thread
+ */
+void RunWatchdog(void* arg) {
+  NS_SetCurrentThreadName("Shutdown Hang Terminator");
+
+  // Let's copy and deallocate options, that's one less leak to worry
+  // about.
+  UniquePtr<Options> options((Options*)arg);
+  uint32_t crashAfterTicks = options->crashAfterTicks;
+  options = nullptr;
+
+  const uint32_t timeToLive = crashAfterTicks;
+  while (true) {
+    //
+    // We do not want to sleep for the entire duration,
+    // as putting the computer to sleep would suddenly
+    // cause us to timeout on wakeup.
+    //
+    // Rather, we prefer sleeping for at most 1 second
+    // at a time. If the computer sleeps then wakes up,
+    // we have lost at most one second, which is much
+    // more reasonable.
+    //
+#if defined(XP_WIN)
+    Sleep(HEARTBEAT_INTERVAL_MS /* ms */);
+#else
+    usleep(HEARTBEAT_INTERVAL_MS * 1000 /* usec */);
+#endif
+
+    if (gHeartbeat++ < timeToLive) {
+      continue;
+    }
+
+    // Arrived here we know we will crash in a way or another.
+    NoteIntentionalCrash(XRE_GetProcessTypeString());
+
+    // Until we have general log output for crash annotations in treeherder
+    // (bug 1728721) we manually spit out our nested event loop stack.
+    // XXX: Remove once bug 1728721 is fixed.
+    nsCString stack;
+    AutoNestedEventLoopAnnotation::CopyCurrentStack(stack);
+    printf_stderr(
+        "RunWatchdog: Mainthread nested event loops during hang: \n --- %s\n",
+        stack.get());
+
+    // Let's find the last known shutdown phase.
+    mozilla::ShutdownPhase lastPhase = mozilla::ShutdownPhase::NotInShutdown;
+    // Looping inverse here to make the search more robust in case
+    // the observer that triggers UpdateHeartbeat was not called
+    // at all or in the expected order on some step. This should
+    // give us always the last known ShutdownStep.
+    for (int i = ArrayLength(sShutdownSteps) - 1; i >= 0; --i) {
+      if (sShutdownSteps[i].mTicks > -1) {
+        lastPhase = sShutdownSteps[i].mPhase;
+        break;
+      }
+    }
+
+    if (lastPhase == mozilla::ShutdownPhase::NotInShutdown) {
+      // This is not something we expect to ever happen, but still.
+      CrashReporter::SetMinidumpAnalysisAllThreads();
+      MOZ_CRASH("Shutdown hanging before starting any known phase.");
+    }
+
+    // First check if worker shutdown started and is incomplete, in case
+    // report running workers.
+    mozilla::dom::workerinternals::RuntimeService* runtimeService =
+        mozilla::dom::workerinternals::RuntimeService::GetService();
+    if (runtimeService) {
+      // CrashIfHanging will check if we actually ever asked for worker
+      // shutdown, so calling it before is a no-op.
+      runtimeService->CrashIfHanging();
+    }
+
+    // Otherwise just report our shutdown phase.
+    // This string will be leaked.
+    nsCString msg;
+    msg.AppendPrintf(
+        "Shutdown hanging at step %s. "
+        "Something is blocking the main-thread.",
+        mozilla::AppShutdown::GetShutdownPhaseName(lastPhase));
+
+    CrashReporter::SetMinidumpAnalysisAllThreads();
+    MOZ_CRASH_UNSAFE(strdup(msg.BeginReading()));
+  }
+}
+
+////////////////////////////////////////////
+//
+// Writer thread
+//
+// This nspr thread is in charge of writing to disk statistics produced by the
+// watchdog thread and collected by the main thread. Note that we use a nspr
+// thread rather than usual XPCOM I/O simply because we outlive XPCOM and its
+// threads.
+//
+
+//
+// Communication between the main thread and the writer thread.
+//
+// Main thread:
+//
+// * Whenever a shutdown step has been completed, the main thread
+// obtains the number of ticks from the watchdog threads, builds
+// a string representing all the data gathered so far, places
+// this string in `gWriteData`, and wakes up the writer thread
+// using `gWriteReady`. If `gWriteData` already contained a non-null
+// pointer, this means that the writer thread is lagging behind the
+// main thread, and the main thread cleans up the memory.
