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| 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/AbstractThread.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/AbstractThread.h')
| -rw-r--r-- | xpcom/threads/AbstractThread.h | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/xpcom/threads/AbstractThread.h b/xpcom/threads/AbstractThread.h new file mode 100644 index 0000000000..b53bcf8ca3 --- /dev/null +++ b/xpcom/threads/AbstractThread.h @@ -0,0 +1,129 @@ +/* -*- 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/. */ + +#if !defined(AbstractThread_h_) +# define AbstractThread_h_ + +# include "mozilla/AlreadyAddRefed.h" +# include "mozilla/ThreadLocal.h" +# include "nscore.h" +# include "nsISerialEventTarget.h" +# include "nsISupports.h" + +class nsIEventTarget; +class nsIRunnable; +class nsIThread; + +namespace mozilla { + +class TaskDispatcher; + +/* + * We often want to run tasks on a target that guarantees that events will never + * run in parallel. There are various target types that achieve this - namely + * nsIThread and TaskQueue. Note that nsIThreadPool (which implements + * nsIEventTarget) does not have this property, so we do not want to use + * nsIEventTarget for this purpose. This class encapsulates the specifics of + * the structures we might use here and provides a consistent interface. + * + * At present, the supported AbstractThread implementations are TaskQueue, + * AbstractThread::MainThread() and XPCOMThreadWrapper which can wrap any + * nsThread. + * + * The primary use of XPCOMThreadWrapper is to allow any threads to provide + * Direct Task dispatching which is similar (but not identical to) the microtask + * semantics of JS promises. Instantiating a XPCOMThreadWrapper on the current + * nsThread is sufficient to enable direct task dispatching. + * + * You shouldn't use pointers when comparing AbstractThread or nsIThread to + * determine if you are currently on the thread, but instead use the + * nsISerialEventTarget::IsOnCurrentThread() method. + */ +class AbstractThread : public nsISerialEventTarget { + public: + // Returns the AbstractThread that the caller is currently running in, or null + // if the caller is not running in an AbstractThread. + static AbstractThread* GetCurrent() { return sCurrentThreadTLS.get(); } + + AbstractThread(bool aSupportsTailDispatch) + : mSupportsTailDispatch(aSupportsTailDispatch) {} + + // We don't use NS_DECL_NSIEVENTTARGET so that we can remove the default + // |flags| parameter from Dispatch. Otherwise, a single-argument Dispatch call + // would be ambiguous. + using nsISerialEventTarget::IsOnCurrentThread; + NS_IMETHOD_(bool) IsOnCurrentThreadInfallible(void) override; + NS_IMETHOD IsOnCurrentThread(bool* _retval) override; + NS_IMETHOD Dispatch(already_AddRefed<nsIRunnable> event, + uint32_t flags) override; + NS_IMETHOD DispatchFromScript(nsIRunnable* event, uint32_t flags) override; + NS_IMETHOD DelayedDispatch(already_AddRefed<nsIRunnable> event, + uint32_t delay) override; + + enum DispatchReason { NormalDispatch, TailDispatch }; + virtual nsresult Dispatch(already_AddRefed<nsIRunnable> aRunnable, + DispatchReason aReason = NormalDispatch) = 0; + + virtual bool IsCurrentThreadIn() const = 0; + + // Returns a TaskDispatcher that will dispatch its tasks when the currently- + // running tasks pops off the stack. + // + // May only be called when running within the it is invoked up, and only on + // threads which support it. + virtual TaskDispatcher& TailDispatcher() = 0; + + // Returns true if we have tail tasks scheduled, or if this isn't known. + // Returns false if we definitely don't have any tail tasks. + virtual bool MightHaveTailTasks() { return true; } + + // Returns true if the tail dispatcher is available. In certain edge cases + // like shutdown, it might not be. + virtual bool IsTailDispatcherAvailable() { return true; } + + // Helper functions for methods on the tail TasklDispatcher. These check + // HasTailTasks to avoid allocating a TailDispatcher if it isn't + // needed. + nsresult TailDispatchTasksFor(AbstractThread* aThread); + bool HasTailTasksFor(AbstractThread* aThread); + + // Returns true if this supports the tail dispatcher. + bool SupportsTailDispatch() const { return mSupportsTailDispatch; } + + // Returns true if this thread requires all dispatches originating from + // aThread go through the tail dispatcher. + bool RequiresTailDispatch(AbstractThread* aThread) const; + bool RequiresTailDispatchFromCurrentThread() const; + + virtual nsIEventTarget* AsEventTarget() { MOZ_CRASH("Not an event target!"); } + + // Returns the non-DocGroup version of AbstractThread on the main thread. + // A DocGroup-versioned one is available in + // DispatcherTrait::AbstractThreadFor(). Note: + // DispatcherTrait::AbstractThreadFor() SHALL be used when possible. + static AbstractThread* MainThread(); + + // Must be called exactly once during startup. + static void InitTLS(); + static void InitMainThread(); + static void ShutdownMainThread(); + + void DispatchStateChange(already_AddRefed<nsIRunnable> aRunnable); + + static void DispatchDirectTask(already_AddRefed<nsIRunnable> aRunnable); + + protected: + virtual ~AbstractThread() = default; + static MOZ_THREAD_LOCAL(AbstractThread*) sCurrentThreadTLS; + + // True if we want to require that every task dispatched from tasks running in + // this queue go through our queue's tail dispatcher. + const bool mSupportsTailDispatch; +}; + +} // namespace mozilla + +#endif |