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/*
* Copyright (c) 2017, The Linux Foundation. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* * Neither the name of The Linux Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __SYNC_TASK_H__
#define __SYNC_TASK_H__
#include <thread>
#include <mutex>
#include <condition_variable> // NOLINT
namespace sdm {
template <class TaskCode>
class SyncTask {
public:
// This class need to be overridden by caller to pass on a task context.
class TaskContext {
public:
virtual ~TaskContext() { }
};
// Methods to callback into caller for command codes executions in worker thread.
class TaskHandler {
public:
virtual ~TaskHandler() { }
virtual void OnTask(const TaskCode &task_code, TaskContext *task_context) = 0;
};
explicit SyncTask(TaskHandler &task_handler) : task_handler_(task_handler) {
// Block caller thread until worker thread has started and ready to listen to task commands.
// Worker thread will signal as soon as callback is received in the new thread.
std::unique_lock<std::mutex> caller_lock(caller_mutex_);
std::thread worker_thread(SyncTaskThread, this);
worker_thread_.swap(worker_thread);
caller_cv_.wait(caller_lock);
}
~SyncTask() {
// Task code does not matter here.
PerformTask(task_code_, nullptr, true);
worker_thread_.join();
}
void PerformTask(const TaskCode &task_code, TaskContext *task_context) {
PerformTask(task_code, task_context, false);
}
private:
void PerformTask(const TaskCode &task_code, TaskContext *task_context, bool terminate) {
std::unique_lock<std::mutex> caller_lock(caller_mutex_);
// New scope to limit scope of worker lock to this block.
{
// Set task command code and notify worker thread.
std::unique_lock<std::mutex> worker_lock(worker_mutex_);
task_code_ = task_code;
task_context_ = task_context;
worker_thread_exit_ = terminate;
pending_code_ = true;
worker_cv_.notify_one();
}
// Wait for worker thread to finish and signal.
caller_cv_.wait(caller_lock);
}
static void SyncTaskThread(SyncTask *sync_task) {
if (sync_task) {
sync_task->OnThreadCallback();
}
}
void OnThreadCallback() {
// Acquire worker lock and start waiting for events.
// Wait must start before caller thread can post events, otherwise posted events will be lost.
// Caller thread will be blocked until worker thread signals readiness.
std::unique_lock<std::mutex> worker_lock(worker_mutex_);
// New scope to limit scope of caller lock to this block.
{
// Signal caller thread that worker thread is ready to listen to events.
std::unique_lock<std::mutex> caller_lock(caller_mutex_);
caller_cv_.notify_one();
}
while (!worker_thread_exit_) {
// Add predicate to handle spurious interrupts.
// Wait for caller thread to signal new command codes.
worker_cv_.wait(worker_lock, [this] { return pending_code_; });
// Call task handler which is implemented by the caller.
if (!worker_thread_exit_) {
task_handler_.OnTask(task_code_, task_context_);
}
pending_code_ = false;
// Notify completion of current task to the caller thread which is blocked.
std::unique_lock<std::mutex> caller_lock(caller_mutex_);
caller_cv_.notify_one();
}
}
TaskHandler &task_handler_;
TaskCode task_code_;
TaskContext *task_context_ = nullptr;
std::thread worker_thread_;
std::mutex caller_mutex_;
std::mutex worker_mutex_;
std::condition_variable caller_cv_;
std::condition_variable worker_cv_;
bool worker_thread_exit_ = false;
bool pending_code_ = false;
};
} // namespace sdm
#endif // __SYNC_TASK_H__
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