gecko-dev/xpcom/threads/Dispatcher.h

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/* -*- 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 mozilla_Dispatcher_h
#define mozilla_Dispatcher_h
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/TaskCategory.h"
#include "nsCOMPtr.h"
#include "nsISupportsImpl.h"
class nsIEventTarget;
class nsIRunnable;
namespace mozilla {
class AbstractThread;
namespace dom {
class TabGroup;
}
// The "main thread" in Gecko will soon be a set of cooperatively scheduled
// "fibers". Global state in Gecko will be partitioned into a series of "groups"
// (with roughly one group per tab). Runnables will be annotated with the set of
// groups that they touch. Two runnables may run concurrently on different
// fibers as long as they touch different groups.
//
// A Dispatcher is an abstract class to represent a "group". Essentially the
// only functionality offered by a Dispatcher is the ability to dispatch
// runnables to the group. TabGroup, DocGroup, and SystemGroup are the concrete
// implementations of Dispatcher.
class Dispatcher
{
public:
NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
// Implementations of this method must be safe to call off the main thread.
virtual nsresult Dispatch(const char* aName,
TaskCategory aCategory,
already_AddRefed<nsIRunnable>&& aRunnable) = 0;
// Implementations of this method must be safe to call off the main thread.
// The returned nsIEventTarget must also be usable from any thread.
virtual nsIEventTarget* EventTargetFor(TaskCategory aCategory) const = 0;
// Must always be called on the main thread. The returned AbstractThread can
// always be used off the main thread.
AbstractThread* AbstractMainThreadFor(TaskCategory aCategory);
// This method performs a safe cast. It returns null if |this| is not of the
// requested type.
virtual dom::TabGroup* AsTabGroup() { return nullptr; }
static nsresult UnlabeledDispatch(const char* aName,
TaskCategory aCategory,
already_AddRefed<nsIRunnable>&& aRunnable);
protected:
// Implementations are guaranteed that this method is called on the main
// thread.
virtual AbstractThread* AbstractMainThreadForImpl(TaskCategory aCategory) = 0;
};
class ValidatingDispatcher : public Dispatcher
{
public:
ValidatingDispatcher();
class MOZ_STACK_CLASS AutoProcessEvent final {
public:
AutoProcessEvent();
~AutoProcessEvent();
private:
ValidatingDispatcher* mPrevRunningDispatcher;
};
// Ensure that it's valid to access the TabGroup at this time.
void ValidateAccess() const
{
MOZ_ASSERT(!sRunningDispatcher || mAccessValid);
}
class Runnable;
friend class Runnable;
bool* GetValidAccessPtr() { return &mAccessValid; }
nsresult Dispatch(const char* aName,
TaskCategory aCategory,
already_AddRefed<nsIRunnable>&& aRunnable) override;
nsIEventTarget* EventTargetFor(TaskCategory aCategory) const override;
protected:
// Implementations are guaranteed that this method is called on the main
// thread.
AbstractThread* AbstractMainThreadForImpl(TaskCategory aCategory) override;
// Helper method to create an event target specific to a particular TaskCategory.
virtual already_AddRefed<nsIEventTarget>
CreateEventTargetFor(TaskCategory aCategory);
// Given an event target returned by |dispatcher->CreateEventTargetFor|, this
// function returns |dispatcher|.
static ValidatingDispatcher* FromEventTarget(nsIEventTarget* aEventTarget);
nsresult LabeledDispatch(const char* aName,
TaskCategory aCategory,
already_AddRefed<nsIRunnable>&& aRunnable);
void CreateEventTargets(bool aNeedValidation);
// Shuts down this dispatcher. If aXPCOMShutdown is true, invalidates this
// dispatcher.
void Shutdown(bool aXPCOMShutdown);
enum ValidationType {
StartValidation,
EndValidation,
};
void SetValidatingAccess(ValidationType aType);
static ValidatingDispatcher* sRunningDispatcher;
bool mAccessValid;
nsCOMPtr<nsIEventTarget> mEventTargets[size_t(TaskCategory::Count)];
RefPtr<AbstractThread> mAbstractThreads[size_t(TaskCategory::Count)];
};
} // namespace mozilla
#endif // mozilla_dom_Dispatcher_h