gecko-dev/dom/workers/WorkerRunnable.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_dom_workers_workerrunnable_h__
#define mozilla_dom_workers_workerrunnable_h__
#include "Workers.h"
#include "nsICancelableRunnable.h"
#include "mozilla/Atomics.h"
#include "nsISupportsImpl.h"
#include "nsThreadUtils.h" /* nsRunnable */
struct JSContext;
class nsIEventTarget;
namespace mozilla {
class ErrorResult;
} // namespace mozilla
BEGIN_WORKERS_NAMESPACE
class WorkerPrivate;
// Use this runnable to communicate from the worker to its parent or vice-versa.
// The busy count must be taken into consideration and declared at construction
// time.
class WorkerRunnable : public nsIRunnable,
public nsICancelableRunnable
{
public:
enum TargetAndBusyBehavior {
// Target the main thread for top-level workers, otherwise target the
// WorkerThread of the worker's parent. No change to the busy count.
ParentThreadUnchangedBusyCount,
// Target the thread where the worker event loop runs. The busy count will
// be incremented before dispatching and decremented (asynchronously) after
// running.
WorkerThreadModifyBusyCount,
// Target the thread where the worker event loop runs. The busy count will
// not be modified in any way. Besides worker-internal runnables this is
// almost always the wrong choice.
WorkerThreadUnchangedBusyCount
};
protected:
// The WorkerPrivate that this runnable is associated with.
WorkerPrivate* mWorkerPrivate;
// See above.
TargetAndBusyBehavior mBehavior;
// It's unclear whether or not Cancel() is supposed to work when called on any
// thread. To be safe we're using an atomic but it's likely overkill.
Atomic<uint32_t> mCanceled;
private:
// Whether or not Cancel() is currently being called from inside the Run()
// method. Avoids infinite recursion when a subclass calls Run() from inside
// Cancel(). Only checked and modified on the target thread.
bool mCallingCancelWithinRun;
public:
NS_DECL_THREADSAFE_ISUPPORTS
// If you override Cancel() then you'll need to either call the base class
// Cancel() method or override IsCanceled() so that the Run() method bails out
// appropriately.
nsresult
Cancel() override;
// The return value is true if and only if both PreDispatch and
// DispatchInternal return true.
bool
Dispatch();
// See above note about Cancel().
virtual bool
IsCanceled() const
{
return mCanceled != 0;
}
static WorkerRunnable*
FromRunnable(nsIRunnable* aRunnable);
protected:
WorkerRunnable(WorkerPrivate* aWorkerPrivate,
TargetAndBusyBehavior aBehavior = WorkerThreadModifyBusyCount)
#ifdef DEBUG
;
#else
: mWorkerPrivate(aWorkerPrivate), mBehavior(aBehavior), mCanceled(0),
mCallingCancelWithinRun(false)
{ }
#endif
// This class is reference counted.
virtual ~WorkerRunnable()
{ }
// Returns true if this runnable should be dispatched to the debugger queue,
// and false otherwise.
virtual bool
IsDebuggerRunnable() const;
nsIGlobalObject*
DefaultGlobalObject() const;
// By default asserts that Dispatch() is being called on the right thread
// (ParentThread if |mTarget| is WorkerThread, or WorkerThread otherwise).
// Also increments the busy count of |mWorkerPrivate| if targeting the
// WorkerThread.
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate);
// By default asserts that Dispatch() is being called on the right thread
// (ParentThread if |mTarget| is WorkerThread, or WorkerThread otherwise).
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult);
// May be implemented by subclasses if desired if they need to do some sort of
// setup before we try to set up our JSContext and compartment for real.
// Typically the only thing that should go in here is creation of the worker's
// global.
//
// If false is returned, WorkerRun will not be called at all. PostRun will
// still be called, with false passed for aRunResult.
virtual bool
PreRun(WorkerPrivate* aWorkerPrivate);
// Must be implemented by subclasses. Called on the target thread. The return
// value will be passed to PostRun(). The JSContext passed in here comes from
// an AutoJSAPI (or AutoEntryScript) that we set up on the stack. If
// mBehavior is ParentThreadUnchangedBusyCount, it is in the compartment of
// mWorkerPrivate's reflector (i.e. the worker object in the parent thread),
// unless that reflector is null, in which case it's in the compartment of the
// parent global (which is the compartment reflector would have been in), or
// in the null compartment if there is no parent global. For other mBehavior
// values, we're running on the worker thread and aCx is in whatever
// compartment GetCurrentThreadJSContext() was in when nsIRunnable::Run() got
// called. This is actually important for cases when a runnable spins a
// syncloop and wants everything that happens during the syncloop to happen in
// the compartment that runnable set up (which may, for example, be a debugger
// sandbox compartment!). If aCx wasn't in a compartment to start with, aCx
// will be in either the debugger global's compartment or the worker's
// global's compartment depending on whether IsDebuggerRunnable() is true.
