1 // Copyright 2016 The Chromium Authors 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 BASE_TASK_THREAD_POOL_THREAD_POOL_IMPL_H_ 6 #define BASE_TASK_THREAD_POOL_THREAD_POOL_IMPL_H_ 7 8 #include <memory> 9 #include <optional> 10 #include <string_view> 11 12 #include "base/base_export.h" 13 #include "base/dcheck_is_on.h" 14 #include "base/functional/callback.h" 15 #include "base/memory/ptr_util.h" 16 #include "base/sequence_checker.h" 17 #include "base/synchronization/atomic_flag.h" 18 #include "base/task/single_thread_task_runner_thread_mode.h" 19 #include "base/task/task_traits.h" 20 #include "base/task/thread_pool/delayed_task_manager.h" 21 #include "base/task/thread_pool/environment_config.h" 22 #include "base/task/thread_pool/pooled_single_thread_task_runner_manager.h" 23 #include "base/task/thread_pool/pooled_task_runner_delegate.h" 24 #include "base/task/thread_pool/service_thread.h" 25 #include "base/task/thread_pool/task_source.h" 26 #include "base/task/thread_pool/task_tracker.h" 27 #include "base/task/thread_pool/thread_group.h" 28 #include "base/task/thread_pool/thread_pool_instance.h" 29 #include "base/task/updateable_sequenced_task_runner.h" 30 #include "base/thread_annotations.h" 31 #include "build/build_config.h" 32 33 #if BUILDFLAG(IS_WIN) 34 #include "base/win/com_init_check_hook.h" 35 #endif 36 37 namespace base { 38 39 namespace internal { 40 41 // Default ThreadPoolInstance implementation. This class is thread-safe, except 42 // for methods noted otherwise in thread_pool_instance.h. 43 class BASE_EXPORT ThreadPoolImpl : public ThreadPoolInstance, 44 public ThreadGroup::Delegate, 45 public PooledTaskRunnerDelegate { 46 public: 47 using TaskTrackerImpl = TaskTracker; 48 49 // Creates a ThreadPoolImpl with a production TaskTracker. |histogram_label| 50 // is used to label histograms. No histograms are recorded if it is empty. 51 explicit ThreadPoolImpl(std::string_view histogram_label); 52 53 // For testing only. Creates a ThreadPoolImpl with a custom TaskTracker. 54 // If |!use_background_threads|, background threads will run with default 55 // priority. 56 ThreadPoolImpl(std::string_view histogram_label, 57 std::unique_ptr<TaskTrackerImpl> task_tracker, 58 bool use_background_threads = true); 59 60 ThreadPoolImpl(const ThreadPoolImpl&) = delete; 61 ThreadPoolImpl& operator=(const ThreadPoolImpl&) = delete; 62 ~ThreadPoolImpl() override; 63 64 // ThreadPoolInstance: 65 void Start(const ThreadPoolInstance::InitParams& init_params, 66 WorkerThreadObserver* worker_thread_observer) override; 67 bool WasStarted() const final; 68 bool WasStartedUnsafe() const final; 69 size_t GetMaxConcurrentNonBlockedTasksWithTraitsDeprecated( 70 const TaskTraits& traits) const override; 71 void Shutdown() override; 72 void FlushForTesting() override; 73 void FlushAsyncForTesting(OnceClosure flush_callback) override; 74 void JoinForTesting() override; 75 void BeginFence() override; 76 void EndFence() override; 77 void BeginBestEffortFence() override; 78 void EndBestEffortFence() override; 79 void BeginRestrictedTasks() override; 80 void EndRestrictedTasks() override; 81 void BeginFizzlingBlockShutdownTasks() override; 82 void EndFizzlingBlockShutdownTasks() override; 83 84 // PooledTaskRunnerDelegate: 85 bool EnqueueJobTaskSource(scoped_refptr<JobTaskSource> task_source) override; 86 void RemoveJobTaskSource(scoped_refptr<JobTaskSource> task_source) override; 87 void UpdatePriority(scoped_refptr<TaskSource> task_source, 88 TaskPriority priority) override; 89 void UpdateJobPriority(scoped_refptr<TaskSource> task_source, 90 TaskPriority priority) override; 91 92 // Returns the TimeTicks of the next task scheduled on ThreadPool (Now() if 93 // immediate, nullopt if none). This is thread-safe, i.e., it's safe if tasks 94 // are being posted in parallel with this call but such a situation obviously 95 // results in a race as to whether this call will see the new tasks in time. 96 std::optional<TimeTicks> NextScheduledRunTimeForTesting() const; 97 98 // Forces ripe delayed tasks to be posted (e.g. when time is mocked and 99 // advances faster than the real-time delay on ServiceThread). 100 void ProcessRipeDelayedTasksForTesting(); 101 102 // Requests that all threads started by future ThreadPoolImpls in this process 103 // have a synchronous start (if |enabled|; cancels this behavior otherwise). 104 // Must be called while no ThreadPoolImpls are alive in this process. This is 105 // exposed here on this internal API rather than as a ThreadPoolInstance 106 // configuration param because only one internal test truly needs this. 107 static void SetSynchronousThreadStartForTesting(bool enabled); 108 109 // Posts |task| with a |delay| and specific |traits|. |delay| can be zero. For 110 // one off tasks that don't require a TaskRunner. Returns false if the task 111 // definitely won't run because of current shutdown state. 