+//
+// Writer thread:
+//
+// * When awake, the writer thread swaps `gWriteData` to nullptr. If
+// `gWriteData` contained data to write, the . If so, the writer
+// thread writes the data to a file named "ShutdownDuration.json.tmp",
+// then moves that file to "ShutdownDuration.json" and cleans up the
+// data. If `gWriteData` contains a nullptr, the writer goes to sleep
+// until it is awkened using `gWriteReady`.
+//
+//
+// The data written by the writer thread will be read by another
+// module upon the next restart and fed to Telemetry.
+//
+Atomic<nsCString*> gWriteData(nullptr);
+PRMonitor* gWriteReady = nullptr;
+
+void RunWriter(void* arg) {
+  AUTO_PROFILER_REGISTER_THREAD("Shutdown Statistics Writer");
+  NS_SetCurrentThreadName("Shutdown Statistics Writer");
+
+  MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(arg);
+  // Shutdown will generally complete before we have a chance to
+  // deallocate. This is not a leak.
+
+  // Setup destinationPath and tmpFilePath
+
+  nsCString destinationPath;
+  destinationPath.Adopt(static_cast<char*>(arg));
+  nsAutoCString tmpFilePath;
+  tmpFilePath.Append(destinationPath);
+  tmpFilePath.AppendLiteral(".tmp");
+
+  // Cleanup any file leftover from a previous run
+  Unused << PR_Delete(tmpFilePath.get());
+  Unused << PR_Delete(destinationPath.get());
+
+  while (true) {
+    //
+    // Check whether we have received data from the main thread.
+    //
+    // We perform the check before waiting on `gWriteReady` as we may
+    // have received data while we were busy writing.
+    //
+    // Also note that gWriteData may have been modified several times
+    // since we last checked. That's ok, we are not losing any important
+    // data (since we keep adding data), and we are not leaking memory
+    // (since the main thread deallocates any data that hasn't been
+    // consumed by the writer thread).
+    //
+    UniquePtr<nsCString> data(gWriteData.exchange(nullptr));
+    if (!data) {
+      // Data is not available yet.
+      // Wait until the main thread provides it.
+      PR_EnterMonitor(gWriteReady);
+      PR_Wait(gWriteReady, PR_INTERVAL_NO_TIMEOUT);
+      PR_ExitMonitor(gWriteReady);
+      continue;
+    }
+
+    MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(data.get());
+    // Shutdown may complete before we have a chance to deallocate.
+    // This is not a leak.
+
+    //
+    // Write to a temporary file
+    //
+    // In case of any error, we simply give up. Since the data is
+    // hardly critical, we don't want to spend too much effort
+    // salvaging it.
+    //
+    UniquePtr<PRFileDesc, PR_CloseDelete> tmpFileDesc(PR_Open(
+        tmpFilePath.get(), PR_WRONLY | PR_TRUNCATE | PR_CREATE_FILE, 00600));
+
+    // Shutdown may complete before we have a chance to close the file.
+    // This is not a leak.
+    MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(tmpFileDesc.get());
+
+    if (tmpFileDesc == nullptr) {
+      break;
+    }
+    if (PR_Write(tmpFileDesc.get(), data->get(), data->Length()) == -1) {
+      break;
+    }
+    tmpFileDesc.reset();
+
+    //
+    // Rename on top of destination file.
+    //
+    // This is not sufficient to guarantee that the destination file
+    // will be written correctly, but, again, we don't care enough
+    // about the data to make more efforts.
+    //
+    Unused << PR_Delete(destinationPath.get());
+    if (PR_Rename(tmpFilePath.get(), destinationPath.get()) != PR_SUCCESS) {
+      break;
+    }
+  }
+}
+
+}  // namespace
+
+NS_IMPL_ISUPPORTS(nsTerminator, nsIObserver)
+
+nsTerminator::nsTerminator() : mInitialized(false), mCurrentStep(-1) {}
+
+// Actually launch these threads. This takes place at the first sign of
+// shutdown.
+void nsTerminator::Start() {
+  MOZ_ASSERT(!mInitialized);
+
+  StartWatchdog();
+#if !defined(NS_FREE_PERMANENT_DATA)
+  // Only allow nsTerminator to write on non-leak-checked builds so we don't
+  // get leak warnings on shutdown for intentional leaks (see bug 1242084).
+  // This will be enabled again by bug 1255484 when 1255478 lands.
