mirror of https://github.com/ArduPilot/ardupilot
AP_HAL_Linux: Add Pollable/Poller
Add system's polling infrastructure to be notified whenever a file descriptor is ready to be read from or written to. Adds a few classes: * Poller, as an interface to epoll() * Pollable, as an interface to a file descriptor
This commit is contained in:
Leandro Pereira
Lucas De Marchi
parent
c859c5ecd9
commit
0f865a019a
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@ -0,0 +1,7 @@
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#pragma once
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#include_next <sys/epoll.h>
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#ifndef EPOLLWAKEUP
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#define EPOLLWAKEUP (1U<<29)
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#endif
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@ -0,0 +1,334 @@
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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/*
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* Copyright (C) 2016 Intel Corporation. All rights reserved.
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*
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* This file is free software: you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This file is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <algorithm>
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#include <cstddef>
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#include <errno.h>
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#include <fcntl.h>
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#include <pthread.h>
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#include <stdint.h>
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#include <sys/epoll.h>
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#include <sys/types.h>
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#include <sys/uio.h>
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#include <unistd.h>
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#include "Poller.h"
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#include "Scheduler.h"
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extern const AP_HAL::HAL& hal;
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namespace Linux {
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uint32_t Poller::to_epoll_events(Poller::Event ev) {
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// EPOLLWAKEUP prevents the system from hibernating or suspending when
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// inside epoll_wait() for this particular event. It is silently
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// ignored if the process does not have the CAP_BLOCK_SUSPEND
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// capability.
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uint32_t op = EPOLLWAKEUP;
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if (ev & Poller::Event::Read) {
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op |= EPOLLIN;
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}
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if (ev & Poller::Event::Write) {
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op |= EPOLLOUT;
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}
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if (ev & Poller::Event::Error) {
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op |= EPOLLERR;
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}
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return op;
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}
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bool Poller::register_pollable(Pollable *p, const Poller::Event ev) {
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if (_epfd < 0) {
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return false;
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}
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struct epoll_event epev = {0};
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epev.events = Poller::to_epoll_events(ev);
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epev.data.ptr = static_cast<void *>(p);
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return epoll_ctl(_epfd, EPOLL_CTL_ADD, p->get_fd(), &epev) == 0;
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}
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void Poller::unregister_pollable(const Pollable *p) {
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if (_epfd >= 0) {
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epoll_ctl(_epfd, EPOLL_CTL_DEL, p->get_fd(), NULL);
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}
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}
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int Poller::poll(int timeout_ms) const {
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const int max_events = 16;
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epoll_event events[max_events];
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const auto before_wait_us = AP_HAL::micros64();
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const auto r = epoll_wait(_epfd, events, max_events, timeout_ms);
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const auto delta_us = AP_HAL::micros64() - before_wait_us;
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const auto delta_ms = delta_us / 1000;
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const auto remaining_time_ms = timeout_ms - delta_ms;
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if (r > 0) {
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auto max_time_ms = remaining_time_ms / r;
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if (!max_time_ms) {
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max_time_ms = 1;
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}
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for (int i = 0; i < r; i++) {
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Pollable *p = static_cast<Pollable *>(events[i].data.ptr);
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if (events[i].events & EPOLLIN) {
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p->on_can_read(max_time_ms);
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}
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if (events[i].events & EPOLLOUT) {
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p->on_can_write(max_time_ms);
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}
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if (events[i].events & EPOLLERR) {
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p->on_error(max_time_ms);
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}
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if (events[i].events & EPOLLHUP) {
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p->on_hang_up(max_time_ms);
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}
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}
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} else if (r < 0) {
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if (errno == EINTR) {
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// Try polling again with the remaining wait time.
