diff options
| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 19:33:14 +0000 |
| commit | 36d22d82aa202bb199967e9512281e9a53db42c9 (patch) | |
| tree | 105e8c98ddea1c1e4784a60a5a6410fa416be2de /xpcom/threads/SharedThreadPool.h | |
| parent | Initial commit. (diff) | |
| download | firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.tar.xz firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.zip | |
Adding upstream version 115.7.0esr.upstream/115.7.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'xpcom/threads/SharedThreadPool.h')
| -rw-r--r-- | xpcom/threads/SharedThreadPool.h | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/xpcom/threads/SharedThreadPool.h b/xpcom/threads/SharedThreadPool.h new file mode 100644 index 0000000000..5c29ba11f2 --- /dev/null +++ b/xpcom/threads/SharedThreadPool.h @@ -0,0 +1,130 @@ +/* -*- 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/. */ + +#ifndef SharedThreadPool_h_ +#define SharedThreadPool_h_ + +#include <utility> +#include "mozilla/AlreadyAddRefed.h" +#include "mozilla/RefCountType.h" +#include "nsCOMPtr.h" +#include "nsID.h" +#include "nsIThreadPool.h" +#include "nsString.h" +#include "nscore.h" + +class nsIRunnable; + +namespace mozilla { + +// Wrapper that makes an nsIThreadPool a singleton, and provides a +// consistent threadsafe interface to get instances. Callers simply get a +// SharedThreadPool by the name of its nsIThreadPool. All get requests of +// the same name get the same SharedThreadPool. Users must store a reference +// to the pool, and when the last reference to a SharedThreadPool is dropped +// the pool is shutdown and deleted. Users aren't required to manually +// shutdown the pool, and can release references on any thread. This can make +// it significantly easier to use thread pools, because the caller doesn't need +// to worry about joining and tearing it down. +// +// On Windows all threads in the pool have MSCOM initialized with +// COINIT_MULTITHREADED. Note that not all users of MSCOM use this mode see [1], +// and mixing MSCOM objects between the two is terrible for performance, and can +// cause some functions to fail. So be careful when using Win32 APIs on a +// SharedThreadPool, and avoid sharing objects if at all possible. +// +// [1] +// https://searchfox.org/mozilla-central/search?q=coinitialize&redirect=false +class SharedThreadPool : public nsIThreadPool { + public: + // Gets (possibly creating) the shared thread pool singleton instance with + // thread pool named aName. + static already_AddRefed<SharedThreadPool> Get(const nsCString& aName, + uint32_t aThreadLimit = 4); + + // We implement custom threadsafe AddRef/Release pair, that destroys the + // the shared pool singleton when the refcount drops to 0. The addref/release + // are implemented using locking, so it's not recommended that you use them + // in a tight loop. + NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override; + NS_IMETHOD_(MozExternalRefCountType) AddRef(void) override; + NS_IMETHOD_(MozExternalRefCountType) Release(void) override; + + // Forward behaviour to wrapped thread pool implementation. + NS_FORWARD_SAFE_NSITHREADPOOL(mPool); + + // Call this when dispatching from an event on the same + // threadpool that is about to complete. We should not create a new thread + // in that case since a thread is about to become idle. + nsresult DispatchFromEndOfTaskInThisPool(nsIRunnable* event) { + return Dispatch(event, NS_DISPATCH_AT_END); + } + + NS_IMETHOD DispatchFromScript(nsIRunnable* event, uint32_t flags) override { + return Dispatch(event, flags); + } + + NS_IMETHOD Dispatch(already_AddRefed<nsIRunnable> event, + uint32_t flags = NS_DISPATCH_NORMAL) override { + return !mPool ? NS_ERROR_NULL_POINTER + : mPool->Dispatch(std::move(event), flags); + } + + NS_IMETHOD DelayedDispatch(already_AddRefed<nsIRunnable>, uint32_t) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + + using nsIEventTarget::Dispatch; + + NS_IMETHOD RegisterShutdownTask(nsITargetShutdownTask* task) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + + NS_IMETHOD UnregisterShutdownTask(nsITargetShutdownTask* task) override { + return NS_ERROR_NOT_IMPLEMENTED; + } + + NS_IMETHOD IsOnCurrentThread(bool* _retval) override { + return !mPool ? NS_ERROR_NULL_POINTER : mPool->IsOnCurrentThread(_retval); + } + + NS_IMETHOD_(bool) IsOnCurrentThreadInfallible() override { + return mPool && mPool->IsOnCurrentThread(); + } + + // Creates necessary statics. Called once at startup. + static void InitStatics(); + + // Spins the event loop until all thread pools are shutdown. + // *Must* be called on the main thread. + static void SpinUntilEmpty(); + + private: + // Returns whether there are no pools in existence at the moment. + static bool IsEmpty(); + + // Creates a singleton SharedThreadPool wrapper around aPool. + // aName is the name of the aPool, and is used to lookup the + // SharedThreadPool in the hash table of all created pools. + SharedThreadPool(const nsCString& aName, nsIThreadPool* aPool); + virtual ~SharedThreadPool(); + + nsresult EnsureThreadLimitIsAtLeast(uint32_t aThreadLimit); + + // Name of mPool. + const nsCString mName; + + // Thread pool being wrapped. + nsCOMPtr<nsIThreadPool> mPool; + + // Refcount. We implement custom ref counting so that the thread pool is + // shutdown in a threadsafe manner and singletonness is preserved. + nsrefcnt mRefCnt; +}; + +} // namespace mozilla + +#endif // SharedThreadPool_h_ |