1*6777b538SAndroid Build Coastguard Worker // Copyright 2014 The Chromium Authors 2*6777b538SAndroid Build Coastguard Worker // Use of this source code is governed by a BSD-style license that can be 3*6777b538SAndroid Build Coastguard Worker // found in the LICENSE file. 4*6777b538SAndroid Build Coastguard Worker 5*6777b538SAndroid Build Coastguard Worker // CancelableTaskTracker posts tasks (in the form of a OnceClosure) to a 6*6777b538SAndroid Build Coastguard Worker // TaskRunner, and is able to cancel the task later if it's not needed 7*6777b538SAndroid Build Coastguard Worker // anymore. On destruction, CancelableTaskTracker will cancel all 8*6777b538SAndroid Build Coastguard Worker // tracked tasks. 9*6777b538SAndroid Build Coastguard Worker // 10*6777b538SAndroid Build Coastguard Worker // Each cancelable task can be associated with a reply (also a OnceClosure). 11*6777b538SAndroid Build Coastguard Worker // After the task is run on the TaskRunner, |reply| will be posted back to 12*6777b538SAndroid Build Coastguard Worker // originating TaskRunner. 13*6777b538SAndroid Build Coastguard Worker // 14*6777b538SAndroid Build Coastguard Worker // NOTE: 15*6777b538SAndroid Build Coastguard Worker // 16*6777b538SAndroid Build Coastguard Worker // CancelableOnceCallback (base/cancelable_callback.h) and WeakPtr binding are 17*6777b538SAndroid Build Coastguard Worker // preferred solutions for canceling a task. However, they don't support 18*6777b538SAndroid Build Coastguard Worker // cancelation from another sequence. This is sometimes a performance critical 19*6777b538SAndroid Build Coastguard Worker // requirement. E.g. We need to cancel database lookup task on DB thread when 20*6777b538SAndroid Build Coastguard Worker // user changes inputted text. If it is performance critical to do a best effort 21*6777b538SAndroid Build Coastguard Worker // cancelation of a task, then CancelableTaskTracker is appropriate, otherwise 22*6777b538SAndroid Build Coastguard Worker // use one of the other mechanisms. 23*6777b538SAndroid Build Coastguard Worker // 24*6777b538SAndroid Build Coastguard Worker // THREAD-SAFETY: 25*6777b538SAndroid Build Coastguard Worker // 26*6777b538SAndroid Build Coastguard Worker // 1. A CancelableTaskTracker object must be created, used, and destroyed on a 27*6777b538SAndroid Build Coastguard Worker // single sequence. 28*6777b538SAndroid Build Coastguard Worker // 29*6777b538SAndroid Build Coastguard Worker // 2. It's safe to destroy a CancelableTaskTracker while there are outstanding 30*6777b538SAndroid Build Coastguard Worker // tasks. This is commonly used to cancel all outstanding tasks. 31*6777b538SAndroid Build Coastguard Worker // 32*6777b538SAndroid Build Coastguard Worker // 3. The task is deleted on the target sequence, and the reply are deleted on 33*6777b538SAndroid Build Coastguard Worker // the originating sequence. 34*6777b538SAndroid Build Coastguard Worker // 35*6777b538SAndroid Build Coastguard Worker // 4. IsCanceledCallback can be run or deleted on any sequence. 36*6777b538SAndroid Build Coastguard Worker #ifndef BASE_TASK_CANCELABLE_TASK_TRACKER_H_ 37*6777b538SAndroid Build Coastguard Worker #define BASE_TASK_CANCELABLE_TASK_TRACKER_H_ 38*6777b538SAndroid Build Coastguard Worker 39*6777b538SAndroid Build Coastguard Worker #include <stdint.h> 40*6777b538SAndroid Build Coastguard Worker 41*6777b538SAndroid Build Coastguard Worker #include <memory> 42*6777b538SAndroid Build Coastguard Worker #include <utility> 43*6777b538SAndroid Build Coastguard Worker 44*6777b538SAndroid Build Coastguard Worker #include "base/base_export.h" 45*6777b538SAndroid Build Coastguard Worker #include "base/containers/small_map.h" 46*6777b538SAndroid Build Coastguard Worker #include "base/functional/bind.h" 47*6777b538SAndroid Build Coastguard Worker #include "base/functional/callback.h" 48*6777b538SAndroid Build Coastguard Worker #include "base/functional/callback_helpers.h" 49*6777b538SAndroid Build Coastguard Worker #include "base/memory/ref_counted.h" 50*6777b538SAndroid Build Coastguard Worker #include "base/memory/weak_ptr.h" 51*6777b538SAndroid Build Coastguard Worker #include "base/sequence_checker.h" 52*6777b538SAndroid Build Coastguard Worker #include "base/synchronization/atomic_flag.h" 53*6777b538SAndroid Build Coastguard Worker #include "base/task/post_task_and_reply_with_result_internal.h" 54*6777b538SAndroid Build Coastguard Worker 55*6777b538SAndroid Build Coastguard Worker namespace base { 56*6777b538SAndroid Build Coastguard Worker 57*6777b538SAndroid Build Coastguard Worker class Location; 58*6777b538SAndroid Build Coastguard Worker class ScopedClosureRunner; 59*6777b538SAndroid Build Coastguard Worker class TaskRunner; 60*6777b538SAndroid Build Coastguard Worker 61*6777b538SAndroid Build Coastguard Worker class BASE_EXPORT CancelableTaskTracker { 62*6777b538SAndroid Build Coastguard Worker public: 63*6777b538SAndroid Build Coastguard Worker // All values except kBadTaskId are valid. 