gecko-dev/xpcom/threads/nsThreadManager.cpp

343 строки
9.3 KiB
C++

/* -*- 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 "nsThreadManager.h"
#include "nsThread.h"
#include "nsThreadUtils.h"
#include "nsIClassInfoImpl.h"
#include "nsTArray.h"
#include "nsAutoPtr.h"
#include "mozilla/ThreadLocal.h"
#ifdef MOZ_CANARY
#include <fcntl.h>
#include <unistd.h>
#endif
#include "MainThreadIdlePeriod.h"
using namespace mozilla;
static MOZ_THREAD_LOCAL(bool) sTLSIsMainThread;
bool
NS_IsMainThread()
{
return sTLSIsMainThread.get();
}
void
NS_SetMainThread()
{
if (!sTLSIsMainThread.init()) {
MOZ_CRASH();
}
sTLSIsMainThread.set(true);
MOZ_ASSERT(NS_IsMainThread());
}
typedef nsTArray<NotNull<RefPtr<nsThread>>> nsThreadArray;
//-----------------------------------------------------------------------------
static void
ReleaseObject(void* aData)
{
static_cast<nsISupports*>(aData)->Release();
}
// statically allocated instance
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadManager::AddRef()
{
return 2;
}
NS_IMETHODIMP_(MozExternalRefCountType)
nsThreadManager::Release()
{
return 1;
}
NS_IMPL_CLASSINFO(nsThreadManager, nullptr,
nsIClassInfo::THREADSAFE | nsIClassInfo::SINGLETON,
NS_THREADMANAGER_CID)
NS_IMPL_QUERY_INTERFACE_CI(nsThreadManager, nsIThreadManager)
NS_IMPL_CI_INTERFACE_GETTER(nsThreadManager, nsIThreadManager)
//-----------------------------------------------------------------------------
nsresult
nsThreadManager::Init()
{
// Child processes need to initialize the thread manager before they
// initialize XPCOM in order to set up the crash reporter. This leads to
// situations where we get initialized twice.
if (mInitialized) {
return NS_OK;
}
if (PR_NewThreadPrivateIndex(&mCurThreadIndex, ReleaseObject) == PR_FAILURE) {
return NS_ERROR_FAILURE;
}
#ifdef MOZ_CANARY
const int flags = O_WRONLY | O_APPEND | O_CREAT | O_NONBLOCK;
const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
char* env_var_flag = getenv("MOZ_KILL_CANARIES");
sCanaryOutputFD =
env_var_flag ? (env_var_flag[0] ? open(env_var_flag, flags, mode) :
STDERR_FILENO) :
0;
#endif
// Setup "main" thread
mMainThread = new nsThread(nsThread::MAIN_THREAD, 0);
nsresult rv = mMainThread->InitCurrentThread();
if (NS_FAILED(rv)) {
mMainThread = nullptr;
return rv;
}
{
nsCOMPtr<nsIIdlePeriod> idlePeriod = new MainThreadIdlePeriod();
mMainThread->RegisterIdlePeriod(idlePeriod.forget());
}
// We need to keep a pointer to the current thread, so we can satisfy
// GetIsMainThread calls that occur post-Shutdown.
mMainThread->GetPRThread(&mMainPRThread);
mInitialized = true;
return NS_OK;
}
void
nsThreadManager::Shutdown()
{
MOZ_ASSERT(NS_IsMainThread(), "shutdown not called from main thread");
// Prevent further access to the thread manager (no more new threads!)
//
// What happens if shutdown happens before NewThread completes?
// We Shutdown() the new thread, and return error if we've started Shutdown
// between when NewThread started, and when the thread finished initializing
// and registering with ThreadManager.
//
mInitialized = false;
// Empty the main thread event queue before we begin shutting down threads.
NS_ProcessPendingEvents(mMainThread);
// We gather the threads from the hashtable into a list, so that we avoid
// holding the hashtable lock while calling nsIThread::Shutdown.
nsThreadArray threads;
{
OffTheBooksMutexAutoLock lock(mLock);
for (auto iter = mThreadsByPRThread.Iter(); !iter.Done(); iter.Next()) {
RefPtr<nsThread>& thread = iter.Data();
threads.AppendElement(WrapNotNull(thread));
iter.Remove();
}
}
// It's tempting to walk the list of threads here and tell them each to stop
// accepting new events, but that could lead to badness if one of those
// threads is stuck waiting for a response from another thread. To do it
// right, we'd need some way to interrupt the threads.
//
// Instead, we process events on the current thread while waiting for threads
// to shutdown. This means that we have to preserve a mostly functioning
// world until such time as the threads exit.
// Shutdown all threads that require it (join with threads that we created).
for (uint32_t i = 0; i < threads.Length(); ++i) {
NotNull<nsThread*> thread = threads[i];
if (thread->ShutdownRequired()) {
thread->Shutdown();
}
}
// NB: It's possible that there are events in the queue that want to *start*
// an asynchronous shutdown. But we have already shutdown the threads above,
// so there's no need to worry about them. We only have to wait for all
// in-flight asynchronous thread shutdowns to complete.
mMainThread->WaitForAllAsynchronousShutdowns();
// In case there are any more events somehow...
