gecko/xpcom/threads/BackgroundHangMonitor.cpp
Birunthan Mohanathas c948872318 Bug 995730 - Convert xpcom/threads/ to Gecko style. r=froydnj
--HG--
extra : rebase_source : 1f6f179f44db87f55ebfe5d855192adfad7d1b74
2014-05-27 10:15:35 +03:00

520 lines
16 KiB
C++

/* -*- 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/ArrayUtils.h"
#include "mozilla/BackgroundHangMonitor.h"
#include "mozilla/LinkedList.h"
#include "mozilla/Monitor.h"
#include "mozilla/Move.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/Telemetry.h"
#include "mozilla/ThreadHangStats.h"
#include "mozilla/ThreadLocal.h"
#ifdef MOZ_NUWA_PROCESS
#include "ipc/Nuwa.h"
#endif
#include "prinrval.h"
#include "prthread.h"
#include "ThreadStackHelper.h"
#include <algorithm>
namespace mozilla {
/**
* BackgroundHangManager is the global object that
* manages all instances of BackgroundHangThread.
*/
class BackgroundHangManager
{
private:
// Background hang monitor thread function
static void MonitorThread(void* aData)
{
PR_SetCurrentThreadName("BgHangManager");
#ifdef MOZ_NUWA_PROCESS
if (IsNuwaProcess()) {
NS_ASSERTION(NuwaMarkCurrentThread,
"NuwaMarkCurrentThread is undefined!");
NuwaMarkCurrentThread(nullptr, nullptr);
}
#endif
/* We do not hold a reference to BackgroundHangManager here
because the monitor thread only exists as long as the
BackgroundHangManager instance exists. We stop the monitor
thread in the BackgroundHangManager destructor, and we can
only get to the destructor if we don't hold a reference here. */
static_cast<BackgroundHangManager*>(aData)->RunMonitorThread();
}
// Hang monitor thread
PRThread* mHangMonitorThread;
// Stop hang monitoring
bool mShutdown;
BackgroundHangManager(const BackgroundHangManager&);
BackgroundHangManager& operator=(const BackgroundHangManager&);
void RunMonitorThread();
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(BackgroundHangManager)
static StaticRefPtr<BackgroundHangManager> sInstance;
// Lock for access to members of this class
Monitor mLock;
// Current time as seen by hang monitors
PRIntervalTime mIntervalNow;
// List of BackgroundHangThread instances associated with each thread
LinkedList<BackgroundHangThread> mHangThreads;
void Shutdown()
{
MonitorAutoLock autoLock(mLock);
mShutdown = true;
autoLock.Notify();
}
void Wakeup()
{
// PR_CreateThread could have failed earlier
if (mHangMonitorThread) {
// Use PR_Interrupt to avoid potentially taking a lock
PR_Interrupt(mHangMonitorThread);
}
}
BackgroundHangManager();
~BackgroundHangManager();
};
/**
* BackgroundHangThread is a per-thread object that is used
* by all instances of BackgroundHangMonitor to monitor hangs.
