uhd/host/lib/utils/tasks.cpp

//
// Copyright 2011,2014 Ettus Research LLC
// Copyright 2018 Ettus Research, a National Instruments Company
//
// SPDX-License-Identifier: GPL-3.0-or-later
//

#include <uhd/exception.hpp>
#include <uhd/utils/log.hpp>
#include <uhd/utils/msg_task.hpp>
#include <uhd/utils/tasks.hpp>
#include <uhd/utils/thread.hpp>
#include <condition_variable>
#include <boost/optional.hpp>
#include <atomic>
#include <exception>
#include <functional>
#include <iostream>
#include <mutex>
#include <thread>
#include <vector>

using namespace uhd;

class task_impl : public task
{
public:
    task_impl(const task_fcn_type& task_fcn, const std::string& name) : _exit(false)
    {
        _task = std::thread([this, task_fcn]() { this->task_loop(task_fcn); });
        if (not name.empty()) {
            set_thread_name(&_task, name);
        }
    }

    ~task_impl(void)
    {
        _exit = true;
        if (_task.joinable()) {
            _task.join();
        }
    }

private:
    void task_loop(const task_fcn_type& task_fcn)
    {
        try {
            while (!_exit) {
                task_fcn();
            }
        } catch (const std::exception& e) {
            do_error_msg(e.what());
        } catch (...) {
            UHD_THROW_INVALID_CODE_PATH();
        }
    }

    void do_error_msg(const std::string& msg)
    {
        UHD_LOGGER_ERROR("UHD")
            << "An unexpected exception was caught in a task loop."
            << "The task loop will now exit, things may not work." << msg;
    }

    std::atomic<bool> _exit;
    std::thread _task;
};

task::sptr task::make(const task_fcn_type& task_fcn, const std::string& name)
{
    return task::sptr(new task_impl(task_fcn, name));
}

msg_task::~msg_task(void)
{
    /* NOP */
}

/*
 * During shutdown pointers to queues for radio_ctrl_core might not be available anymore.
 * msg_task_impl provides a dump_queue for such messages.
 * ctrl_cores can check this queue for stranded messages.
 */

class msg_task_impl : public msg_task
{
public:
    msg_task_impl(const task_fcn_type& task_fcn)
        : _running(false), _thread([this, task_fcn]() { this->task_loop(task_fcn); })
    {
        // Wait for the thread to successfully start
        std::unique_lock<std::mutex> _l(_mutex);

        _start_cv.wait(_l, [this]() { return _running.load(); });
    }

    ~msg_task_impl(void) override
    {
        _running = false;
        if (_thread.joinable()) {
            _thread.join();
        }
    }

    /*
     * Returns the first message for the given SID.
     * This way a radio_ctrl_core doesn't have to die in timeout but can check for
     * stranded messages here. This might happen during shutdown when dtors are called.
     * See also: comments in b200_io_impl->handle_async_task
     */
    msg_payload_t get_msg_from_dump_queue(uint32_t sid) override
    {
        std::lock_guard<std::mutex> lock(_mutex);
        msg_payload_t b;
        for (size_t i = 0; i < _dump_queue.size(); i++) {
            if (sid == _dump_queue[i].first) {
                b = _dump_queue[i].second;
                _dump_queue.erase(_dump_queue.begin() + i);
                break;
            }
        }
        return b;
    }

private:
    void task_loop(const task_fcn_type& task_fcn)
    {
        _running = true;
        _start_cv.notify_one();

        try {
            while (_running) {
                boost::optional<msg_type_t> buff = task_fcn();
                if (buff != boost::none) {
                    /*
                     * If a message gets stranded it is returned by task_fcn and then
                     * pushed to the dump_queue. This way ctrl_cores can check dump_queue
                     * for missing messages.
                     */
                    std::lock_guard<std::mutex> lock(_mutex);
                    _dump_queue.push_back(buff.get());
                }
            }
        } catch (const std::exception& e) {
            do_error_msg(e.what());
        } catch (...) {
            // FIXME
            // Unfortunately, this is also an ok way to end a task,
            // because on some systems boost throws uncatchables.
        }
    }

    void do_error_msg(const std::string& msg)
    {
        UHD_LOGGER_ERROR("UHD")
            << "An unexpected exception was caught in a task loop."
            << "The task loop will now exit, things may not work." << msg;
    }

    std::mutex _mutex;
    std::condition_variable _start_cv;
    std::atomic<bool> _running;
    std::thread _thread;

    /*
     * This queue holds stranded messages until a radio_ctrl_core grabs them via
     * 'get_msg_from_dump_queue'.
     */
    std::vector<msg_type_t> _dump_queue;
};

msg_task::sptr msg_task::make(const task_fcn_type& task_fcn)
{
    return msg_task::sptr(new msg_task_impl(task_fcn));
}