//
// Immediately after WorkerRun returns, the caller will assert that either it
// returns false or there is no exception pending on aCx. Then it will report
// any pending exceptions on aCx.
virtual bool
WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) = 0;
// By default asserts that Run() (and WorkerRun()) were called on the correct
// thread. Also sends an asynchronous message to the ParentThread if the
// busy count was previously modified in PreDispatch().
//
// The aCx passed here is the same one as was passed to WorkerRun and is
// still in the same compartment. PostRun implementations must NOT leave an
// exception on the JSContext and must not run script, because the incoming
// JSContext may be in the null compartment.
virtual void
PostRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate, bool aRunResult);
virtual bool
DispatchInternal();
// Calling Run() directly is not supported. Just call Dispatch() and
// WorkerRun() will be called on the correct thread automatically.
NS_DECL_NSIRUNNABLE
};
// This runnable is used to send a message to a worker debugger.
class WorkerDebuggerRunnable : public WorkerRunnable
{
protected:
explicit WorkerDebuggerRunnable(WorkerPrivate* aWorkerPrivate)
: WorkerRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount)
{
}
virtual ~WorkerDebuggerRunnable()
{ }
private:
virtual bool
IsDebuggerRunnable() const override
{
return true;
}
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate) override final
{
AssertIsOnMainThread();
return true;
}
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult) override;
};
// This runnable is used to send a message directly to a worker's sync loop.
class WorkerSyncRunnable : public WorkerRunnable
{
protected:
nsCOMPtr<nsIEventTarget> mSyncLoopTarget;
// Passing null for aSyncLoopTarget is allowed and will result in the behavior
// of a normal WorkerRunnable.
WorkerSyncRunnable(WorkerPrivate* aWorkerPrivate,
nsIEventTarget* aSyncLoopTarget);
WorkerSyncRunnable(WorkerPrivate* aWorkerPrivate,
already_AddRefed<nsIEventTarget>&& aSyncLoopTarget);
virtual ~WorkerSyncRunnable();
virtual bool
DispatchInternal() override;
};
// This runnable is identical to WorkerSyncRunnable except it is meant to be
// created on and dispatched from the main thread only. Its WorkerRun/PostRun
// will run on the worker thread.
class MainThreadWorkerSyncRunnable : public WorkerSyncRunnable
{
protected:
// Passing null for aSyncLoopTarget is allowed and will result in the behavior
// of a normal WorkerRunnable.
MainThreadWorkerSyncRunnable(WorkerPrivate* aWorkerPrivate,
nsIEventTarget* aSyncLoopTarget)
: WorkerSyncRunnable(aWorkerPrivate, aSyncLoopTarget)
{
AssertIsOnMainThread();
}
MainThreadWorkerSyncRunnable(WorkerPrivate* aWorkerPrivate,
already_AddRefed<nsIEventTarget>&& aSyncLoopTarget)
: WorkerSyncRunnable(aWorkerPrivate, Move(aSyncLoopTarget))
{
AssertIsOnMainThread();
}
virtual ~MainThreadWorkerSyncRunnable()
{ }
private:
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate) override
{
AssertIsOnMainThread();
return true;
}
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult) override;
};
// This runnable is processed as soon as it is received by the worker,
// potentially running before previously queued runnables and perhaps even with
// other JS code executing on the stack. These runnables must not alter the
// state of the JS runtime and should only twiddle state values. The busy count
// is never modified.
class WorkerControlRunnable : public WorkerRunnable
{
friend class WorkerPrivate;
protected:
WorkerControlRunnable(WorkerPrivate* aWorkerPrivate,
TargetAndBusyBehavior aBehavior = WorkerThreadModifyBusyCount)
#ifdef DEBUG
;
#else
: WorkerRunnable(aWorkerPrivate, aBehavior)
{ }
#endif
virtual ~WorkerControlRunnable()
{ }
nsresult
Cancel() override;
public:
NS_DECL_ISUPPORTS_INHERITED
private:
virtual bool
DispatchInternal() override;
// Should only be called by WorkerPrivate::DoRunLoop.
using WorkerRunnable::Cancel;
};
// A convenience class for WorkerRunnables that are originated on the main
// thread.
class MainThreadWorkerRunnable : public WorkerRunnable
{
protected:
explicit MainThreadWorkerRunnable(WorkerPrivate* aWorkerPrivate)
: WorkerRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount)
{
AssertIsOnMainThread();
}
virtual ~MainThreadWorkerRunnable()
{}
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate) override
{
AssertIsOnMainThread();
return true;
}
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate,
bool aDispatchResult) override
{
AssertIsOnMainThread();
}
};
// A convenience class for WorkerControlRunnables that originate on the main
// thread.
class MainThreadWorkerControlRunnable : public WorkerControlRunnable
{
protected:
explicit MainThreadWorkerControlRunnable(WorkerPrivate* aWorkerPrivate)
: WorkerControlRunnable(aWorkerPrivate, WorkerThreadUnchangedBusyCount)
{ }
virtual ~MainThreadWorkerControlRunnable()
{ }
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate) override
{
AssertIsOnMainThread();
return true;
}
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult) override
{
AssertIsOnMainThread();
}
};
// A WorkerRunnable that should be dispatched from the worker to itself for
// async tasks. This will increment the busy count PostDispatch() (only if
// dispatch was successful) and decrement it in PostRun().
