gecko/xpcom/threads/nsThreadPool.cpp
2012-05-21 12:12:37 +01:00

335 lines
8.9 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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 "nsIClassInfoImpl.h"
#include "nsThreadPool.h"
#include "nsThreadManager.h"
#include "nsThread.h"
#include "nsMemory.h"
#include "nsAutoPtr.h"
#include "prinrval.h"
#include "prlog.h"
using namespace mozilla;
#ifdef PR_LOGGING
static PRLogModuleInfo *sLog = PR_NewLogModule("nsThreadPool");
#endif
#define LOG(args) PR_LOG(sLog, PR_LOG_DEBUG, args)
// DESIGN:
// o Allocate anonymous threads.
// o Use nsThreadPool::Run as the main routine for each thread.
// o Each thread waits on the event queue's monitor, checking for
// pending events and rescheduling itself as an idle thread.
#define DEFAULT_THREAD_LIMIT 4
#define DEFAULT_IDLE_THREAD_LIMIT 1
#define DEFAULT_IDLE_THREAD_TIMEOUT PR_SecondsToInterval(60)
NS_IMPL_THREADSAFE_ADDREF(nsThreadPool)
NS_IMPL_THREADSAFE_RELEASE(nsThreadPool)
NS_IMPL_CLASSINFO(nsThreadPool, NULL, nsIClassInfo::THREADSAFE,
NS_THREADPOOL_CID)
NS_IMPL_QUERY_INTERFACE3_CI(nsThreadPool, nsIThreadPool, nsIEventTarget,
nsIRunnable)
NS_IMPL_CI_INTERFACE_GETTER2(nsThreadPool, nsIThreadPool, nsIEventTarget)
nsThreadPool::nsThreadPool()
: mThreadLimit(DEFAULT_THREAD_LIMIT)
, mIdleThreadLimit(DEFAULT_IDLE_THREAD_LIMIT)
, mIdleThreadTimeout(DEFAULT_IDLE_THREAD_TIMEOUT)
, mIdleCount(0)
, mShutdown(false)
{
}
nsThreadPool::~nsThreadPool()
{
Shutdown();
}
nsresult
nsThreadPool::PutEvent(nsIRunnable *event)
{
// Avoid spawning a new thread while holding the event queue lock...
bool spawnThread = false;
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
LOG(("THRD-P(%p) put [%d %d %d]\n", this, mIdleCount, mThreads.Count(),
mThreadLimit));
NS_ASSERTION(mIdleCount <= (PRUint32) mThreads.Count(), "oops");
// Make sure we have a thread to service this event.
if (mIdleCount == 0 && mThreads.Count() < (PRInt32) mThreadLimit)
spawnThread = true;
mEvents.PutEvent(event);
}
LOG(("THRD-P(%p) put [spawn=%d]\n", this, spawnThread));
if (!spawnThread)
return NS_OK;
nsCOMPtr<nsIThread> thread;
nsThreadManager::get()->NewThread(0,
nsIThreadManager::DEFAULT_STACK_SIZE,
getter_AddRefs(thread));
NS_ENSURE_STATE(thread);
bool killThread = false;
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
if (mThreads.Count() < (PRInt32) mThreadLimit) {
mThreads.AppendObject(thread);
} else {
killThread = true; // okay, we don't need this thread anymore
}
}
LOG(("THRD-P(%p) put [%p kill=%d]\n", this, thread.get(), killThread));
if (killThread) {
thread->Shutdown();
} else {
thread->Dispatch(this, NS_DISPATCH_NORMAL);
}
return NS_OK;
}
void
nsThreadPool::ShutdownThread(nsIThread *thread)
{
LOG(("THRD-P(%p) shutdown async [%p]\n", this, thread));
// This method is responsible for calling Shutdown on |thread|. This must be
// done from some other thread, so we use the main thread of the application.
NS_ASSERTION(!NS_IsMainThread(), "wrong thread");
nsRefPtr<nsIRunnable> r = NS_NewRunnableMethod(thread, &nsIThread::Shutdown);
NS_DispatchToMainThread(r);
}
NS_IMETHODIMP
nsThreadPool::Run()
{
LOG(("THRD-P(%p) enter\n", this));
nsCOMPtr<nsIThread> current;
nsThreadManager::get()->GetCurrentThread(getter_AddRefs(current));
bool shutdownThreadOnExit = false;
bool exitThread = false;
bool wasIdle = false;
PRIntervalTime idleSince;
nsCOMPtr<nsIThreadPoolListener> listener;
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
listener = mListener;
}
if (listener) {
listener->OnThreadCreated();
}
do {
nsCOMPtr<nsIRunnable> event;
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
if (!mEvents.GetPendingEvent(getter_AddRefs(event))) {
PRIntervalTime now = PR_IntervalNow();
PRIntervalTime timeout = PR_MillisecondsToInterval(mIdleThreadTimeout);
// If we are shutting down, then don't keep any idle threads
if (mShutdown) {
exitThread = true;
} else {
if (wasIdle) {
// if too many idle threads or idle for too long, then bail.
