1 files changed, 434 insertions, 0 deletions
diff --git a/xpcom/threads/HangMonitor.cpp b/xpcom/threads/HangMonitor.cpp
new file mode 100644
index 000000000..71cc67ca4
--- /dev/null
+++ b/xpcom/threads/HangMonitor.cpp
@@ -0,0 +1,434 @@
+/* -*- 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 "mozilla/HangMonitor.h"
+
+#include "mozilla/Atomics.h"
+#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"
+#include "mozilla/StackWalk.h"
+#ifdef _WIN64
+#include "mozilla/StackWalk_windows.h"
+#endif
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+
+#ifdef MOZ_CRASHREPORTER
+#include "nsExceptionHandler.h"
+#endif
+
+#ifdef XP_WIN
+#include <windows.h>
+#endif
+
+#if defined(MOZ_ENABLE_PROFILER_SPS) && defined(MOZ_PROFILING) && defined(XP_WIN)
+  #define REPORT_CHROME_HANGS
+#endif
+
+namespace mozilla {
+namespace HangMonitor {
+
+/**
+ * A flag which may be set from within a debugger to disable the hang
+ * monitor.
+ */
+volatile bool gDebugDisableHangMonitor = false;
+
+const char kHangMonitorPrefName[] = "hangmonitor.timeout";
+
+#ifdef REPORT_CHROME_HANGS
+const char kTelemetryPrefName[] = "toolkit.telemetry.enabled";
+#endif
+
+// Monitor protects gShutdown and gTimeout, but not gTimestamp which rely on
+// being atomically set by the processor; synchronization doesn't really matter
+// in this use case.
+Monitor* gMonitor;
+
+// The timeout preference, in seconds.
+int32_t gTimeout;
+
+PRThread* gThread;
+
+// Set when shutdown begins to signal the thread to exit immediately.
+bool gShutdown;
+
+// The timestamp of the last event notification, or PR_INTERVAL_NO_WAIT if
+// we're currently not processing events.
+Atomic<PRIntervalTime> gTimestamp(PR_INTERVAL_NO_WAIT);
+
+#ifdef REPORT_CHROME_HANGS
+// Main thread ID used in reporting chrome hangs under Windows
+static HANDLE winMainThreadHandle = nullptr;
+
+// Default timeout for reporting chrome hangs to Telemetry (5 seconds)
+static const int32_t DEFAULT_CHROME_HANG_INTERVAL = 5;
+
+// Maximum number of PCs to gather from the stack
+static const int32_t MAX_CALL_STACK_PCS = 400;
+#endif
+
+// PrefChangedFunc
+void
+PrefChanged(const char*, void*)
+{
+  int32_t newval = Preferences::GetInt(kHangMonitorPrefName);
+#ifdef REPORT_CHROME_HANGS
+  // Monitor chrome hangs on the profiling branch if Telemetry enabled
+  if (newval == 0) {
+    bool telemetryEnabled = Preferences::GetBool(kTelemetryPrefName);
+    if (telemetryEnabled) {
+      newval = DEFAULT_CHROME_HANG_INTERVAL;
+    }
+  }
+#endif
+  MonitorAutoLock lock(*gMonitor);
+  if (newval != gTimeout) {
+    gTimeout = newval;
+    lock.Notify();
+  }
+}
+
+void
+Crash()
+{
+  if (gDebugDisableHangMonitor) {
+    return;
+  }
+
+#ifdef XP_WIN
+  if (::IsDebuggerPresent()) {
+    return;
+  }
+#endif
+
+#ifdef MOZ_CRASHREPORTER
+  // If you change this, you must also deal with the threadsafety of AnnotateCrashReport in
+  // non-chrome processes!
+  if (GeckoProcessType_Default == XRE_GetProcessType()) {
+    CrashReporter::AnnotateCrashReport(NS_LITERAL_CSTRING("Hang"),
+                                       NS_LITERAL_CSTRING("1"));
+  }
+#endif
+
+  NS_RUNTIMEABORT("HangMonitor triggered");
+}
+
+#ifdef REPORT_CHROME_HANGS
+
+static void
+ChromeStackWalker(uint32_t aFrameNumber, void* aPC, void* aSP, void* aClosure)
+{
+  MOZ_ASSERT(aClosure);
+  std::vector<uintptr_t>* stack =
+    static_cast<std::vector<uintptr_t>*>(aClosure);
+  if (stack->size() == MAX_CALL_STACK_PCS) {
+    return;
+  }
+  MOZ_ASSERT(stack->size() < MAX_CALL_STACK_PCS);
+  stack->push_back(reinterpret_cast<uintptr_t>(aPC));
+}
+
+static void
+GetChromeHangReport(Telemetry::ProcessedStack& aStack,
+                    int32_t& aSystemUptime,
+                    int32_t& aFirefoxUptime)
+{
+  MOZ_ASSERT(winMainThreadHandle);
+
+  // The thread we're about to suspend might have the alloc lock
+  // so allocate ahead of time
+  std::vector<uintptr_t> rawStack;
+  rawStack.reserve(MAX_CALL_STACK_PCS);
+
+  // Workaround possible deadlock where the main thread is running a
+  // long-standing JS job, and happens to be in the JIT allocator when we
+  // suspend it. Since, on win 64, this requires holding a process lock that
+  // MozStackWalk requires, take this "workaround lock" to avoid deadlock.