+  StartWriter();
+#endif  // !defined(NS_FREE_PERMANENT_DATA)
+  mInitialized = true;
+}
+
+NS_IMETHODIMP
+nsTerminator::Observe(nsISupports*, const char* aTopic, const char16_t*) {
+  // This Observe is now only used for testing purposes.
+  // XXX: Check if we should change our testing strategy.
+  if (strcmp(aTopic, "terminator-test-quit-application") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::AppShutdownConfirmed);
+  } else if (strcmp(aTopic, "terminator-test-profile-change-net-teardown") ==
+             0) {
+    AdvancePhase(mozilla::ShutdownPhase::AppShutdownNetTeardown);
+  } else if (strcmp(aTopic, "terminator-test-profile-change-teardown") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::AppShutdownTeardown);
+  } else if (strcmp(aTopic, "terminator-test-profile-before-change") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::AppShutdown);
+  } else if (strcmp(aTopic, "terminator-test-profile-before-change-qm") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::AppShutdownQM);
+  } else if (strcmp(aTopic,
+                    "terminator-test-profile-before-change-telemetry") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::AppShutdownTelemetry);
+  } else if (strcmp(aTopic, "terminator-test-xpcom-will-shutdown") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::XPCOMWillShutdown);
+  } else if (strcmp(aTopic, "terminator-test-xpcom-shutdown") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::XPCOMShutdown);
+  } else if (strcmp(aTopic, "terminator-test-xpcom-shutdown-threads") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::XPCOMShutdownThreads);
+  } else if (strcmp(aTopic, "terminator-test-XPCOMShutdownFinal") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::XPCOMShutdownFinal);
+  } else if (strcmp(aTopic, "terminator-test-CCPostLastCycleCollection") == 0) {
+    AdvancePhase(mozilla::ShutdownPhase::CCPostLastCycleCollection);
+  }
+
+  return NS_OK;
+}
+
+// Prepare, allocate and start the watchdog thread.
+// By design, it will never finish, nor be deallocated.
+void nsTerminator::StartWatchdog() {
+  int32_t crashAfterMS =
+      Preferences::GetInt("toolkit.asyncshutdown.crash_timeout",
+                          FALLBACK_ASYNCSHUTDOWN_CRASH_AFTER_MS);
+  // Ignore negative values
+  if (crashAfterMS <= 0) {
+    crashAfterMS = FALLBACK_ASYNCSHUTDOWN_CRASH_AFTER_MS;
+  }
+
+  // Add a little padding, to ensure that we do not crash before
+  // AsyncShutdown.
+  if (crashAfterMS > INT32_MAX - ADDITIONAL_WAIT_BEFORE_CRASH_MS) {
+    // Defend against overflow
+    crashAfterMS = INT32_MAX;
+  } else {
+    crashAfterMS += ADDITIONAL_WAIT_BEFORE_CRASH_MS;
+  }
+
+#ifdef MOZ_VALGRIND
+  // If we're running on Valgrind, we'll be making forward progress at a
+  // rate of somewhere between 1/25th and 1/50th of normal.  This can cause
+  // timeouts frequently enough to be a problem for the Valgrind runs on
+  // automation: see bug 1296819.  As an attempt to avoid the worst of this,
+  // scale up the presented timeout by a factor of three.  For a
+  // non-Valgrind-enabled build, or for an enabled build which isn't running
+  // on Valgrind, the timeout is unchanged.
+  if (RUNNING_ON_VALGRIND) {
+    const int32_t scaleUp = 3;
+    if (crashAfterMS >= (INT32_MAX / scaleUp) - 1) {
+      // Defend against overflow
+      crashAfterMS = INT32_MAX;
+    } else {
+      crashAfterMS *= scaleUp;
+    }
+  }
+#endif
+
+  UniquePtr<Options> options(new Options());
+  // crashAfterTicks is guaranteed to be > 0 as
+  // crashAfterMS >= ADDITIONAL_WAIT_BEFORE_CRASH_MS >> HEARTBEAT_INTERVAL_MS
+  options->crashAfterTicks = crashAfterMS / HEARTBEAT_INTERVAL_MS;
+
+  DebugOnly<PRThread*> watchdogThread =
+      CreateSystemThread(RunWatchdog, options.release());
+  MOZ_ASSERT(watchdogThread);
+}
+
+// Prepare, allocate and start the writer thread. By design, it will never
+// finish, nor be deallocated. In case of error, we degrade
+// gracefully to not writing Telemetry data.
