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gecko/xpcom/threads/HangMonitor.cpp

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/* -*- 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/Monitor.h"
#include "mozilla/Preferences.h"
#include "mozilla/Telemetry.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.
PRInt32 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.
volatile PRIntervalTime gTimestamp = PR_INTERVAL_NO_WAIT;
#ifdef REPORT_CHROME_HANGS
// Main thread ID used in reporting chrome hangs under Windows
static HANDLE winMainThreadHandle = NULL;
// Default timeout for reporting chrome hangs to Telemetry (5 seconds)
static const PRInt32 DEFAULT_CHROME_HANG_INTERVAL = 5;
// Maximum number of PCs to gather from the stack
static const PRInt32 MAX_CALL_STACK_PCS = 400;
#endif
// PrefChangedFunc
int
PrefChanged(const char*, void*)
{
PRInt32 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();
}
return 0;
}
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);
Telemetry::HangStack *callStack =
reinterpret_cast< Telemetry::HangStack* >(aClosure);
if (callStack->Length() < MAX_CALL_STACK_PCS)
callStack->AppendElement(reinterpret_cast<uintptr_t>(aPC));
}
static void
GetChromeHangReport(Telemetry::HangStack &callStack, SharedLibraryInfo &moduleMap)
{
MOZ_ASSERT(winMainThreadHandle);
// The thread we're about to suspend might have the alloc lock
// so allocate ahead of time
callStack.SetCapacity(MAX_CALL_STACK_PCS);
DWORD ret = ::SuspendThread(winMainThreadHandle);
if (ret == -1) {
callStack.Clear();
moduleMap.Clear();
return;
}
NS_StackWalk(ChromeStackWalker, 0, &callStack,
reinterpret_cast<uintptr_t>(winMainThreadHandle));
ret = ::ResumeThread(winMainThreadHandle);
if (ret == -1) {
callStack.Clear();
moduleMap.Clear();
return;
}
moduleMap = SharedLibraryInfo::GetInfoForSelf();
moduleMap.SortByAddress();
// Remove all modules not referenced by a PC on the stack
Telemetry::HangStack sortedStack = callStack;
sortedStack.Sort();
size_t moduleIndex = 0;
size_t stackIndex = 0;
bool unreferencedModule = true;
while (stackIndex < sortedStack.Length() && moduleIndex < moduleMap.GetSize()) {
uintptr_t pc = sortedStack[stackIndex];
SharedLibrary& module = moduleMap.GetEntry(moduleIndex);
uintptr_t moduleStart = module.GetStart();
uintptr_t moduleEnd = module.GetEnd() - 1;
if (moduleStart <= pc && pc <= moduleEnd) {
// If the current PC is within the current module, mark module as used
unreferencedModule = false;
++stackIndex;
} else if (pc > moduleEnd) {
if (unreferencedModule) {
// Remove module if no PCs within its address range
moduleMap.RemoveEntries(moduleIndex, moduleIndex + 1);
} else {
// Module was referenced on stack, but current PC belongs to later module
unreferencedModule = true;
++moduleIndex;
}
} else {
// PC does not belong to any module
++stackIndex;
}
}
// Clean up remaining unreferenced modules, i.e. module addresses > max(pc)
if (moduleIndex + 1 < moduleMap.GetSize()) {
moduleMap.RemoveEntries(moduleIndex + 1, moduleMap.GetSize());
}
}
#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::HangStack hangStack;
SharedLibraryInfo hangModuleMap;
#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;
if (waitCount == 2) {
#ifdef REPORT_CHROME_HANGS
GetChromeHangReport(hangStack, hangModuleMap);
#else
PRInt32 delay =
PRInt32(PR_IntervalToSeconds(now - timestamp));
if (delay > gTimeout) {
MonitorAutoUnlock unlock(*gMonitor);
Crash();
}
#endif
}
}
else {
#ifdef REPORT_CHROME_HANGS
if (waitCount >= 2) {
PRUint32 hangDuration = PR_IntervalToSeconds(now - lastTimestamp);
Telemetry::RecordChromeHang(hangDuration, hangStack, hangModuleMap);
hangStack.Clear();
hangModuleMap.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;
NS_ASSERTION(!gMonitor, "Hang monitor already initialized");
gMonitor = new Monitor("HangMonitor");
Preferences::RegisterCallback(PrefChanged, kHangMonitorPrefName, NULL);
PrefChanged(NULL, NULL);
#ifdef REPORT_CHROME_HANGS
Preferences::RegisterCallback(PrefChanged, kTelemetryPrefName, NULL);
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,
NULL, PR_PRIORITY_LOW, PR_GLOBAL_THREAD,
PR_JOINABLE_THREAD, 0);
}
void
Shutdown()
{
if (GeckoProcessType_Default != XRE_GetProcessType())
return;
NS_ASSERTION(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 = NULL;
}
delete gMonitor;
gMonitor = NULL;
}
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, NULL, WM_KEYFIRST,
WM_IME_KEYLAST, PM_NOREMOVE);
haveUIMessageWaiting |= ::PeekMessageW(&msg, NULL, NS_WM_IMEFIRST,
NS_WM_IMELAST, PM_NOREMOVE);
haveUIMessageWaiting |= ::PeekMessageW(&msg, NULL, WM_MOUSEFIRST,
WM_MOUSELAST, PM_NOREMOVE);
return haveUIMessageWaiting;
#endif
}
void
NotifyActivity(ActivityType activityType)
{
NS_ASSERTION(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 PRUint32 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;
}
// 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 PRUint32 kUIResponsivenessThresholdMS = 50;
if (cumulativeUILagMS > kUIResponsivenessThresholdMS) {
mozilla::Telemetry::Accumulate(mozilla::Telemetry::EVENTLOOP_UI_LAG_EXP_MS,
cumulativeUILagMS);
}
cumulativeUILagMS = 0;
}
}
void
Suspend()
{
NS_ASSERTION(NS_IsMainThread(), "HangMonitor::Suspend called from off the main thread.");
// Because gTimestamp changes this resets the wait count.
gTimestamp = PR_INTERVAL_NO_WAIT;
}
} } // namespace mozilla::HangMonitor
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