*/
class BackgroundHangThread : public LinkedListElement<BackgroundHangThread>
{
private:
static ThreadLocal<BackgroundHangThread*> sTlsKey;
BackgroundHangThread(const BackgroundHangThread&);
BackgroundHangThread& operator=(const BackgroundHangThread&);
~BackgroundHangThread();
/* Keep a reference to the manager, so we can keep going even
after BackgroundHangManager::Shutdown is called. */
const RefPtr<BackgroundHangManager> mManager;
// Unique thread ID for identification
const PRThread* mThreadID;
public:
NS_INLINE_DECL_REFCOUNTING(BackgroundHangThread)
static BackgroundHangThread* FindThread();
static void Startup()
{
/* We can tolerate init() failing. */
(void)!sTlsKey.init();
}
// Hang timeout in ticks
const PRIntervalTime mTimeout;
// PermaHang timeout in ticks
const PRIntervalTime mMaxTimeout;
// Time at last activity
PRIntervalTime mInterval;
// Time when a hang started
PRIntervalTime mHangStart;
// Is the thread in a hang
bool mHanging;
// Is the thread in a waiting state
bool mWaiting;
// Platform-specific helper to get hang stacks
ThreadStackHelper mStackHelper;
// Stack of current hang
Telemetry::HangHistogram::Stack mHangStack;
// Statistics for telemetry
Telemetry::ThreadHangStats mStats;
BackgroundHangThread(const char* aName,
uint32_t aTimeoutMs,
uint32_t aMaxTimeoutMs);
// Report a hang; aManager->mLock IS locked
void ReportHang(PRIntervalTime aHangTime);
// Report a permanent hang; aManager->mLock IS locked
void ReportPermaHang();
// Called by BackgroundHangMonitor::NotifyActivity
void NotifyActivity();
// Called by BackgroundHangMonitor::NotifyWait
void NotifyWait()
{
NotifyActivity();
mWaiting = true;
}
};
StaticRefPtr<BackgroundHangManager> BackgroundHangManager::sInstance;
ThreadLocal<BackgroundHangThread*> BackgroundHangThread::sTlsKey;
BackgroundHangManager::BackgroundHangManager()
: mShutdown(false)
, mLock("BackgroundHangManager")
, mIntervalNow(0)
{
// Lock so we don't race against the new monitor thread
MonitorAutoLock autoLock(mLock);
mHangMonitorThread = PR_CreateThread(
PR_USER_THREAD, MonitorThread, this,
PR_PRIORITY_LOW, PR_GLOBAL_THREAD, PR_JOINABLE_THREAD, 0);
MOZ_ASSERT(mHangMonitorThread, "Failed to create monitor thread");
}
BackgroundHangManager::~BackgroundHangManager()
{
MOZ_ASSERT(mShutdown, "Destruction without Shutdown call");
MOZ_ASSERT(mHangThreads.isEmpty(), "Destruction with outstanding monitors");
MOZ_ASSERT(mHangMonitorThread, "No monitor thread");
// PR_CreateThread could have failed above due to resource limitation
if (mHangMonitorThread) {
// The monitor thread can only live as long as the instance lives
PR_JoinThread(mHangMonitorThread);
}
}
void
BackgroundHangManager::RunMonitorThread()
{
// Keep us locked except when waiting
MonitorAutoLock autoLock(mLock);
/* mIntervalNow is updated at various intervals determined by waitTime.
However, if an update latency is too long (due to CPU scheduling, system
sleep, etc.), we don't update mIntervalNow at all. This is done so that
long latencies in our timing are not detected as hangs. systemTime is
used to track PR_IntervalNow() and determine our latency. */
PRIntervalTime systemTime = PR_IntervalNow();
// Default values for the first iteration of thread loop
PRIntervalTime waitTime = PR_INTERVAL_NO_WAIT;
PRIntervalTime recheckTimeout = PR_INTERVAL_NO_WAIT;
while (!mShutdown) {
PR_ClearInterrupt();
nsresult rv = autoLock.Wait(waitTime);
PRIntervalTime newTime = PR_IntervalNow();
PRIntervalTime systemInterval = newTime - systemTime;
systemTime = newTime;
/* waitTime is a quarter of the shortest timeout value; If our timing
latency is low enough (less than half the shortest timeout value),
we can update mIntervalNow. */