+#ifdef _WIN64
+  AcquireStackWalkWorkaroundLock();
+#endif
+  DWORD ret = ::SuspendThread(winMainThreadHandle);
+  bool suspended = false;
+  if (ret != -1) {
+    // 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(winMainThreadHandle, &context)) {
+      suspended = true;
+    }
+  }
+
+#ifdef _WIN64
+  ReleaseStackWalkWorkaroundLock();
+#endif
+
+  if (!suspended) {
+    if (ret != -1) {
+      MOZ_ALWAYS_TRUE(::ResumeThread(winMainThreadHandle) != DWORD(-1));
+    }
+    return;
+  }
+
+  MozStackWalk(ChromeStackWalker, /* skipFrames */ 0, /* maxFrames */ 0,
+               reinterpret_cast<void*>(&rawStack),
+               reinterpret_cast<uintptr_t>(winMainThreadHandle), nullptr);
+  ret = ::ResumeThread(winMainThreadHandle);
+  if (ret == -1) {
+    return;
+  }
+  aStack = Telemetry::GetStackAndModules(rawStack);
+
+  // Record system uptime (in minutes) at the time of the hang
+  aSystemUptime = ((GetTickCount() / 1000) - (gTimeout * 2)) / 60;
+
+  // Record Firefox uptime (in minutes) at the time of the hang
+  bool error;
+  TimeStamp processCreation = TimeStamp::ProcessCreation(error);
+  if (!error) {
+    TimeDuration td = TimeStamp::Now() - processCreation;
+    aFirefoxUptime = (static_cast<int32_t>(td.ToSeconds()) - (gTimeout * 2)) / 60;
+  } else {
+    aFirefoxUptime = -1;
+  }
+}
+
+#endif
+
+void
+ThreadMain(void*)
+{
+  PR_SetCurrentThreadName("Hang Monitor");
+
+  MonitorAutoLock lock(*gMonitor);
+
+  // In order to avoid issues with the hang monitor incorrectly triggering
+  // during a general system stop such as sleeping, the monitor thread must
+  // run twice to trigger hang protection.
+  PRIntervalTime lastTimestamp = 0;
+  int waitCount = 0;
+
+#ifdef REPORT_CHROME_HANGS
+  Telemetry::ProcessedStack stack;
+  int32_t systemUptime = -1;
+  int32_t firefoxUptime = -1;
+  UniquePtr<HangAnnotations> annotations;
+#endif
+
+  while (true) {
+    if (gShutdown) {
+      return; // Exit the thread
+    }
+
+    // avoid rereading the volatile value in this loop
+    PRIntervalTime timestamp = gTimestamp;
+
+    PRIntervalTime now = PR_IntervalNow();
+
+    if (timestamp != PR_INTERVAL_NO_WAIT &&
+        now < timestamp) {
+      // 32-bit overflow, reset for another waiting period
+      timestamp = 1; // lowest legal PRInterval value
+    }
+
+    if (timestamp != PR_INTERVAL_NO_WAIT &&
+        timestamp == lastTimestamp &&
+        gTimeout > 0) {
+      ++waitCount;
+#ifdef REPORT_CHROME_HANGS
+      // Capture the chrome-hang stack + Firefox & system uptimes after
+      // the minimum hang duration has been reached (not when the hang ends)
+      if (waitCount == 2) {
+        GetChromeHangReport(stack, systemUptime, firefoxUptime);
+        annotations = ChromeHangAnnotatorCallout();
+      }
+#else
+      // This is the crash-on-hang feature.
+      // See bug 867313 for the quirk in the waitCount comparison
+      if (waitCount >= 2) {
+        int32_t delay =
+          int32_t(PR_IntervalToSeconds(now - timestamp));
+        if (delay >= gTimeout) {
+          MonitorAutoUnlock unlock(*gMonitor);
+          Crash();
+        }
+      }
+#endif
+    } else {
+#ifdef REPORT_CHROME_HANGS
+      if (waitCount >= 2) {
+        uint32_t hangDuration = PR_IntervalToSeconds(now - lastTimestamp);
+        Telemetry::RecordChromeHang(hangDuration, stack, systemUptime,
+                                    firefoxUptime, Move(annotations));
+        stack.Clear();
+      }
+#endif
+      lastTimestamp = timestamp;
+      waitCount = 0;
+    }
+
+    PRIntervalTime timeout;
+    if (gTimeout <= 0) {
+      timeout = PR_INTERVAL_NO_TIMEOUT;
+    } else {
+      timeout = PR_MillisecondsToInterval(gTimeout * 500);
+    }
+    lock.Wait(timeout);
+  }
+}
+
+void
+Startup()
+{
+  if (GeckoProcessType_Default != XRE_GetProcessType() &&
+      GeckoProcessType_Content != XRE_GetProcessType()) {
+    return;
+  }
+
+  MOZ_ASSERT(!gMonitor, "Hang monitor already initialized");
+  gMonitor = new Monitor("HangMonitor");
+
+  Preferences::RegisterCallback(PrefChanged, kHangMonitorPrefName, nullptr);
+  PrefChanged(nullptr, nullptr);
+
+#ifdef REPORT_CHROME_HANGS
+  Preferences::RegisterCallback(PrefChanged, kTelemetryPrefName, nullptr);
+  winMainThreadHandle =
+    OpenThread(THREAD_ALL_ACCESS, FALSE, GetCurrentThreadId());
+  if (!winMainThreadHandle) {
+    return;
+  }
+#endif
+
+  // Don't actually start measuring hangs until we hit the main event loop.
