зеркало из https://github.com/mozilla/gecko-dev.git
119 строки
4.6 KiB
C++
119 строки
4.6 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef SharedThreadPool_h_
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#define SharedThreadPool_h_
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#include <queue>
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#include "mozilla/RefPtr.h"
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#include "nsThreadUtils.h"
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#include "nsIThreadManager.h"
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#include "nsIThreadPool.h"
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#include "nsISupports.h"
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#include "nsISupportsImpl.h"
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#include "nsCOMPtr.h"
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namespace mozilla {
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// Wrapper that makes an nsIThreadPool a singleton, and provides a
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// consistent threadsafe interface to get instances. Callers simply get a
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// SharedThreadPool by the name of its nsIThreadPool. All get requests of
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// the same name get the same SharedThreadPool. Users must store a reference
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// to the pool, and when the last reference to a SharedThreadPool is dropped
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// the pool is shutdown and deleted. Users aren't required to manually
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// shutdown the pool, and can release references on any thread. This can make
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// it significantly easier to use thread pools, because the caller doesn't need
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// to worry about joining and tearing it down.
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//
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// On Windows all threads in the pool have MSCOM initialized with
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// COINIT_MULTITHREADED. Note that not all users of MSCOM use this mode see [1],
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// and mixing MSCOM objects between the two is terrible for performance, and can
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// cause some functions to fail. So be careful when using Win32 APIs on a
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// SharedThreadPool, and avoid sharing objects if at all possible.
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//
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// [1] http://mxr.mozilla.org/mozilla-central/search?string=coinitialize
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class SharedThreadPool : public nsIThreadPool
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{
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public:
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// Gets (possibly creating) the shared thread pool singleton instance with
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// thread pool named aName.
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static already_AddRefed<SharedThreadPool> Get(const nsCString& aName,
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uint32_t aThreadLimit = 4);
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// We implement custom threadsafe AddRef/Release pair, that destroys the
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// the shared pool singleton when the refcount drops to 0. The addref/release
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// are implemented using locking, so it's not recommended that you use them
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// in a tight loop.
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NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;
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NS_IMETHOD_(MozExternalRefCountType) AddRef(void) override;
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NS_IMETHOD_(MozExternalRefCountType) Release(void) override;
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// Forward behaviour to wrapped thread pool implementation.
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NS_FORWARD_SAFE_NSITHREADPOOL(mPool);
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NS_IMETHOD DispatchFromScript(nsIRunnable *event, uint32_t flags) override {
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return Dispatch(event, flags);
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}
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NS_IMETHOD Dispatch(already_AddRefed<nsIRunnable>&& event, uint32_t flags) override
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{ return !mEventTarget ? NS_ERROR_NULL_POINTER : mEventTarget->Dispatch(Move(event), flags); }
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using nsIEventTarget::Dispatch;
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NS_IMETHOD IsOnCurrentThread(bool *_retval) override { return !mEventTarget ? NS_ERROR_NULL_POINTER : mEventTarget->IsOnCurrentThread(_retval); }
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// Creates necessary statics. Called once at startup.
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static void InitStatics();
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// Spins the event loop until all thread pools are shutdown.
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// *Must* be called on the main thread.
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static void SpinUntilEmpty();
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#if defined(MOZ_ASAN)
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// Use the system default in ASAN builds, because the default is assumed to be
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// larger than the size we want to use and is hopefully sufficient for ASAN.
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static const uint32_t kStackSize = nsIThreadManager::DEFAULT_STACK_SIZE;
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#elif defined(XP_WIN) || defined(XP_MACOSX) || defined(LINUX)
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static const uint32_t kStackSize = (256 * 1024);
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#else
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// All other platforms use their system defaults.
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static const uint32_t kStackSize = nsIThreadManager::DEFAULT_STACK_SIZE;
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#endif
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private:
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// Returns whether there are no pools in existence at the moment.
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static bool IsEmpty();
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// Creates a singleton SharedThreadPool wrapper around aPool.
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// aName is the name of the aPool, and is used to lookup the
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// SharedThreadPool in the hash table of all created pools.
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SharedThreadPool(const nsCString& aName,
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nsIThreadPool* aPool);
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virtual ~SharedThreadPool();
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nsresult EnsureThreadLimitIsAtLeast(uint32_t aThreadLimit);
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// Name of mPool.
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const nsCString mName;
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// Thread pool being wrapped.
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nsCOMPtr<nsIThreadPool> mPool;
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// Refcount. We implement custom ref counting so that the thread pool is
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// shutdown in a threadsafe manner and singletonness is preserved.
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nsrefcnt mRefCnt;
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// mPool QI'd to nsIEventTarget. We cache this, so that we can use
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// NS_FORWARD_SAFE_NSIEVENTTARGET above.
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nsCOMPtr<nsIEventTarget> mEventTarget;
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};
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} // namespace mozilla
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#endif // SharedThreadPool_h_
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