+void nsTerminator::StartWriter() {
+  if (!Telemetry::CanRecordExtended()) {
+    return;
+  }
+  nsCOMPtr<nsIFile> profLD;
+  nsresult rv = NS_GetSpecialDirectory(NS_APP_USER_PROFILE_LOCAL_50_DIR,
+                                       getter_AddRefs(profLD));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  rv = profLD->Append(u"ShutdownDuration.json"_ns);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  nsAutoString path;
+  rv = profLD->GetPath(path);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  gWriteReady = PR_NewMonitor();
+  MOZ_LSAN_INTENTIONALLY_LEAK_OBJECT(
+      gWriteReady);  // We will never deallocate this object
+  PRThread* writerThread = CreateSystemThread(RunWriter, ToNewUTF8String(path));
+
+  if (!writerThread) {
+    return;
+  }
+}
+
+// This helper is here to preserve the existing crash reporting behavior
+// based on observer topic names, using the shutdown phase name only for
+// phases without associated topic.
+const char* GetReadableNameForPhase(mozilla::ShutdownPhase aPhase) {
+  const char* readableName = mozilla::AppShutdown::GetObserverKey(aPhase);
+  if (!readableName) {
+    readableName = mozilla::AppShutdown::GetShutdownPhaseName(aPhase);
+  }
+  return readableName;
+}
+
+void nsTerminator::AdvancePhase(mozilla::ShutdownPhase aPhase) {
+  // If the phase is unknown, just ignore it.
+  auto step = GetStepForPhase(aPhase);
+  if (step < 0) {
+    return;
+  }
+
+  // As we have seen examples in the wild of shutdown notifications
+  // not being sent (or not being sent in the expected order), we do
+  // not assume a specific order.
+  if (!mInitialized) {
+    Start();
+  }
+
+  UpdateHeartbeat(step);
+#if !defined(NS_FREE_PERMANENT_DATA)
+  // Only allow nsTerminator to write on non-leak checked builds so we don't get
+  // leak warnings on shutdown for intentional leaks (see bug 1242084). This
+  // will be enabled again by bug 1255484 when 1255478 lands.
+  UpdateTelemetry();
+#endif  // !defined(NS_FREE_PERMANENT_DATA)
+  UpdateCrashReport(GetReadableNameForPhase(aPhase));
+}
+
+void nsTerminator::UpdateHeartbeat(int32_t aStep) {
+  MOZ_ASSERT(aStep >= mCurrentStep);
+
+  if (aStep > mCurrentStep) {
+    // Reset the clock, find out how long the current phase has lasted.
+    uint32_t ticks = gHeartbeat.exchange(0);
+    if (mCurrentStep >= 0) {
+      sShutdownSteps[mCurrentStep].mTicks = ticks;
+    }
+    sShutdownSteps[aStep].mTicks = 0;
+
+    mCurrentStep = aStep;
+  }
+}
+
+void nsTerminator::UpdateTelemetry() {
+  if (!Telemetry::CanRecordExtended() || !gWriteReady) {
+    return;
+  }
+
+  //
+  // We need Telemetry data on the effective duration of each step,
+  // to be able to tune the time-to-crash of each of both the
+  // Terminator and AsyncShutdown. However, at this stage, it is too
+  // late to record such data into Telemetry, so we write it to disk
+  // and read it upon the next startup.
+  //
+
+  // Build JSON.
+  UniquePtr<nsCString> telemetryData(new nsCString());
+  telemetryData->AppendLiteral("{");
+  size_t fields = 0;
+  for (auto& shutdownStep : sShutdownSteps) {
+    if (shutdownStep.mTicks < 0) {
+      // Ignore this field.
+      continue;
+    }
+    if (fields++ > 0) {
+      telemetryData->AppendLiteral(", ");
+    }
+    telemetryData->AppendLiteral(R"(")");
+    telemetryData->Append(GetReadableNameForPhase(shutdownStep.mPhase));
+    telemetryData->AppendLiteral(R"(": )");
+    telemetryData->AppendInt(shutdownStep.mTicks);
+  }
+  telemetryData->AppendLiteral("}");
+
+  if (fields == 0) {
+    // Nothing to write
+    return;
+  }
+
+  //
+  // Send data to the worker thread.