+  // This potentially misses a small class of really early startup hangs,
+  // but avoids dealing with some xpcshell tests and other situations which
+  // start XPCOM but don't ever start the event loop.
+  Suspend();
+
+  gThread = PR_CreateThread(PR_USER_THREAD,
+                            ThreadMain,
+                            nullptr, PR_PRIORITY_LOW, PR_GLOBAL_THREAD,
+                            PR_JOINABLE_THREAD, 0);
+}
+
+void
+Shutdown()
+{
+  if (GeckoProcessType_Default != XRE_GetProcessType() &&
+      GeckoProcessType_Content != XRE_GetProcessType()) {
+    return;
+  }
+
+  MOZ_ASSERT(gMonitor, "Hang monitor not started");
+
+  {
+    // Scope the lock we're going to delete later
+    MonitorAutoLock lock(*gMonitor);
+    gShutdown = true;
+    lock.Notify();
+  }
+
+  // thread creation could theoretically fail
+  if (gThread) {
+    PR_JoinThread(gThread);
+    gThread = nullptr;
+  }
+
+  delete gMonitor;
+  gMonitor = nullptr;
+}
+
+static bool
+IsUIMessageWaiting()
+{
+#ifndef XP_WIN
+  return false;
+#else
+#define NS_WM_IMEFIRST WM_IME_SETCONTEXT
+#define NS_WM_IMELAST  WM_IME_KEYUP
+  BOOL haveUIMessageWaiting = FALSE;
+  MSG msg;
+  haveUIMessageWaiting |= ::PeekMessageW(&msg, nullptr, WM_KEYFIRST,
+                                         WM_IME_KEYLAST, PM_NOREMOVE);
+  haveUIMessageWaiting |= ::PeekMessageW(&msg, nullptr, NS_WM_IMEFIRST,
+                                         NS_WM_IMELAST, PM_NOREMOVE);
+  haveUIMessageWaiting |= ::PeekMessageW(&msg, nullptr, WM_MOUSEFIRST,
+                                         WM_MOUSELAST, PM_NOREMOVE);
+  return haveUIMessageWaiting;
+#endif
+}
+
+void
+NotifyActivity(ActivityType aActivityType)
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "HangMonitor::Notify called from off the main thread.");
+
+  // Determine the activity type more specifically
+  if (aActivityType == kGeneralActivity) {
+    aActivityType = IsUIMessageWaiting() ? kActivityUIAVail :
+                                           kActivityNoUIAVail;
+  }
+
+  // Calculate the cumulative amount of lag time since the last UI message
+  static uint32_t cumulativeUILagMS = 0;
+  switch (aActivityType) {
+    case kActivityNoUIAVail:
+      cumulativeUILagMS = 0;
+      break;
+    case kActivityUIAVail:
+    case kUIActivity:
+      if (gTimestamp != PR_INTERVAL_NO_WAIT) {
+        cumulativeUILagMS += PR_IntervalToMilliseconds(PR_IntervalNow() -
+                                                       gTimestamp);
+      }
+      break;
+    default:
+      break;
+  }
+
+  // This is not a locked activity because PRTimeStamp is a 32-bit quantity
+  // which can be read/written atomically, and we don't want to pay locking
+  // penalties here.
+  gTimestamp = PR_IntervalNow();
+
+  // If we have UI activity we should reset the timer and report it
+  if (aActivityType == kUIActivity) {
+    mozilla::Telemetry::Accumulate(mozilla::Telemetry::EVENTLOOP_UI_ACTIVITY_EXP_MS,
+                                     cumulativeUILagMS);
+    cumulativeUILagMS = 0;
+  }
+
+  if (gThread && !gShutdown) {
+    mozilla::BackgroundHangMonitor().NotifyActivity();
+  }
+}
+
+void
+Suspend()
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "HangMonitor::Suspend called from off the main thread.");
+
+  // Because gTimestamp changes this resets the wait count.
+  gTimestamp = PR_INTERVAL_NO_WAIT;
+
+  if (gThread && !gShutdown) {
+    mozilla::BackgroundHangMonitor().NotifyWait();
+  }
+}
+
+} // namespace HangMonitor
+} // namespace mozilla