Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 1 | // Copyright 2015 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_CANCELABLE_TASK_H_ |
| 6 | #define V8_CANCELABLE_TASK_H_ |
| 7 | |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 8 | #include <map> |
| 9 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 10 | #include "include/v8-platform.h" |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 11 | #include "src/base/atomic-utils.h" |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 12 | #include "src/base/macros.h" |
| 13 | #include "src/base/platform/condition-variable.h" |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 14 | |
| 15 | namespace v8 { |
| 16 | namespace internal { |
| 17 | |
| 18 | class Cancelable; |
| 19 | class Isolate; |
| 20 | |
| 21 | |
| 22 | // Keeps track of cancelable tasks. It is possible to register and remove tasks |
| 23 | // from any fore- and background task/thread. |
| 24 | class CancelableTaskManager { |
| 25 | public: |
| 26 | CancelableTaskManager(); |
| 27 | |
| 28 | // Registers a new cancelable {task}. Returns the unique {id} of the task that |
| 29 | // can be used to try to abort a task by calling {Abort}. |
| 30 | uint32_t Register(Cancelable* task); |
| 31 | |
| 32 | // Try to abort running a task identified by {id}. The possible outcomes are: |
| 33 | // (1) The task is already finished running and thus has been removed from |
| 34 | // the manager. |
| 35 | // (2) The task is currently running and cannot be canceled anymore. |
| 36 | // (3) The task is not yet running (or finished) so it is canceled and |
| 37 | // removed. |
| 38 | // |
| 39 | // Returns {false} for (1) and (2), and {true} for (3). |
| 40 | bool TryAbort(uint32_t id); |
| 41 | |
| 42 | // Cancels all remaining registered tasks and waits for tasks that are |
| 43 | // already running. |
| 44 | void CancelAndWait(); |
| 45 | |
| 46 | private: |
| 47 | // Only called by {Cancelable} destructor. The task is done with executing, |
| 48 | // but needs to be removed. |
| 49 | void RemoveFinishedTask(uint32_t id); |
| 50 | |
| 51 | // To mitigate the ABA problem, the api refers to tasks through an id. |
| 52 | uint32_t task_id_counter_; |
| 53 | |
| 54 | // A set of cancelable tasks that are currently registered. |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 55 | std::map<uint32_t, Cancelable*> cancelable_tasks_; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 56 | |
| 57 | // Mutex and condition variable enabling concurrent register and removing, as |
| 58 | // well as waiting for background tasks on {CancelAndWait}. |
| 59 | base::ConditionVariable cancelable_tasks_barrier_; |
| 60 | base::Mutex mutex_; |
| 61 | |
| 62 | friend class Cancelable; |
| 63 | |
| 64 | DISALLOW_COPY_AND_ASSIGN(CancelableTaskManager); |
| 65 | }; |
| 66 | |
| 67 | |
| 68 | class Cancelable { |
| 69 | public: |
| 70 | explicit Cancelable(CancelableTaskManager* parent); |
| 71 | virtual ~Cancelable(); |
| 72 | |
| 73 | // Never invoke after handing over the task to the platform! The reason is |
| 74 | // that {Cancelable} is used in combination with {v8::Task} and handed to |
| 75 | // a platform. This step transfers ownership to the platform, which destroys |
| 76 | // the task after running it. Since the exact time is not known, we cannot |
| 77 | // access the object after handing it to a platform. |
| 78 | uint32_t id() { return id_; } |
| 79 | |
| 80 | protected: |
| 81 | bool TryRun() { return status_.TrySetValue(kWaiting, kRunning); } |
| 82 | bool IsRunning() { return status_.Value() == kRunning; } |
| 83 | intptr_t CancelAttempts() { return cancel_counter_.Value(); } |
| 84 | |
| 85 | private: |
| 86 | // Identifies the state a cancelable task is in: |
| 87 | // |kWaiting|: The task is scheduled and waiting to be executed. {TryRun} will |
| 88 | // succeed. |
| 89 | // |kCanceled|: The task has been canceled. {TryRun} will fail. |
| 90 | // |kRunning|: The task is currently running and cannot be canceled anymore. |
| 91 | enum Status { |
| 92 | kWaiting, |
| 93 | kCanceled, |
| 94 | kRunning, |
| 95 | }; |
| 96 | |
| 97 | // Use {CancelableTaskManager} to abort a task that has not yet been |
| 98 | // executed. |
| 99 | bool Cancel() { |
| 100 | if (status_.TrySetValue(kWaiting, kCanceled)) { |
| 101 | return true; |
| 102 | } |
| 103 | cancel_counter_.Increment(1); |
| 104 | return false; |
| 105 | } |
| 106 | |
| 107 | CancelableTaskManager* parent_; |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 108 | base::AtomicValue<Status> status_; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 109 | uint32_t id_; |
| 110 | |
| 111 | // The counter is incremented for failing tries to cancel a task. This can be |
| 112 | // used by the task itself as an indication how often external entities tried |
| 113 | // to abort it. |
Ben Murdoch | c561043 | 2016-08-08 18:44:38 +0100 | [diff] [blame] | 114 | base::AtomicNumber<intptr_t> cancel_counter_; |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 115 | |
| 116 | friend class CancelableTaskManager; |
| 117 | |
| 118 | DISALLOW_COPY_AND_ASSIGN(Cancelable); |
| 119 | }; |
| 120 | |
| 121 | |
| 122 | // Multiple inheritance can be used because Task is a pure interface. |
| 123 | class CancelableTask : public Cancelable, public Task { |
| 124 | public: |
| 125 | explicit CancelableTask(Isolate* isolate); |
| 126 | |
| 127 | // Task overrides. |
| 128 | void Run() final { |
| 129 | if (TryRun()) { |
| 130 | RunInternal(); |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | virtual void RunInternal() = 0; |
| 135 | |
| 136 | Isolate* isolate() { return isolate_; } |
| 137 | |
| 138 | private: |
| 139 | Isolate* isolate_; |
| 140 | DISALLOW_COPY_AND_ASSIGN(CancelableTask); |
| 141 | }; |
| 142 | |
| 143 | |
| 144 | // Multiple inheritance can be used because IdleTask is a pure interface. |
| 145 | class CancelableIdleTask : public Cancelable, public IdleTask { |
| 146 | public: |
| 147 | explicit CancelableIdleTask(Isolate* isolate); |
| 148 | |
| 149 | // IdleTask overrides. |
| 150 | void Run(double deadline_in_seconds) final { |
| 151 | if (TryRun()) { |
| 152 | RunInternal(deadline_in_seconds); |
| 153 | } |
| 154 | } |
| 155 | |
| 156 | virtual void RunInternal(double deadline_in_seconds) = 0; |
| 157 | |
| 158 | Isolate* isolate() { return isolate_; } |
| 159 | |
| 160 | private: |
| 161 | Isolate* isolate_; |
| 162 | DISALLOW_COPY_AND_ASSIGN(CancelableIdleTask); |
| 163 | }; |
| 164 | |
| 165 | |
| 166 | } // namespace internal |
| 167 | } // namespace v8 |
| 168 | |
| 169 | #endif // V8_CANCELABLE_TASK_H_ |