+  //
+  delete gWriteData.exchange(
+      telemetryData.release());  // Clear any data that hasn't been written yet
+
+  // In case the worker thread was sleeping, wake it up.
+  PR_EnterMonitor(gWriteReady);
+  PR_Notify(gWriteReady);
+  PR_ExitMonitor(gWriteReady);
+}
+
+void nsTerminator::UpdateCrashReport(const char* aTopic) {
+  // In case of crash, we wish to know where in shutdown we are
+  nsAutoCString report(aTopic);
+
+  Unused << CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::ShutdownProgress, report);
+}
+}  // namespace mozilla
diff --git a/toolkit/components/terminator/nsTerminator.h b/toolkit/components/terminator/nsTerminator.h
new file mode 100644
index 0000000000..46c3e17b92
--- /dev/null
+++ b/toolkit/components/terminator/nsTerminator.h
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
+ * 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 nsTerminator_h__
+#define nsTerminator_h__
+
+#include "nsISupports.h"
+#include "nsIObserver.h"
+
+namespace mozilla {
+
+class nsTerminator final : public nsIObserver {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+
+  nsTerminator();
+  void AdvancePhase(mozilla::ShutdownPhase aPhase);
+
+ private:
+  void Start();
+  void StartWatchdog();
+  void StartWriter();
+
+  void UpdateHeartbeat(int aStep);
+  void UpdateTelemetry();
+  void UpdateCrashReport(const char* aTopic);
+
+  ~nsTerminator() = default;
+
+  bool mInitialized;
+  int mCurrentStep;
+};
+
+}  // namespace mozilla
+
+#define NS_TOOLKIT_TERMINATOR_CID                    \
+  {                                                  \
+    0x2e59cc70, 0xf83a, 0x412f, {                    \
+      0x89, 0xd4, 0x45, 0x38, 0x85, 0x83, 0x72, 0x17 \
+    }                                                \
+  }
+#define NS_TOOLKIT_TERMINATOR_CONTRACTID \
+  "@mozilla.org/toolkit/shutdown-terminator;1"
+
+#endif  // nsTerminator_h__
diff --git a/toolkit/components/terminator/terminator.manifest b/toolkit/components/terminator/terminator.manifest
new file mode 100644
index 0000000000..33cb143de9
--- /dev/null
+++ b/toolkit/components/terminator/terminator.manifest
@@ -0,0 +1 @@
+category profile-after-change nsTerminator @mozilla.org/toolkit/shutdown-terminator;1
diff --git a/toolkit/components/terminator/tests/xpcshell/test_terminator_record.js b/toolkit/components/terminator/tests/xpcshell/test_terminator_record.js
new file mode 100644
index 0000000000..62cee636f3
--- /dev/null
+++ b/toolkit/components/terminator/tests/xpcshell/test_terminator_record.js
@@ -0,0 +1,171 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+"use strict";
+
+// Test that the Shutdown Terminator records durations correctly
+
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+var PATH;
+var PATH_TMP;
+var terminator;
+
+var HEARTBEAT_MS = 100;
+
+let KEYS = [
+  "quit-application",
+  "profile-change-net-teardown",
+  "profile-change-teardown",
+  "profile-before-change",
+  "profile-before-change-qm",
+  "xpcom-will-shutdown",
+  "xpcom-shutdown",
+  "xpcom-shutdown-threads",
+  "XPCOMShutdownFinal",
+  "CCPostLastCycleCollection",
+];
+
+let DATA = [];
+let MeasuredDurations = [];
+
+add_task(async function init() {
+  do_get_profile();
+  PATH = PathUtils.join(PathUtils.localProfileDir, "ShutdownDuration.json");
+  PATH_TMP = PATH + ".tmp";
+
+  // Initialize the terminator
+  // (normally, this is done through the manifest file, but xpcshell
+  // doesn't take them into account).
+  info("Initializing the Terminator");
+  terminator = Cc["@mozilla.org/toolkit/shutdown-terminator;1"].createInstance(
+    Ci.nsIObserver
+  );
+});
+
+var promiseShutdownDurationData = async function () {
+  // Wait until PATH exists.
+  // Timeout if it is never created.
+  while (true) {
+    if (await IOUtils.exists(PATH)) {
+      break;
+    }
+
+    // Wait just a very short period to not increase measured values.
