The Tor Browser: content/media/SharedThreadPool.cpp@44a2da4a2ab2 (annotated)

content/media/SharedThreadPool.cpp@44a2da4a2ab2 (annotated)

content/media/SharedThreadPool.cpp

Fri, 16 Jan 2015 04:50:19 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 04:50:19 +0100
branch: TOR_BUG_9701
changeset 13: 44a2da4a2ab2
permissions: -rw-r--r--

Replace accessor implementation with direct member state manipulation, by
request https://trac.torproject.org/projects/tor/ticket/9701#comment:32

 /* -*- 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 "SharedThreadPool.h"
 #include "mozilla/Monitor.h"
 #include "mozilla/StaticPtr.h"
 #include "nsDataHashtable.h"
 #include "VideoUtils.h"
 #include "nsXPCOMCIDInternal.h"
 #include "nsComponentManagerUtils.h"
 #ifdef XP_WIN
 // Required to init MSCOM by MSCOMInitThreadPoolListener.
 #include <objbase.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);
 static void
 DestroySharedThreadPoolHashTable();
 void
 SharedThreadPool::EnsureInitialized()
 {
   MOZ_ASSERT(NS_IsMainThread());
   if (sMonitor || sPools) {
     // Already initalized.
     return;
   }
   sMonitor = new ReentrantMonitor("SharedThreadPool");
   sPools = new nsDataHashtable<nsCStringHashKey, SharedThreadPool*>();
 }
 class ShutdownPoolsEvent : public nsRunnable {
 public:
   NS_IMETHODIMP Run() {
     MOZ_ASSERT(NS_IsMainThread());
     DestroySharedThreadPoolHashTable();
     return NS_OK;
   }
 };
 static void
 DestroySharedThreadPoolHashTable()
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(sMonitor && sPools);
   if (!sPools->Count()) {
     // No more SharedThreadPool singletons. Delete the hash table.
     // Note we don't need to lock sMonitor, since we only modify the
     // hash table on the main thread, and if the hash table is empty
     // there are no external references into its contents.
     sPools = nullptr;
     sMonitor = nullptr;
   }
 }
 /* static */
 void
 SharedThreadPool::SpinUntilShutdown()
 {
   MOZ_ASSERT(NS_IsMainThread());
   // Wait until the ShutdownPoolsEvent has been run and shutdown the pool.
   while (sPools) {
     if (!NS_ProcessNextEvent(NS_GetCurrentThread(), true)) {
       break;
     }
   }
   MOZ_ASSERT(!sPools);
   MOZ_ASSERT(!sMonitor);
 }
 TemporaryRef<SharedThreadPool>
 SharedThreadPool::Get(const nsCString& aName, uint32_t aThreadLimit)
 {
   MOZ_ASSERT(NS_IsMainThread());
   EnsureInitialized();
   MOZ_ASSERT(sMonitor);
   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);
   bool dispatchShutdownEvent;
   {
     ReentrantMonitorAutoEnter mon(*sMonitor);
     nsrefcnt count = --mRefCnt;
     NS_LOG_RELEASE(this, count, "SharedThreadPool");
     if (count) {
       return count;
     }
     // Zero refcount. Must shutdown and then delete the thread pool.
     // First, 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.
     RefPtr<nsIRunnable> r = NS_NewRunnableMethod(mPool, &nsIThreadPool::Shutdown);
     NS_DispatchToMainThread(r);
     // Remove SharedThreadPool from table of pools.
     sPools->Remove(mName);
     MOZ_ASSERT(!sPools->Get(mName));
     // Stabilize refcount, so that if something in the dtor QIs,
     // it won't explode.
     mRefCnt = 1;
     delete this;
     dispatchShutdownEvent = sPools->Count() == 0;
   }
   if (dispatchShutdownEvent) {
     // No more SharedThreadPools alive. Destroy the hash table.
     // Ensure that we only run on the main thread.
     // Do this in an event so that if something holds the monitor we won't
     // be deleting the monitor while it's held.
     NS_DispatchToMainThread(new ShutdownPoolsEvent(), NS_DISPATCH_NORMAL);
   }
   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);
 }
 #ifdef XP_WIN
 // Thread pool listener which ensures that MSCOM is initialized and
 // deinitialized on the thread pool thread. We may call into WMF or
 // DirectShow on this thread, so we need MSCOM working.
 class MSCOMInitThreadPoolListener MOZ_FINAL : public nsIThreadPoolListener {
 public:
   NS_DECL_THREADSAFE_ISUPPORTS
   NS_DECL_NSITHREADPOOLLISTENER
 };
 NS_IMPL_ISUPPORTS(MSCOMInitThreadPoolListener, nsIThreadPoolListener)
 NS_IMETHODIMP
 MSCOMInitThreadPoolListener::OnThreadCreated()
 {
   HRESULT hr = CoInitializeEx(0, COINIT_MULTITHREADED);
   if (FAILED(hr)) {
     NS_WARNING("Failed to initialize MSCOM on WMFByteStream thread.");
   }
   return NS_OK;
 }
 NS_IMETHODIMP
 MSCOMInitThreadPoolListener::OnThreadShuttingDown()
 {
   CoUninitialize();
   return NS_OK;
 }
 #endif // XP_WIN
 nsresult
 SharedThreadPool::EnsureThreadLimitIsAtLeast(uint32_t aLimit)
 {
   // We limit the number of threads that we use for media. 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)
 {
   MOZ_ASSERT(NS_IsMainThread());
   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(MEDIA_THREAD_STACK_SIZE);
   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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content/media/SharedThreadPool.cpp@44a2da4a2ab2 (annotated)

content/media/SharedThreadPool.cpp