1  /*
 2   * Copyright (C) 2017-2020 Apple Inc. All rights reserved.
 3   *
 4   * Redistribution and use in source and binary forms, with or without
 5   * modification, are permitted provided that the following conditions
 6   * are met:
 7   * 1. Redistributions of source code must retain the above copyright
 8   *    notice, this list of conditions and the following disclaimer.
 9   * 2. Redistributions in binary form must reproduce the above copyright
10   *    notice, this list of conditions and the following disclaimer in the
11   *    documentation and/or other materials provided with the distribution.
12   *
13   * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
17   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21   * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24   */
25  
26  #pragma once
27  
28  #include "JSRunLoopTimer.h"
29  #include "Strong.h"
30  
31  #include <wtf/Deque.h>
32  #include <wtf/HashMap.h>
33  #include <wtf/Lock.h>
34  #include <wtf/Vector.h>
35  
36  namespace JSC {
37  
38  class JSPromise;
39  class VM;
40  class JSCell;
41  
42  class JS_EXPORT_PRIVATE DeferredWorkTimer final : public JSRunLoopTimer {
43  public:
44      using Base = JSRunLoopTimer;
45  
46      void doWork(VM&) final;
47  
48      using Ticket = JSObject*;
49      void addPendingWork(VM&, Ticket, Vector<Strong<JSCell>>&& dependencies);
50      bool hasPendingWork(Ticket);
51      bool hasDependancyInPendingWork(Ticket, JSCell* dependency);
52      bool cancelPendingWork(Ticket);
53  
54      // If the script execution owner your ticket is associated with gets canceled
55      // the Task will not be called and will be deallocated. So it's important
56      // to make sure your memory ownership model won't leak memory when
57      // this occurs. The easiest way is to make sure everything is either owned
58      // by a GC'd value in dependencies or by the Task lambda.
59      using Task = Function<void()>;
60      void scheduleWorkSoon(Ticket, Task&&);
61      void didResumeScriptExecutionOwner();
62  
63      void stopRunningTasks() { m_runTasks = false; }
64      void runRunLoop();
65  
66      static Ref<DeferredWorkTimer> create(VM& vm) { return adoptRef(*new DeferredWorkTimer(vm)); }
67  private:
68      DeferredWorkTimer(VM&);
69  
70      Lock m_taskLock;
71      bool m_runTasks { true };
72      bool m_shouldStopRunLoopWhenAllTicketsFinish { false };
73      bool m_currentlyRunningTask { false };
74      Deque<std::tuple<Ticket, Task>> m_tasks;
75      struct TicketData {
76          Vector<Strong<JSCell>> dependencies;
77          Strong<JSObject> scriptExecutionOwner;
78      };
79      HashMap<Ticket, TicketData> m_pendingTickets;
80  };
81  
82  } // namespace JSC