+    // Usually the file should appear almost immediately.
+    await new Promise(resolve => setTimeout(resolve, 50));
+  }
+
+  return IOUtils.readJSON(PATH);
+};
+
+var currentPhase = 0;
+
+var advancePhase = async function () {
+  let key = "terminator-test-" + KEYS[currentPhase];
+  let msDuration = 200 + HEARTBEAT_MS * currentPhase;
+
+  info("Advancing shutdown phase to " + KEYS[currentPhase]);
+  terminator.observe(null, key, null);
+  await new Promise(resolve => setTimeout(resolve, msDuration));
+
+  let data = await promiseShutdownDurationData();
+
+  Assert.ok(KEYS[currentPhase] in data, "The file contains the expected key");
+  Assert.equal(
+    Object.keys(data).length,
+    currentPhase + 1,
+    "File does not contain more durations than expected"
+  );
+
+  DATA[currentPhase] = data;
+  currentPhase++;
+  if (currentPhase < KEYS.length) {
+    return true;
+  }
+  return false;
+};
+
+// This is a timing affected test, as we want to check if the time measurements
+// from the terminator are reasonable. Bug 1768795 assumes that they tend to
+// be lower than wall-clock, in particular on MacOS, confirmed by the logs on
+// intermittent bug 1760094. This is not a big deal for the terminator's
+// general functionality (timeouts might just come a little later than
+// expected nominally), but it makes testing harder and the transferred
+// telemetry data slightly less reliable (shutdowns might appear shorter than
+// they really were). So this test is just happy if there is any data that
+// is not too long wrt what we expect. If we ever want to fix bug 1768795,
+// we can check for a more reasonable lower boundary, too.
+add_task(async function test_record() {
+  info("Collecting duration data for all known phases");
+
+  let morePhases = true;
+  while (morePhases) {
+    let beforeWait = Date.now();
+
+    morePhases = await advancePhase();
+
+    await IOUtils.remove(PATH);
+    await IOUtils.remove(PATH_TMP);
+
+    // We measure the effective time that passed as wall-clock and include all
+    // file IO overhead as the terminator will do so in its measurement, too.
+    MeasuredDurations[currentPhase - 1] = Math.floor(
+      (Date.now() - beforeWait) / HEARTBEAT_MS
+    );
+  }
+
+  Assert.equal(DATA.length, KEYS.length, "We have data for each phase");
+
+  for (let i = 0; i < KEYS.length; i++) {
+    let lastDuration = DATA[KEYS.length - 1][KEYS[i]];
+    Assert.equal(
+      typeof lastDuration,
+      "number",
+      "Duration of phase " + i + ":" + KEYS[i] + " is a number"
+    );
+
+    // The durations are only meaningful after we advanced to the next phase.
+    if (i < KEYS.length - 1) {
+      // So we read it from the data written for the following phase.
+      let ticksDuration = DATA[i + 1][KEYS[i]];
+      let measuredDuration = MeasuredDurations[i];
+      info(
+        "measuredDuration:" + measuredDuration + " - " + typeof measuredDuration
+      );
+      Assert.lessOrEqual(
+        ticksDuration,
+        measuredDuration + 2,
+        "Duration of phase " + i + ":" + KEYS[i] + " is not too long"
+      );
+      Assert.greaterOrEqual(
+        ticksDuration,
+        0, // TODO: Raise the lower boundary after bug 1768795.
+        "Duration of phase " + i + ":" + KEYS[i] + " is not too short"
+      );
+    }
+    // This check is done only for phases <= xpcom-shutdown-threads
+    // where we have two data points.
+    if (i < KEYS.length - 2) {
+      let ticksDuration = DATA[i + 1][KEYS[i]];
+      Assert.equal(
+        ticksDuration,
+        DATA[KEYS.length - 1][KEYS[i]],
+        "Duration of phase " + i + ":" + KEYS[i] + " hasn't changed"
+      );
+    }
+  }
+
+  // Note that after this check the KEYS array remains sorted, so this
+  // must be the last check to not get confused.