64*6777b538SAndroid Build Coastguard Worker typedef int64_t TaskId; 65*6777b538SAndroid Build Coastguard Worker static const TaskId kBadTaskId; 66*6777b538SAndroid Build Coastguard Worker 67*6777b538SAndroid Build Coastguard Worker using IsCanceledCallback = RepeatingCallback<bool()>; 68*6777b538SAndroid Build Coastguard Worker 69*6777b538SAndroid Build Coastguard Worker CancelableTaskTracker(); 70*6777b538SAndroid Build Coastguard Worker 71*6777b538SAndroid Build Coastguard Worker CancelableTaskTracker(const CancelableTaskTracker&) = delete; 72*6777b538SAndroid Build Coastguard Worker CancelableTaskTracker& operator=(const CancelableTaskTracker&) = delete; 73*6777b538SAndroid Build Coastguard Worker 74*6777b538SAndroid Build Coastguard Worker // Cancels all tracked tasks. 75*6777b538SAndroid Build Coastguard Worker ~CancelableTaskTracker(); 76*6777b538SAndroid Build Coastguard Worker 77*6777b538SAndroid Build Coastguard Worker TaskId PostTask(TaskRunner* task_runner, 78*6777b538SAndroid Build Coastguard Worker const Location& from_here, 79*6777b538SAndroid Build Coastguard Worker OnceClosure task); 80*6777b538SAndroid Build Coastguard Worker 81*6777b538SAndroid Build Coastguard Worker TaskId PostTaskAndReply(TaskRunner* task_runner, 82*6777b538SAndroid Build Coastguard Worker const Location& from_here, 83*6777b538SAndroid Build Coastguard Worker OnceClosure task, 84*6777b538SAndroid Build Coastguard Worker OnceClosure reply); 85*6777b538SAndroid Build Coastguard Worker 86*6777b538SAndroid Build Coastguard Worker template <typename TaskReturnType, typename ReplyArgType> PostTaskAndReplyWithResult(TaskRunner * task_runner,const Location & from_here,OnceCallback<TaskReturnType ()> task,OnceCallback<void (ReplyArgType)> reply)87*6777b538SAndroid Build Coastguard Worker TaskId PostTaskAndReplyWithResult(TaskRunner* task_runner, 88*6777b538SAndroid Build Coastguard Worker const Location& from_here, 89*6777b538SAndroid Build Coastguard Worker OnceCallback<TaskReturnType()> task, 90*6777b538SAndroid Build Coastguard Worker OnceCallback<void(ReplyArgType)> reply) { 91*6777b538SAndroid Build Coastguard Worker auto* result = new std::unique_ptr<TaskReturnType>(); 92*6777b538SAndroid Build Coastguard Worker return PostTaskAndReply( 93*6777b538SAndroid Build Coastguard Worker task_runner, from_here, 94*6777b538SAndroid Build Coastguard Worker BindOnce(&internal::ReturnAsParamAdapter<TaskReturnType>, 95*6777b538SAndroid Build Coastguard Worker std::move(task), Unretained(result)), 96*6777b538SAndroid Build Coastguard Worker BindOnce(&internal::ReplyAdapter<TaskReturnType, ReplyArgType>, 97*6777b538SAndroid Build Coastguard Worker std::move(reply), Owned(result))); 98*6777b538SAndroid Build Coastguard Worker } 99*6777b538SAndroid Build Coastguard Worker 100*6777b538SAndroid Build Coastguard Worker // Creates a tracked TaskId and an associated IsCanceledCallback. Client can 101*6777b538SAndroid Build Coastguard Worker // later call TryCancel() with the returned TaskId, and run |is_canceled_cb| 102*6777b538SAndroid Build Coastguard Worker // from any thread to check whether the TaskId is canceled. 103*6777b538SAndroid Build Coastguard Worker // 104*6777b538SAndroid Build Coastguard Worker // The returned task ID is tracked until the last copy of 105*6777b538SAndroid Build Coastguard Worker // |is_canceled_cb| is destroyed. 