1/*
2* Copyright (c) 2017, The Linux Foundation. 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 are
6* met:
7*  * Redistributions of source code must retain the above copyright
8*    notice, this list of conditions and the following disclaimer.
9*  * Redistributions in binary form must reproduce the above
10*    copyright notice, this list of conditions and the following
11*    disclaimer in the documentation and/or other materials provided
12*    with the distribution.
13*  * Neither the name of The Linux Foundation nor the names of its
14*    contributors may be used to endorse or promote products derived
15*    from this software without specific prior written permission.
16*
17* THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
18* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
19* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
20* ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
21* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
24* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
25* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
26* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
27* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28*/
29
30#ifndef __SYNC_TASK_H__
31#define __SYNC_TASK_H__
32
33#include <thread>
34#include <mutex>
35#include <condition_variable>   // NOLINT
36
37namespace sdm {
38
39template <class TaskCode>
40class SyncTask {
41 public:
42  // This class need to be overridden by caller to pass on a task context.
43  class TaskContext {
44   public:
45    virtual ~TaskContext() { }
46  };
47
48  // Methods to callback into caller for command codes executions in worker thread.
49  class TaskHandler {
50   public:
51    virtual ~TaskHandler() { }
52    virtual void OnTask(const TaskCode &task_code, TaskContext *task_context) = 0;
53  };
54
55  explicit SyncTask(TaskHandler &task_handler) : task_handler_(task_handler) {
56    // Block caller thread until worker thread has started and ready to listen to task commands.
57    // Worker thread will signal as soon as callback is received in the new thread.
58    std::unique_lock<std::mutex> caller_lock(caller_mutex_);
59    std::thread worker_thread(SyncTaskThread, this);
60    worker_thread_.swap(worker_thread);
61    caller_cv_.wait(caller_lock);
62  }
63
64  ~SyncTask() {
65    // Task code does not matter here.
66    PerformTask(task_code_, nullptr, true);
67    worker_thread_.join();
68  }
69
70  void PerformTask(const TaskCode &task_code, TaskContext *task_context) {
71    PerformTask(task_code, task_context, false);
72  }
73
74 private:
75  void PerformTask(const TaskCode &task_code, TaskContext *task_context, bool terminate) {
76    std::unique_lock<std::mutex> caller_lock(caller_mutex_);
77
78    // New scope to limit scope of worker lock to this block.
79    {
80      // Set task command code and notify worker thread.
81      std::unique_lock<std::mutex> worker_lock(worker_mutex_);
82      task_code_ = task_code;
83      task_context_ = task_context;
84      worker_thread_exit_ = terminate;
85      pending_code_ = true;
86      worker_cv_.notify_one();
87    }
88
89    // Wait for worker thread to finish and signal.
90    caller_cv_.wait(caller_lock);
91  }
92
93  static void SyncTaskThread(SyncTask *sync_task) {
94    if (sync_task) {
95      sync_task->OnThreadCallback();
96    }
97  }
98
99  void OnThreadCallback() {
100    // Acquire worker lock and start waiting for events.
101    // Wait must start before caller thread can post events, otherwise posted events will be lost.
102    // Caller thread will be blocked until worker thread signals readiness.
103    std::unique_lock<std::mutex> worker_lock(worker_mutex_);
104
105    // New scope to limit scope of caller lock to this block.
106    {
107      // Signal caller thread that worker thread is ready to listen to events.
108      std::unique_lock<std::mutex> caller_lock(caller_mutex_);
109      caller_cv_.notify_one();
110    }
111
112    while (!worker_thread_exit_) {
113      // Add predicate to handle spurious interrupts.
114      // Wait for caller thread to signal new command codes.
115      worker_cv_.wait(worker_lock, [this] { return pending_code_; });
116
117      // Call task handler which is implemented by the caller.
118      if (!worker_thread_exit_) {
119        task_handler_.OnTask(task_code_, task_context_);
120      }
121
122      pending_code_ = false;
123      // Notify completion of current task to the caller thread which is blocked.
124      std::unique_lock<std::mutex> caller_lock(caller_mutex_);
125      caller_cv_.notify_one();
126    }
127  }
128
129  TaskHandler &task_handler_;
130  TaskCode task_code_;
131  TaskContext *task_context_ = nullptr;
132  std::thread worker_thread_;
133  std::mutex caller_mutex_;
134  std::mutex worker_mutex_;
135  std::condition_variable caller_cv_;
136  std::condition_variable worker_cv_;
137  bool worker_thread_exit_ = false;
138  bool pending_code_ = false;
139};
140
141}  // namespace sdm
142
143#endif  // __SYNC_TASK_H__
144