+  Assert.equal(
+    Object.keys(DATA[KEYS.length - 1])
+      .sort()
+      .join(", "),
+    KEYS.sort().join(", "),
+    "The last file contains all expected keys"
+  );
+});
diff --git a/toolkit/components/terminator/tests/xpcshell/test_terminator_reload.js b/toolkit/components/terminator/tests/xpcshell/test_terminator_reload.js
new file mode 100644
index 0000000000..79aecd818b
--- /dev/null
+++ b/toolkit/components/terminator/tests/xpcshell/test_terminator_reload.js
@@ -0,0 +1,88 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test that the Shutdown Terminator reloads durations correctly
+
+const HISTOGRAMS = {
+  "quit-application": "SHUTDOWN_PHASE_DURATION_TICKS_QUIT_APPLICATION",
+  "profile-change-net-teardown":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_CHANGE_NET_TEARDOWN",
+  "profile-change-teardown":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_CHANGE_TEARDOWN",
+  "profile-before-change":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_BEFORE_CHANGE",
+  "profile-before-change-qm":
+    "SHUTDOWN_PHASE_DURATION_TICKS_PROFILE_BEFORE_CHANGE_QM",
+  "xpcom-will-shutdown": "SHUTDOWN_PHASE_DURATION_TICKS_XPCOM_WILL_SHUTDOWN",
+  "xpcom-shutdown": "SHUTDOWN_PHASE_DURATION_TICKS_XPCOM_SHUTDOWN",
+};
+
+let PATH;
+
+add_setup(async function init() {
+  do_get_profile();
+  PATH = PathUtils.join(PathUtils.localProfileDir, "ShutdownDuration.json");
+});
+
+add_task(async function test_reload() {
+  info("Forging data");
+  let data = {};
+  let telemetrySnapshots = Services.telemetry.getSnapshotForHistograms(
+    "main",
+    false /* clear */
+  ).parent;
+  let i = 0;
+  for (let k of Object.keys(HISTOGRAMS)) {
+    let id = HISTOGRAMS[k];
+    data[k] = i++;
+    Assert.equal(
+      telemetrySnapshots[id] || undefined,
+      undefined,
+      "Histogram " + id + " is empty"
+    );
+  }
+
+  // Extra fields that nsTerminator reports that we do not have histograms for.
+  data["xpcom-shutdown-threads"] = 123;
+  data.XPCOMShutdownFinal = 456;
+  data.CCPostLastCycleCollection = 789;
+
+  await IOUtils.writeJSON(PATH, data);
+
+  const TOPIC = "shutdown-terminator-telemetry-updated";
+
+  let wait = new Promise(resolve =>
+    Services.obs.addObserver(function observer() {
+      info("Telemetry has been updated");
+      Services.obs.removeObserver(observer, TOPIC);
+      resolve();
+    }, TOPIC)
+  );
+
+  info("Starting nsTerminatorTelemetry");
+  let tt = Cc[
+    "@mozilla.org/toolkit/shutdown-terminator-telemetry;1"
+  ].createInstance(Ci.nsIObserver);
+  tt.observe(null, "profile-after-change", "");
+
+  info("Waiting until telemetry is updated");
+  // Now wait until Telemetry is updated
+  await wait;
+
+  telemetrySnapshots = Services.telemetry.getSnapshotForHistograms(
+    "main",
+    false /* clear */
+  ).parent;
+  for (let k of Object.keys(HISTOGRAMS)) {
+    let id = HISTOGRAMS[k];
+    info("Testing histogram " + id);
+    let snapshot = telemetrySnapshots[id];
+    let count = 0;
+    for (let x of Object.values(snapshot.values)) {
+      count += x;
+    }
+    Assert.equal(count, 1, "We have added one item");
+  }
+});
diff --git a/toolkit/components/terminator/tests/xpcshell/xpcshell.toml b/toolkit/components/terminator/tests/xpcshell/xpcshell.toml
new file mode 100644
index 0000000000..cb328ca2c8
--- /dev/null
+++ b/toolkit/components/terminator/tests/xpcshell/xpcshell.toml
@@ -0,0 +1,15 @@
+[DEFAULT]
+head = ""
+
+["test_terminator_record.js"]
+skip-if = [
+    "debug",
+    "asan", # Disabled by bug 1242084, bug 1255484 will enable it again
+    "ccov", # Bug 1607583 tracks the ccov failure
+    "tsan", # Bug 1683730 made this timeout for tsan.
+]
+run-sequentially = "very high failure rate in parallel"
+
+["test_terminator_reload.js"]
+skip-if = ["os == 'android'"]
+run-sequentially = "very high failure rate in parallel"