112 bool PostDelayedTask(const Location& from_here, 113 const TaskTraits& traits, 114 OnceClosure task, 115 TimeDelta delay); 116 117 // Returns a TaskRunner whose PostTask invocations result in scheduling tasks 118 // using |traits|. Tasks may run in any order and in parallel. 119 scoped_refptr<TaskRunner> CreateTaskRunner(const TaskTraits& traits); 120 121 // Returns a SequencedTaskRunner whose PostTask invocations result in 122 // scheduling tasks using |traits|. Tasks run one at a time in posting order. 123 scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunner( 124 const TaskTraits& traits); 125 126 // Returns a SingleThreadTaskRunner whose PostTask invocations result in 127 // scheduling tasks using |traits|. Tasks run on a single thread in posting 128 // order. If |traits| identifies an existing thread, 129 // SingleThreadTaskRunnerThreadMode::SHARED must be used. 130 scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunner( 131 const TaskTraits& traits, 132 SingleThreadTaskRunnerThreadMode thread_mode); 133 134 #if BUILDFLAG(IS_WIN) 135 // Returns a SingleThreadTaskRunner whose PostTask invocations result in 136 // scheduling tasks using |traits| in a COM Single-Threaded Apartment. Tasks 137 // run in the same Single-Threaded Apartment in posting order for the returned 138 // SingleThreadTaskRunner. If |traits| identifies an existing thread, 139 // SingleThreadTaskRunnerThreadMode::SHARED must be used. 140 scoped_refptr<SingleThreadTaskRunner> CreateCOMSTATaskRunner( 141 const TaskTraits& traits, 142 SingleThreadTaskRunnerThreadMode thread_mode); 143 #endif // BUILDFLAG(IS_WIN) 144 145 // Returns a task runner whose PostTask invocations result in scheduling tasks 146 // using |traits|. The priority in |traits| can be updated at any time via 147 // UpdateableSequencedTaskRunner::UpdatePriority(). An update affects all 148 // tasks posted to the task runner that aren't running yet. Tasks run one at a 149 // time in posting order. 150 // 151 // |traits| requirements: 152 // - base::ThreadPolicy must be specified if the priority of the task runner 153 // will ever be increased from BEST_EFFORT. 154 scoped_refptr<UpdateableSequencedTaskRunner> 155 CreateUpdateableSequencedTaskRunner(const TaskTraits& traits); 156 157 private: 158 // Invoked after |num_fences_| or |num_best_effort_fences_| is updated. Sets 159 // the CanRunPolicy in TaskTracker and wakes up workers as appropriate. 160 void UpdateCanRunPolicy(); 161 162 const ThreadGroup* GetThreadGroupForTraits(const TaskTraits& traits) const; 163 164 // ThreadGroup::Delegate: 165 ThreadGroup* GetThreadGroupForTraits(const TaskTraits& traits) override; 166 167 // Posts |task| to be executed by the appropriate thread group as part of 168 // |sequence|. This must only be called after |task| has gone through 169 // TaskTracker::WillPostTask() and after |task|'s delayed run time. 170 bool PostTaskWithSequenceNow(Task task, scoped_refptr<Sequence> sequence); 171 172 // PooledTaskRunnerDelegate: 173 bool PostTaskWithSequence(Task task, 174 scoped_refptr<Sequence> sequence) override; 175 bool ShouldYield(const TaskSource* task_source) override; 176 177 const std::string histogram_label_; 178 const std::unique_ptr<TaskTrackerImpl> task_tracker_; 179 const bool use_background_threads_; 180 ServiceThread service_thread_; 181 DelayedTaskManager delayed_task_manager_; 182 PooledSingleThreadTaskRunnerManager single_thread_task_runner_manager_; 183 184 std::unique_ptr<ThreadGroup> foreground_thread_group_; 185 std::unique_ptr<ThreadGroup> utility_thread_group_; 186 std::unique_ptr<ThreadGroup> background_thread_group_; 187 188 // Whether this TaskScheduler was started. 189 bool started_ GUARDED_BY_CONTEXT(sequence_checker_) = false; 190 191 // Whether the --disable-best-effort-tasks switch is preventing execution of 192 // BEST_EFFORT tasks until shutdown. 193 const bool has_disable_best_effort_switch_; 194 195 // Number of fences preventing execution of tasks of any/BEST_EFFORT priority. 196 int num_fences_ GUARDED_BY_CONTEXT(sequence_checker_) = 0; 197 int num_best_effort_fences_ GUARDED_BY_CONTEXT(sequence_checker_) = 0; 198 199 #if DCHECK_IS_ON() 200 // Set once JoinForTesting() has returned. 201 AtomicFlag join_for_testing_returned_; 202 #endif 203 204 #if BUILDFLAG(IS_WIN) && defined(COM_INIT_CHECK_HOOK_ENABLED) 205 // Provides COM initialization verification for supported builds. 206 base::win::ComInitCheckHook com_init_check_hook_; 207 #endif 208 209 // Asserts that operations occur in sequence with Start(). 210 SEQUENCE_CHECKER(sequence_checker_); 211 212 TrackedRefFactory<ThreadGroup::Delegate> tracked_ref_factory_; 213 }; 214 215 } // namespace internal 216 } // namespace base 217 218 #endif // BASE_TASK_THREAD_POOL_THREAD_POOL_IMPL_H_ 219