if (MOZ_LIKELY(waitTime != PR_INTERVAL_NO_TIMEOUT &&
systemInterval < 2 * waitTime)) {
mIntervalNow += systemInterval;
}
/* If it's before the next recheck timeout, and our wait did not
get interrupted (either through Notify or PR_Interrupt), we can
keep the current waitTime and skip iterating through hang monitors. */
if (MOZ_LIKELY(systemInterval < recheckTimeout &&
systemInterval >= waitTime &&
rv == NS_OK)) {
recheckTimeout -= systemInterval;
continue;
}
/* We are in one of the following scenarios,
- Hang or permahang recheck timeout
- Thread added/removed
- Thread wait or hang ended
In all cases, we want to go through our list of hang
monitors and update waitTime and recheckTimeout. */
waitTime = PR_INTERVAL_NO_TIMEOUT;
recheckTimeout = PR_INTERVAL_NO_TIMEOUT;
// Locally hold mIntervalNow
PRIntervalTime intervalNow = mIntervalNow;
// iterate through hang monitors
for (BackgroundHangThread* currentThread = mHangThreads.getFirst();
currentThread; currentThread = currentThread->getNext()) {
if (currentThread->mWaiting) {
// Thread is waiting, not hanging
continue;
}
PRIntervalTime interval = currentThread->mInterval;
PRIntervalTime hangTime = intervalNow - interval;
if (MOZ_UNLIKELY(hangTime >= currentThread->mMaxTimeout)) {
// A permahang started
// 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;
}
} else {
if (MOZ_LIKELY(interval != currentThread->mHangStart)) {
// A hang ended
currentThread->ReportHang(intervalNow - currentThread->mHangStart);
currentThread->mHanging = false;
}
}
/* If we are hanging, the next time we check for hang status is when
the hang turns into a permahang. If we're not hanging, the next
recheck timeout is when we may be entering a hang. */
PRIntervalTime nextRecheck;
if (currentThread->mHanging) {
nextRecheck = currentThread->mMaxTimeout;
} else {
nextRecheck = currentThread->mTimeout;
}
recheckTimeout = std::min(recheckTimeout, nextRecheck - hangTime);
/* We wait for a quarter of the shortest timeout
value to give mIntervalNow enough granularity. */
waitTime = std::min(waitTime, currentThread->mTimeout / 4);
}
}
/* We are shutting down now.
Wait for all outstanding monitors to unregister. */
while (!mHangThreads.isEmpty()) {
autoLock.Wait(PR_INTERVAL_NO_TIMEOUT);
}
}
BackgroundHangThread::BackgroundHangThread(const char* aName,
uint32_t aTimeoutMs,
uint32_t aMaxTimeoutMs)
: mManager(BackgroundHangManager::sInstance)
, mThreadID(PR_GetCurrentThread())
, mTimeout(aTimeoutMs == BackgroundHangMonitor::kNoTimeout
? PR_INTERVAL_NO_TIMEOUT
: PR_MillisecondsToInterval(aTimeoutMs))
, mMaxTimeout(aMaxTimeoutMs == BackgroundHangMonitor::kNoTimeout
? PR_INTERVAL_NO_TIMEOUT
: PR_MillisecondsToInterval(aMaxTimeoutMs))
, mInterval(mManager->mIntervalNow)
, mHangStart(mInterval)
, mHanging(false)
, mWaiting(true)
, mStats(aName)
{
if (sTlsKey.initialized()) {
sTlsKey.set(this);
}
// Lock here because LinkedList is not thread-safe
MonitorAutoLock autoLock(mManager->mLock);
// Add to thread list
mManager->mHangThreads.insertBack(this);
// Wake up monitor thread to process new thread
autoLock.Notify();
}
BackgroundHangThread::~BackgroundHangThread()
{
// Lock here because LinkedList is not thread-safe
MonitorAutoLock autoLock(mManager->mLock);
// Remove from thread list
remove();
// Wake up monitor thread to process removed thread
autoLock.Notify();
// We no longer have a thread
if (sTlsKey.initialized()) {
sTlsKey.set(nullptr);
}
// Move our copy of ThreadHangStats to Telemetry storage
Telemetry::RecordThreadHangStats(mStats);
}
void
BackgroundHangThread::ReportHang(PRIntervalTime aHangTime)
{
// Recovered from a hang; called on the monitor thread
// mManager->mLock IS locked
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);