if (mIdleCount > mIdleThreadLimit || (now - idleSince) >= timeout)
exitThread = true;
} else {
// if would be too many idle threads...
if (mIdleCount == mIdleThreadLimit) {
exitThread = true;
} else {
++mIdleCount;
idleSince = now;
wasIdle = true;
}
}
}
if (exitThread) {
if (wasIdle)
--mIdleCount;
shutdownThreadOnExit = mThreads.RemoveObject(current);
} else {
PRIntervalTime delta = timeout - (now - idleSince);
LOG(("THRD-P(%p) waiting [%d]\n", this, delta));
mon.Wait(delta);
}
} else if (wasIdle) {
wasIdle = false;
--mIdleCount;
}
}
if (event) {
LOG(("THRD-P(%p) running [%p]\n", this, event.get()));
event->Run();
}
} while (!exitThread);
if (listener) {
listener->OnThreadShuttingDown();
}
if (shutdownThreadOnExit) {
ShutdownThread(current);
}
LOG(("THRD-P(%p) leave\n", this));
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::Dispatch(nsIRunnable *event, PRUint32 flags)
{
LOG(("THRD-P(%p) dispatch [%p %x]\n", this, event, flags));
NS_ENSURE_STATE(!mShutdown);
if (flags & DISPATCH_SYNC) {
nsCOMPtr<nsIThread> thread;
nsThreadManager::get()->GetCurrentThread(getter_AddRefs(thread));
NS_ENSURE_STATE(thread);
nsRefPtr<nsThreadSyncDispatch> wrapper =
new nsThreadSyncDispatch(thread, event);
PutEvent(wrapper);
while (wrapper->IsPending())
NS_ProcessNextEvent(thread);
} else {
NS_ASSERTION(flags == NS_DISPATCH_NORMAL, "unexpected dispatch flags");
PutEvent(event);
}
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::IsOnCurrentThread(bool *result)
{
// No one should be calling this method. If this assertion gets hit, then we
// need to think carefully about what this method should be returning.
NS_NOTREACHED("implement me");
*result = false;
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::Shutdown()
{
nsCOMArray<nsIThread> threads;
nsCOMPtr<nsIThreadPoolListener> listener;
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
mShutdown = true;
mon.NotifyAll();
threads.AppendObjects(mThreads);
mThreads.Clear();
// Swap in a null listener so that we release the listener at the end of
// this method. The listener will be kept alive as long as the other threads
// that were created when it was set.
mListener.swap(listener);
}
// It's important that we shutdown the threads while outside the event queue
// monitor. Otherwise, we could end up dead-locking.
for (PRInt32 i = 0; i < threads.Count(); ++i)
threads[i]->Shutdown();
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::GetThreadLimit(PRUint32 *value)
{
*value = mThreadLimit;
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::SetThreadLimit(PRUint32 value)
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
mThreadLimit = value;
if (mIdleThreadLimit > mThreadLimit)
mIdleThreadLimit = mThreadLimit;
mon.NotifyAll(); // wake up threads so they observe this change
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::GetIdleThreadLimit(PRUint32 *value)
{
*value = mIdleThreadLimit;
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::SetIdleThreadLimit(PRUint32 value)
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
mIdleThreadLimit = value;
if (mIdleThreadLimit > mThreadLimit)
mIdleThreadLimit = mThreadLimit;
mon.NotifyAll(); // wake up threads so they observe this change
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::GetIdleThreadTimeout(PRUint32 *value)
{
*value = mIdleThreadTimeout;
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::SetIdleThreadTimeout(PRUint32 value)
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
mIdleThreadTimeout = value;
mon.NotifyAll(); // wake up threads so they observe this change
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::GetListener(nsIThreadPoolListener** aListener)
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
NS_IF_ADDREF(*aListener = mListener);
return NS_OK;
}
NS_IMETHODIMP
nsThreadPool::SetListener(nsIThreadPoolListener* aListener)
{
nsCOMPtr<nsIThreadPoolListener> swappedListener(aListener);
{
ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
mListener.swap(swappedListener);
}
return NS_OK;
}