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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/SharedThreadPool.h"
#include "mozilla/Monitor.h"
#include "mozilla/ReentrantMonitor.h"
#include "mozilla/Services.h"
#include "mozilla/StaticPtr.h"
#include "nsDataHashtable.h"
#include "nsXPCOMCIDInternal.h"
#include "nsComponentManagerUtils.h"
#include "nsIObserver.h"
#include "nsIObserverService.h"
#ifdef XP_WIN
#include "ThreadPoolCOMListener.h"
#endif
namespace mozilla {
// Created and destroyed on the main thread.
static StaticAutoPtr<ReentrantMonitor> sMonitor;
// Hashtable, maps thread pool name to SharedThreadPool instance.
// Modified only on the main thread.
static StaticAutoPtr<nsDataHashtable<nsCStringHashKey, SharedThreadPool*>> sPools;
static already_AddRefed<nsIThreadPool>
CreateThreadPool(const nsCString& aName);
class SharedThreadPoolShutdownObserver : public nsIObserver
{
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIOBSERVER
protected:
virtual ~SharedThreadPoolShutdownObserver() {}
};
NS_IMPL_ISUPPORTS(SharedThreadPoolShutdownObserver, nsIObserver, nsISupports)
NS_IMETHODIMP
SharedThreadPoolShutdownObserver::Observe(nsISupports* aSubject, const char *aTopic,
const char16_t *aData)
{
MOZ_RELEASE_ASSERT(!strcmp(aTopic, "xpcom-shutdown-threads"));
SharedThreadPool::SpinUntilEmpty();
sMonitor = nullptr;
sPools = nullptr;
return NS_OK;
}
void
SharedThreadPool::InitStatics()
{
MOZ_ASSERT(NS_IsMainThread());
MOZ_ASSERT(!sMonitor && !sPools);
sMonitor = new ReentrantMonitor("SharedThreadPool");
sPools = new nsDataHashtable<nsCStringHashKey, SharedThreadPool*>();
nsCOMPtr<nsIObserverService> obsService = mozilla::services::GetObserverService();
nsCOMPtr<nsIObserver> obs = new SharedThreadPoolShutdownObserver();
obsService->AddObserver(obs, "xpcom-shutdown-threads", false);
}
/* static */
bool
SharedThreadPool::IsEmpty()
{
ReentrantMonitorAutoEnter mon(*sMonitor);
return !sPools->Count();
}
/* static */
void
SharedThreadPool::SpinUntilEmpty()
{
MOZ_ASSERT(NS_IsMainThread());
while (!IsEmpty()) {
sMonitor->AssertNotCurrentThreadIn();
NS_ProcessNextEvent(NS_GetCurrentThread(), true);
}
}
already_AddRefed<SharedThreadPool>
SharedThreadPool::Get(const nsCString& aName, uint32_t aThreadLimit)
{
MOZ_ASSERT(sMonitor && sPools);
ReentrantMonitorAutoEnter mon(*sMonitor);
SharedThreadPool* pool = nullptr;
nsresult rv;
if (!sPools->Get(aName, &pool)) {
nsCOMPtr<nsIThreadPool> threadPool(CreateThreadPool(aName));
NS_ENSURE_TRUE(threadPool, nullptr);
pool = new SharedThreadPool(aName, threadPool);
// Set the thread and idle limits. Note that we don't rely on the
// EnsureThreadLimitIsAtLeast() call below, as the default thread limit
// is 4, and if aThreadLimit is less than 4 we'll end up with a pool
// with 4 threads rather than what we expected; so we'll have unexpected
// behaviour.