106*6777b538SAndroid Build Coastguard Worker // 107*6777b538SAndroid Build Coastguard Worker // Note. This function is used to address some special cancelation requirement 108*6777b538SAndroid Build Coastguard Worker // in existing code. You SHOULD NOT need this function in new code. 109*6777b538SAndroid Build Coastguard Worker TaskId NewTrackedTaskId(IsCanceledCallback* is_canceled_cb); 110*6777b538SAndroid Build Coastguard Worker 111*6777b538SAndroid Build Coastguard Worker // After calling this function, |task| and |reply| will not run. If the 112*6777b538SAndroid Build Coastguard Worker // cancelation happens when |task| is running or has finished running, |reply| 113*6777b538SAndroid Build Coastguard Worker // will not run. If |reply| is running or has finished running, cancellation 114*6777b538SAndroid Build Coastguard Worker // is a noop. 115*6777b538SAndroid Build Coastguard Worker // 116*6777b538SAndroid Build Coastguard Worker // Note. It's OK to cancel a |task| for more than once. The later calls are 117*6777b538SAndroid Build Coastguard Worker // noops. 118*6777b538SAndroid Build Coastguard Worker void TryCancel(TaskId id); 119*6777b538SAndroid Build Coastguard Worker 120*6777b538SAndroid Build Coastguard Worker // It's OK to call this function for more than once. The later calls are 121*6777b538SAndroid Build Coastguard Worker // noops. 122*6777b538SAndroid Build Coastguard Worker void TryCancelAll(); 123*6777b538SAndroid Build Coastguard Worker 124*6777b538SAndroid Build Coastguard Worker // Returns true iff there are in-flight tasks that are still being 125*6777b538SAndroid Build Coastguard Worker // tracked. 126*6777b538SAndroid Build Coastguard Worker bool HasTrackedTasks() const; 127*6777b538SAndroid Build Coastguard Worker 128*6777b538SAndroid Build Coastguard Worker private: 129*6777b538SAndroid Build Coastguard Worker // Cancellation flags are ref-counted to ensure they remain valid even if the 130*6777b538SAndroid Build Coastguard Worker // tracker and its calling thread are torn down while there are still 131*6777b538SAndroid Build Coastguard Worker // cancelable tasks queued to the target TaskRunner. 132*6777b538SAndroid Build Coastguard Worker // See https://crbug.com/918948. 133*6777b538SAndroid Build Coastguard Worker using TaskCancellationFlag = RefCountedData<AtomicFlag>; 134*6777b538SAndroid Build Coastguard Worker 135*6777b538SAndroid Build Coastguard Worker static void RunIfNotCanceled(const scoped_refptr<TaskCancellationFlag>& flag, 136*6777b538SAndroid Build Coastguard Worker OnceClosure task); 137*6777b538SAndroid Build Coastguard Worker static void RunThenUntrackIfNotCanceled( 138*6777b538SAndroid Build Coastguard Worker const scoped_refptr<TaskCancellationFlag>& flag, 139*6777b538SAndroid Build Coastguard Worker OnceClosure task, 140*6777b538SAndroid Build Coastguard Worker OnceClosure untrack); 141*6777b538SAndroid Build Coastguard Worker static bool IsCanceled(const scoped_refptr<TaskCancellationFlag>& flag, 142*6777b538SAndroid Build Coastguard Worker const ScopedClosureRunner& cleanup_runner); 143*6777b538SAndroid Build Coastguard Worker 144*6777b538SAndroid Build Coastguard Worker void Track(TaskId id, scoped_refptr<TaskCancellationFlag> flag); 145*6777b538SAndroid Build Coastguard Worker void Untrack(TaskId id); 146*6777b538SAndroid Build Coastguard Worker 147*6777b538SAndroid Build Coastguard Worker // Typically the number of tasks are 0-2 and occationally 3-4. But since 148*6777b538SAndroid Build Coastguard Worker // this is a general API that could be used in unexpected ways, use a 149*6777b538SAndroid Build Coastguard Worker // small_map instead of a flat_map to avoid falling over if there are many 150*6777b538SAndroid Build Coastguard Worker // tasks. 151*6777b538SAndroid Build Coastguard Worker small_map<std::map<TaskId, scoped_refptr<TaskCancellationFlag>>, 4> 152*6777b538SAndroid Build Coastguard Worker task_flags_; 153*6777b538SAndroid Build Coastguard Worker 154*6777b538SAndroid Build Coastguard Worker TaskId next_id_ = 1; 155*6777b538SAndroid Build Coastguard Worker SEQUENCE_CHECKER(sequence_checker_); 156*6777b538SAndroid Build Coastguard Worker 157*6777b538SAndroid Build Coastguard Worker // TODO(https://crbug.com/1009795): Remove once crasher is resolved. 158*6777b538SAndroid Build Coastguard Worker base::WeakPtr<CancelableTaskTracker> weak_this_; 159*6777b538SAndroid Build Coastguard Worker base::WeakPtrFactory<CancelableTaskTracker> weak_factory_{this}; 160*6777b538SAndroid Build Coastguard Worker }; 161*6777b538SAndroid Build Coastguard Worker 162*6777b538SAndroid Build Coastguard Worker } // namespace base 163*6777b538SAndroid Build Coastguard Worker 164*6777b538SAndroid Build Coastguard Worker #endif // BASE_TASK_CANCELABLE_TASK_TRACKER_H_ 165