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return poll(remaining_time_ms);
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}
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}
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return r;
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}
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Pollable::~Pollable() {
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close(_fd);
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}
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bool Pollable::set_blocking(bool setting) {
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auto curflags = fcntl(_fd, F_GETFL, 0);
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if (curflags < 0) {
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return false;
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}
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if (setting) {
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curflags &= ~O_NONBLOCK;
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} else {
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curflags |= O_NONBLOCK;
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}
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return fcntl(_fd, F_SETFL, curflags) == 0;
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}
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void BufferedPollable::on_can_read(int max_time_ms) {
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if (!_read_sem.take(max_time_ms)) {
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return;
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}
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ByteBuffer::IoVec vec[2];
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const auto n_vec = _read_buffer.reserve(vec, _read_buffer.space());
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if (n_vec) {
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struct iovec iovec[n_vec];
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for (int i = 0; i < n_vec; i++) {
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iovec[i].iov_base = static_cast<void *>(vec[i].data);
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iovec[i].iov_len = static_cast<size_t>(vec[i].len);
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}
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(void) readv(_fd, iovec, n_vec);
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}
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_read_sem.give();
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}
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void BufferedPollable::on_hang_up(int max_time_ms) {
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auto half_time_ms = max_time_ms / 2;
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if (!_read_sem.take(half_time_ms)) {
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return;
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}
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if (_write_sem.take(half_time_ms)) {
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_read_buffer.advance(_read_buffer.available());
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_write_buffer.advance(_write_buffer.available());
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close(_fd);
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_fd = -1;
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_write_sem.give();
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}
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_read_sem.give();
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}
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void BufferedPollable::write_fd(uint32_t n_bytes) {
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// NOTE: Must be called with _write_sem taken.
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if (!n_bytes) {
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return;
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}
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ByteBuffer::IoVec vec[2];
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auto n_vec = _write_buffer.peekiovec(vec, n_bytes);
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if (!n_vec) {
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return;
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}
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struct iovec iovec[n_vec];
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for (int i = 0; i < n_vec; i++) {
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iovec[i].iov_base = static_cast<void *>(vec[i].data);
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iovec[i].iov_len = static_cast<size_t>(vec[i].len);
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}
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auto written = writev(_fd, iovec, n_vec);
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if (written > 0) {
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_write_buffer.advance(static_cast<uint32_t>(written));
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}
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}
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void BufferedPollable::on_can_write(int max_time_ms) {
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if (_write_sem.take(max_time_ms)) {
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write_fd(_write_buffer.available());
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_write_sem.give();
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}
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}
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bool BufferedPollable::is_write_buffer_empty() {
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bool ret = false;
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if (_write_sem.take_nonblocking()) {
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ret = _write_buffer.available() > 0;
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_write_sem.give();
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}
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return ret;
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}
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uint32_t BufferedPollable::get_read_buffer_available() {
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uint32_t ret = 0;
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if (_read_sem.take_nonblocking()) {
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ret = _read_buffer.available();
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_read_sem.give();
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}
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return ret;
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}
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uint32_t BufferedPollable::get_write_buffer_available() {
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uint32_t ret = 0;
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if (_write_sem.take_nonblocking()) {
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ret = _write_buffer.available();
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_write_sem.give();
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}
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return ret;
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}
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uint32_t BufferedPollable::buffered_read(uint8_t *ptr, uint32_t len) {
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uint32_t ret = 0;
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bool taken_sem;
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if (_blocking_reads) {
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taken_sem = _read_sem.take(100);
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} else {
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taken_sem = _read_sem.take_nonblocking();
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}
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if (taken_sem) {
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ret = _read_buffer.read(ptr, len);
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_read_sem.give();
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}
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return ret;
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}
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uint32_t BufferedPollable::buffered_write(const uint8_t *buf, uint32_t len) {
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uint32_t ret = 0;
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bool taken_sem;
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if (_blocking_writes) {
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taken_sem = _write_sem.take(100);
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} else {
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taken_sem = _write_sem.take_nonblocking();
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}
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if (taken_sem) {
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if (_write_buffer.space() >= len) {
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ret = _write_buffer.write(buf, len);
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}
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_write_sem.give();
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}
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return ret;
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}
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uint32_t PacketedBufferedPollable::to_mavlink_boundary(uint32_t available) {
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// NOTE: Must be called with _write_sem taken.
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const uint32_t mavlink_hdr_size = 8; // 6-byte header + 2-byte cksum.