return;
}
}
// Add new histogram
newHistogram.Add(aHangTime);
mStats.mHangs.append(Move(newHistogram));
}
void
BackgroundHangThread::ReportPermaHang()
{
// Permanently hanged; called on the monitor thread
// mManager->mLock IS locked
// TODO: Add more detailed analysis for perma-hangs
ReportHang(mMaxTimeout);
}
MOZ_ALWAYS_INLINE void
BackgroundHangThread::NotifyActivity()
{
PRIntervalTime intervalNow = mManager->mIntervalNow;
if (mWaiting) {
mInterval = intervalNow;
mWaiting = false;
/* We have to wake up the manager thread because when all threads
are waiting, the manager thread waits indefinitely as well. */
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();
}
mInterval = intervalNow;
}
}
BackgroundHangThread*
BackgroundHangThread::FindThread()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
if (sTlsKey.initialized()) {
// Use TLS if available
return sTlsKey.get();
}
// If TLS is unavailable, we can search through the thread list
RefPtr<BackgroundHangManager> manager(BackgroundHangManager::sInstance);
MOZ_ASSERT(manager, "Creating BackgroundHangMonitor after shutdown");
PRThread* threadID = PR_GetCurrentThread();
// Lock thread list for traversal
MonitorAutoLock autoLock(manager->mLock);
for (BackgroundHangThread* thread = manager->mHangThreads.getFirst();
thread; thread = thread->getNext()) {
if (thread->mThreadID == threadID) {
return thread;
}
}
#endif
// Current thread is not initialized
return nullptr;
}
void
BackgroundHangMonitor::Startup()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
MOZ_ASSERT(!BackgroundHangManager::sInstance, "Already initialized");
ThreadStackHelper::Startup();
BackgroundHangThread::Startup();
BackgroundHangManager::sInstance = new BackgroundHangManager();
#endif
}
void
BackgroundHangMonitor::Shutdown()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
MOZ_ASSERT(BackgroundHangManager::sInstance, "Not initialized");
/* Scope our lock inside Shutdown() because the sInstance object can
be destroyed as soon as we set sInstance to nullptr below, and
we don't want to hold the lock when it's being destroyed. */
BackgroundHangManager::sInstance->Shutdown();
BackgroundHangManager::sInstance = nullptr;
ThreadStackHelper::Shutdown();
#endif
}
BackgroundHangMonitor::BackgroundHangMonitor(const char* aName,
uint32_t aTimeoutMs,
uint32_t aMaxTimeoutMs)
: mThread(BackgroundHangThread::FindThread())
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
if (!mThread) {
mThread = new BackgroundHangThread(aName, aTimeoutMs, aMaxTimeoutMs);
}
#endif
}
BackgroundHangMonitor::BackgroundHangMonitor()
: mThread(BackgroundHangThread::FindThread())
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
MOZ_ASSERT(mThread, "Thread not initialized for hang monitoring");
#endif
}
BackgroundHangMonitor::~BackgroundHangMonitor()
{
}
void
BackgroundHangMonitor::NotifyActivity()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
mThread->NotifyActivity();
#endif
}
void
BackgroundHangMonitor::NotifyWait()
{
#ifdef MOZ_ENABLE_BACKGROUND_HANG_MONITOR
mThread->NotifyWait();
#endif
}
/* Because we are iterating through the BackgroundHangThread linked list,
we need to take a lock. Using MonitorAutoLock as a base class makes
sure all of that is taken care of for us. */
BackgroundHangMonitor::ThreadHangStatsIterator::ThreadHangStatsIterator()
: MonitorAutoLock(BackgroundHangManager::sInstance->mLock)
, mThread(BackgroundHangManager::sInstance->mHangThreads.getFirst())
{
}
Telemetry::ThreadHangStats*
BackgroundHangMonitor::ThreadHangStatsIterator::GetNext()
{
if (!mThread) {
return nullptr;
}
Telemetry::ThreadHangStats* stats = &mThread->mStats;
mThread = mThread->getNext();
return stats;
}
} // namespace mozilla