The Tor Browser: xpcom/threads/HangMonitor.cpp@b8a032363ba2 (annotated)

xpcom/threads/HangMonitor.cpp@b8a032363ba2 (annotated)

xpcom/threads/HangMonitor.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- 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 "mozilla/HangMonitor.h"
 #include "mozilla/BackgroundHangMonitor.h"
 #include "mozilla/Monitor.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/ProcessedStack.h"
 #include "mozilla/Atomics.h"
 #include "nsXULAppAPI.h"
 #include "nsThreadUtils.h"
 #include "nsStackWalk.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";
 const char kTelemetryPrefName[] = "toolkit.telemetry.enabled";
 // 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
   CrashReporter::AnnotateCrashReport(NS_LITERAL_CSTRING("Hang"),
                                      NS_LITERAL_CSTRING("1"));
 #endif
   NS_RUNTIMEABORT("HangMonitor triggered");
 }
 #ifdef REPORT_CHROME_HANGS
 static void
 ChromeStackWalker(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);
   DWORD ret = ::SuspendThread(winMainThreadHandle);
   if (ret == -1)
     return;
   NS_StackWalk(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;
 #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);
       }
 #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);
         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()
 {
   // The hang detector only runs in chrome processes. If you change this,
   // you must also deal with the threadsafety of AnnotateCrashReport in
   // non-chrome processes!
   if (GeckoProcessType_Default != 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())
     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 activityType)
 {
   MOZ_ASSERT(NS_IsMainThread(),
              "HangMonitor::Notify called from off the main thread.");
   // Determine the activity type more specifically
   if (activityType == kGeneralActivity) {
     activityType = IsUIMessageWaiting() ? kActivityUIAVail :
                                           kActivityNoUIAVail;
   }
   // Calculate the cumulative amount of lag time since the last UI message
   static uint32_t cumulativeUILagMS = 0;
   switch(activityType) {
   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 it is
   // significant enough.
   if (activityType == kUIActivity) {
     // The minimum amount of lag time that we should report for telemetry data.
     // Mozilla's UI responsiveness goal is 50ms
     static const uint32_t kUIResponsivenessThresholdMS = 50;
     if (cumulativeUILagMS > kUIResponsivenessThresholdMS) {
       mozilla::Telemetry::Accumulate(mozilla::Telemetry::EVENTLOOP_UI_LAG_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 mozilla::HangMonitor

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xpcom/threads/HangMonitor.cpp@b8a032363ba2 (annotated)

xpcom/threads/HangMonitor.cpp