rv = pool->SetThreadLimit(aThreadLimit);
NS_ENSURE_SUCCESS(rv, nullptr);
rv = pool->SetIdleThreadLimit(aThreadLimit);
NS_ENSURE_SUCCESS(rv, nullptr);
sPools->Put(aName, pool);
} else if (NS_FAILED(pool->EnsureThreadLimitIsAtLeast(aThreadLimit))) {
NS_WARNING("Failed to set limits on thread pool");
}
MOZ_ASSERT(pool);
RefPtr<SharedThreadPool> instance(pool);
return instance.forget();
}
NS_IMETHODIMP_(MozExternalRefCountType) SharedThreadPool::AddRef(void)
{
MOZ_ASSERT(sMonitor);
ReentrantMonitorAutoEnter mon(*sMonitor);
MOZ_ASSERT(int32_t(mRefCnt) >= 0, "illegal refcnt");
nsrefcnt count = ++mRefCnt;
NS_LOG_ADDREF(this, count, "SharedThreadPool", sizeof(*this));
return count;
}
NS_IMETHODIMP_(MozExternalRefCountType) SharedThreadPool::Release(void)
{
MOZ_ASSERT(sMonitor);
ReentrantMonitorAutoEnter mon(*sMonitor);
nsrefcnt count = --mRefCnt;
NS_LOG_RELEASE(this, count, "SharedThreadPool");
if (count) {
return count;
}
// Remove SharedThreadPool from table of pools.
sPools->Remove(mName);
MOZ_ASSERT(!sPools->Get(mName));
// Dispatch an event to the main thread to call Shutdown() on
// the nsIThreadPool. The Runnable here will add a refcount to the pool,
// and when the Runnable releases the nsIThreadPool it will be deleted.
NS_DispatchToMainThread(NewRunnableMethod(mPool, &nsIThreadPool::Shutdown));
// Stabilize refcount, so that if something in the dtor QIs, it won't explode.
mRefCnt = 1;
delete this;
return 0;
}
NS_IMPL_QUERY_INTERFACE(SharedThreadPool, nsIThreadPool, nsIEventTarget)
SharedThreadPool::SharedThreadPool(const nsCString& aName,
nsIThreadPool* aPool)
: mName(aName)
, mPool(aPool)
, mRefCnt(0)
{
MOZ_COUNT_CTOR(SharedThreadPool);
mEventTarget = do_QueryInterface(aPool);
}
SharedThreadPool::~SharedThreadPool()
{
MOZ_COUNT_DTOR(SharedThreadPool);
}
nsresult
SharedThreadPool::EnsureThreadLimitIsAtLeast(uint32_t aLimit)
{
// We limit the number of threads that we use. Note that we
// set the thread limit to the same as the idle limit so that we're not
// constantly creating and destroying threads (see Bug 881954). When the
// thread pool threads shutdown they dispatch an event to the main thread
// to call nsIThread::Shutdown(), and if we're very busy that can take a
// while to run, and we end up with dozens of extra threads. Note that
// threads that are idle for 60 seconds are shutdown naturally.
uint32_t existingLimit = 0;
nsresult rv;
rv = mPool->GetThreadLimit(&existingLimit);
NS_ENSURE_SUCCESS(rv, rv);
if (aLimit > existingLimit) {
rv = mPool->SetThreadLimit(aLimit);
NS_ENSURE_SUCCESS(rv, rv);
}
rv = mPool->GetIdleThreadLimit(&existingLimit);
NS_ENSURE_SUCCESS(rv, rv);
if (aLimit > existingLimit) {
rv = mPool->SetIdleThreadLimit(aLimit);
NS_ENSURE_SUCCESS(rv, rv);
}
return NS_OK;
}
static already_AddRefed<nsIThreadPool>
CreateThreadPool(const nsCString& aName)
{
nsresult rv;
nsCOMPtr<nsIThreadPool> pool = do_CreateInstance(NS_THREADPOOL_CONTRACTID, &rv);
NS_ENSURE_SUCCESS(rv, nullptr);
rv = pool->SetName(aName);
NS_ENSURE_SUCCESS(rv, nullptr);
rv = pool->SetThreadStackSize(SharedThreadPool::kStackSize);
NS_ENSURE_SUCCESS(rv, nullptr);
#ifdef XP_WIN
// Ensure MSCOM is initialized on the thread pools threads.
nsCOMPtr<nsIThreadPoolListener> listener = new MSCOMInitThreadPoolListener();
rv = pool->SetListener(listener);
NS_ENSURE_SUCCESS(rv, nullptr);
#endif
return pool.forget();
}
} // namespace mozilla
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