//
// Async tasks will almost always want to use this since
// a WorkerSameThreadRunnable keeps the Worker from being GCed.
class WorkerSameThreadRunnable : public WorkerRunnable
{
protected:
explicit WorkerSameThreadRunnable(WorkerPrivate* aWorkerPrivate)
: WorkerRunnable(aWorkerPrivate, WorkerThreadModifyBusyCount)
{ }
virtual ~WorkerSameThreadRunnable()
{ }
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate) override;
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult) override;
// We just delegate PostRun to WorkerRunnable, since it does exactly
// what we want.
};
// Base class for the runnable objects, which makes a synchronous call to
// dispatch the tasks from the worker thread to the main thread.
//
// Note that the derived class must override MainThreadRun.
class WorkerMainThreadRunnable : public Runnable
{
protected:
WorkerPrivate* mWorkerPrivate;
nsCOMPtr<nsIEventTarget> mSyncLoopTarget;
const nsCString mTelemetryKey;
explicit WorkerMainThreadRunnable(WorkerPrivate* aWorkerPrivate,
const nsACString& aTelemetryKey);
~WorkerMainThreadRunnable() {}
virtual bool MainThreadRun() = 0;
public:
// Dispatch the runnable to the main thread. If dispatch to main thread
// fails, or if the worker is in a state equal or greater of aFailStatus, an
// error will be reported on aRv. Normally you want to use 'Terminating' for
// aFailStatus, except if you want an infallible runnable. In this case, use
// 'Killing'.
// In that case the error MUST be propagated out to script.
void Dispatch(Status aFailStatus, ErrorResult& aRv);
private:
NS_IMETHOD Run() override;
};
// This runnable is an helper class for dispatching something from a worker
// thread to the main-thread and back to the worker-thread. During this
// operation, this class will keep the worker alive.
class WorkerProxyToMainThreadRunnable : public Runnable
{
protected:
explicit WorkerProxyToMainThreadRunnable(WorkerPrivate* aWorkerPrivate);
virtual ~WorkerProxyToMainThreadRunnable();
// First this method is called on the main-thread.
virtual void RunOnMainThread() = 0;
// After this second method is called on the worker-thread.
virtual void RunBackOnWorkerThread() = 0;
public:
bool Dispatch();
private:
NS_IMETHOD Run() override;
void PostDispatchOnMainThread();
bool HoldWorker();
void ReleaseWorker();
protected:
WorkerPrivate* mWorkerPrivate;
UniquePtr<WorkerHolder> mWorkerHolder;
};
// Class for checking API exposure. This totally violates the "MUST" in the
// comments on WorkerMainThreadRunnable::Dispatch, because API exposure checks
// can't throw. Maybe we should change it so they _could_ throw. But for now
// we are bad people and should be ashamed of ourselves. Let's hope none of
// them happen while a worker is shutting down.
//
// Do NOT copy what this class is doing elsewhere. Just don't.
class WorkerCheckAPIExposureOnMainThreadRunnable
: public WorkerMainThreadRunnable
{
public:
explicit
WorkerCheckAPIExposureOnMainThreadRunnable(WorkerPrivate* aWorkerPrivate);
virtual
~WorkerCheckAPIExposureOnMainThreadRunnable();
// Returns whether the dispatch succeeded. If this returns false, the API
// should not be exposed.
bool Dispatch();
};
// This runnable is used to stop a sync loop and it's meant to be used on the
// main-thread only. As sync loops keep the busy count incremented as long as
// they run this runnable does not modify the busy count
// in any way.
class MainThreadStopSyncLoopRunnable : public WorkerSyncRunnable
{
bool mResult;
public:
// Passing null for aSyncLoopTarget is not allowed.
MainThreadStopSyncLoopRunnable(
WorkerPrivate* aWorkerPrivate,
already_AddRefed<nsIEventTarget>&& aSyncLoopTarget,
bool aResult);
// By default StopSyncLoopRunnables cannot be canceled since they could leave
// a sync loop spinning forever.
nsresult
Cancel() override;
protected:
virtual ~MainThreadStopSyncLoopRunnable()
{ }
private:
virtual bool
PreDispatch(WorkerPrivate* aWorkerPrivate) override final
{
AssertIsOnMainThread();
return true;
}
virtual void
PostDispatch(WorkerPrivate* aWorkerPrivate, bool aDispatchResult) override;
virtual bool
WorkerRun(JSContext* aCx, WorkerPrivate* aWorkerPrivate) override;
virtual bool
DispatchInternal() override final;
};
END_WORKERS_NAMESPACE
#endif // mozilla_dom_workers_workerrunnable_h__