1 // Copyright 2013 The Chromium 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 BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_ 6 #define BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_ 7 8 #include "base/base_export.h" 9 #include "base/memory/ref_counted.h" 10 #include "base/pending_task.h" 11 #include "base/synchronization/lock.h" 12 #include "base/time/time.h" 13 14 namespace base { 15 16 class MessageLoop; 17 class WaitableEvent; 18 19 namespace internal { 20 21 // Implements a queue of tasks posted to the message loop running on the current 22 // thread. This class takes care of synchronizing posting tasks from different 23 // threads and together with MessageLoop ensures clean shutdown. 24 class BASE_EXPORT IncomingTaskQueue 25 : public RefCountedThreadSafe<IncomingTaskQueue> { 26 public: 27 explicit IncomingTaskQueue(MessageLoop* message_loop); 28 29 // Appends a task to the incoming queue. Posting of all tasks is routed though 30 // AddToIncomingQueue() or TryAddToIncomingQueue() to make sure that posting 31 // task is properly synchronized between different threads. 32 // 33 // Returns true if the task was successfully added to the queue, otherwise 34 // returns false. In all cases, the ownership of |task| is transferred to the 35 // called method. 36 bool AddToIncomingQueue(const tracked_objects::Location& from_here, 37 const Closure& task, 38 TimeDelta delay, 39 bool nestable); 40 41 // Returns true if the queue contains tasks that require higher than default 42 // timer resolution. Currently only needed for Windows. 43 bool HasHighResolutionTasks(); 44 45 // Returns true if the message loop is "idle". Provided for testing. 46 bool IsIdleForTesting(); 47 48 // Loads tasks from the |incoming_queue_| into |*work_queue|. Must be called 49 // from the thread that is running the loop. Returns the number of tasks that 50 // require high resolution timers. 51 int ReloadWorkQueue(TaskQueue* work_queue); 52 53 // Disconnects |this| from the parent message loop. 54 void WillDestroyCurrentMessageLoop(); 55 56 private: 57 friend class RefCountedThreadSafe<IncomingTaskQueue>; 58 virtual ~IncomingTaskQueue(); 59 60 // Calculates the time at which a PendingTask should run. 61 TimeTicks CalculateDelayedRuntime(TimeDelta delay); 62 63 // Adds a task to |incoming_queue_|. The caller retains ownership of 64 // |pending_task|, but this function will reset the value of 65 // |pending_task->task|. This is needed to ensure that the posting call stack 66 // does not retain |pending_task->task| beyond this function call. 67 bool PostPendingTask(PendingTask* pending_task); 68 69 // Number of tasks that require high resolution timing. This value is kept 70 // so that ReloadWorkQueue() completes in constant time. 71 int high_res_task_count_; 72 73 // The lock that protects access to the members of this class. 74 base::Lock incoming_queue_lock_; 75 76 // An incoming queue of tasks that are acquired under a mutex for processing 77 // on this instance's thread. These tasks have not yet been been pushed to 78 // |message_loop_|. 79 TaskQueue incoming_queue_; 80 81 // Points to the message loop that owns |this|. 82 MessageLoop* message_loop_; 83 84 // The next sequence number to use for delayed tasks. 85 int next_sequence_num_; 86 87 DISALLOW_COPY_AND_ASSIGN(IncomingTaskQueue); 88 }; 89 90 } // namespace internal 91 } // namespace base 92 93 #endif // BASE_MESSAGE_LOOP_INCOMING_TASK_QUEUE_H_ 94