NS_ProcessPendingEvents(mMainThread);
// There are no more background threads at this point.
// Clear the table of threads.
{
OffTheBooksMutexAutoLock lock(mLock);
mThreadsByPRThread.Clear();
}
// Normally thread shutdown clears the observer for the thread, but since the
// main thread is special we do it manually here after we're sure all events
// have been processed.
mMainThread->SetObserver(nullptr);
mMainThread->ClearObservers();
// Release main thread object.
mMainThread = nullptr;
// Remove the TLS entry for the main thread.
PR_SetThreadPrivate(mCurThreadIndex, nullptr);
}
void
nsThreadManager::RegisterCurrentThread(nsThread& aThread)
{
MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");
OffTheBooksMutexAutoLock lock(mLock);
++mCurrentNumberOfThreads;
if (mCurrentNumberOfThreads > mHighestNumberOfThreads) {
mHighestNumberOfThreads = mCurrentNumberOfThreads;
}
mThreadsByPRThread.Put(aThread.GetPRThread(), &aThread); // XXX check OOM?
aThread.AddRef(); // for TLS entry
PR_SetThreadPrivate(mCurThreadIndex, &aThread);
}
void
nsThreadManager::UnregisterCurrentThread(nsThread& aThread)
{
MOZ_ASSERT(aThread.GetPRThread() == PR_GetCurrentThread(), "bad aThread");
OffTheBooksMutexAutoLock lock(mLock);
--mCurrentNumberOfThreads;
mThreadsByPRThread.Remove(aThread.GetPRThread());
PR_SetThreadPrivate(mCurThreadIndex, nullptr);
// Ref-count balanced via ReleaseObject
}
nsThread*
nsThreadManager::GetCurrentThread()
{
// read thread local storage
void* data = PR_GetThreadPrivate(mCurThreadIndex);
if (data) {
return static_cast<nsThread*>(data);
}
if (!mInitialized) {
return nullptr;
}
// OK, that's fine. We'll dynamically create one :-)
RefPtr<nsThread> thread = new nsThread(nsThread::NOT_MAIN_THREAD, 0);
if (!thread || NS_FAILED(thread->InitCurrentThread())) {
return nullptr;
}
return thread.get(); // reference held in TLS
}
NS_IMETHODIMP
nsThreadManager::NewThread(uint32_t aCreationFlags,
uint32_t aStackSize,
nsIThread** aResult)
{
// Note: can be called from arbitrary threads
// No new threads during Shutdown
if (NS_WARN_IF(!mInitialized)) {
return NS_ERROR_NOT_INITIALIZED;
}
RefPtr<nsThread> thr = new nsThread(nsThread::NOT_MAIN_THREAD, aStackSize);
nsresult rv = thr->Init(); // Note: blocks until the new thread has been set up
if (NS_FAILED(rv)) {
return rv;
}
// At this point, we expect that the thread has been registered in mThreadByPRThread;
// however, it is possible that it could have also been replaced by now, so
// we cannot really assert that it was added. Instead, kill it if we entered
// Shutdown() during/before Init()
if (NS_WARN_IF(!mInitialized)) {
if (thr->ShutdownRequired()) {
thr->Shutdown(); // ok if it happens multiple times
}
return NS_ERROR_NOT_INITIALIZED;
}
thr.forget(aResult);
return NS_OK;
}
NS_IMETHODIMP
nsThreadManager::GetThreadFromPRThread(PRThread* aThread, nsIThread** aResult)
{
// Keep this functioning during Shutdown
if (NS_WARN_IF(!mMainThread)) {
return NS_ERROR_NOT_INITIALIZED;
}
if (NS_WARN_IF(!aThread)) {
return NS_ERROR_INVALID_ARG;
}
RefPtr<nsThread> temp;
{
OffTheBooksMutexAutoLock lock(mLock);
mThreadsByPRThread.Get(aThread, getter_AddRefs(temp));
}
NS_IF_ADDREF(*aResult = temp);
return NS_OK;
}
NS_IMETHODIMP
nsThreadManager::GetMainThread(nsIThread** aResult)
{
// Keep this functioning during Shutdown
if (NS_WARN_IF(!mMainThread)) {
return NS_ERROR_NOT_INITIALIZED;
}
NS_ADDREF(*aResult = mMainThread);
return NS_OK;
}
NS_IMETHODIMP
nsThreadManager::GetCurrentThread(nsIThread** aResult)
{
// Keep this functioning during Shutdown
if (NS_WARN_IF(!mMainThread)) {
return NS_ERROR_NOT_INITIALIZED;
}
*aResult = GetCurrentThread();
if (!*aResult) {
return NS_ERROR_OUT_OF_MEMORY;
}
NS_ADDREF(*aResult);
return NS_OK;
}
NS_IMETHODIMP
nsThreadManager::GetIsMainThread(bool* aResult)
{
// This method may be called post-Shutdown
*aResult = (PR_GetCurrentThread() == mMainPRThread);
return NS_OK;
}
uint32_t
nsThreadManager::GetHighestNumberOfThreads()
{
OffTheBooksMutexAutoLock lock(mLock);
return mHighestNumberOfThreads;
}