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const uint32_t mavlink_max_size = 256;
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const uint8_t mavlink_marker = 254;
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if (!available) {
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return 0;
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}
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if (_write_buffer.peek(0) != mavlink_marker) {
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// Non-mavlink packet at the start of the buffer. Look ahead for a
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// MAVLink start byte, up to 256 bytes ahead.
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const auto limit = std::min(mavlink_max_size, available);
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uint32_t contiguous_avail;
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const uint8_t *ptr = _write_buffer.readptr(contiguous_avail);
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if (contiguous_avail >= limit) {
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// If there's enough contiguous data in the ring buffer, use a
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// fast byte scan instead. This should happen more often.
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auto marker_pos = memchr(ptr, mavlink_marker, limit);
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if (marker_pos) {
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return static_cast<uint32_t>(
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static_cast<const uint8_t *>(marker_pos) - ptr);
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}
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} else {
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for (uint32_t i = 0; i < limit; i++) {
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if (_write_buffer.peek(i) == mavlink_marker) {
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return i;
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}
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}
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}
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// No MAVLink marker, limit the send size to mavlink_max_size.
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return limit;
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}
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if (available < mavlink_hdr_size) {
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return 0; // Not a full MAVLink packet yet.
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}
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// Possible MAVLink packet, just check if it is complete.
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const auto pktlen = _write_buffer.peek(1); // Length is on 2nd byte.
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if (pktlen == -1 || available < static_cast<uint8_t>(pktlen) + mavlink_hdr_size) {
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return 0; // Not a full MAVLink packet yet.
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}
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// Packet seems complete. Send one at a time.
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return pktlen + mavlink_hdr_size;
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}
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void PacketedBufferedPollable::on_can_write(int max_time_ms) {
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if (_write_sem.take(max_time_ms)) {
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write_fd(to_mavlink_boundary(_write_buffer.available()));
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_write_sem.give();
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}
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}
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}
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@ -0,0 +1,111 @@
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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/*
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* Copyright (C) 2016 Intel Corporation. All rights reserved.
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*
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* This file is free software: you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This file is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <sys/epoll.h>
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#include <unistd.h>
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#include "AP_HAL/utility/RingBuffer.h"
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#include "Semaphores.h"
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namespace Linux {
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class Pollable {
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public:
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Pollable(int fd) : _fd(fd) { }
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virtual ~Pollable();
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int get_fd() const { return _fd; }
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bool set_blocking(bool setting);
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virtual void on_can_read(int max_time_ms) {}
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virtual void on_can_write(int max_time_ms) {}
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virtual void on_error(int max_time_ms) {}
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virtual void on_hang_up(int max_time_ms) {}
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protected:
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int _fd;
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};
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class BufferedPollable : public Pollable {
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public:
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BufferedPollable(int fd) : Pollable(fd) { }
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BufferedPollable(int fd, uint32_t read_buffer_size, uint32_t write_buffer_size)
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: Pollable(fd)
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, _read_buffer{read_buffer_size}
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, _write_buffer{write_buffer_size} { }
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bool is_write_buffer_empty();
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uint32_t get_read_buffer_available();
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uint32_t get_write_buffer_available();
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uint32_t buffered_read(uint8_t *buf, uint32_t len);
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uint32_t buffered_write(const uint8_t *buf, uint32_t len);
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void set_blocking_writes(bool setting) { _blocking_writes = setting; }
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void set_blocking_reads(bool setting) { _blocking_reads = setting; }
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virtual void on_can_read(int max_time_ms) override;
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virtual void on_can_write(int max_time_ms) override;
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virtual void on_hang_up(int max_time_ms) override;
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protected:
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ByteBuffer _read_buffer{1024}, _write_buffer{1024};
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Linux::Semaphore _write_sem, _read_sem;
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void write_fd(uint32_t n_bytes);
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private:
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bool _blocking_writes{false}, _blocking_reads{false};
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};
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class PacketedBufferedPollable : public BufferedPollable {
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private:
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uint32_t to_mavlink_boundary(uint32_t available);
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public:
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PacketedBufferedPollable(int fd) : BufferedPollable(fd) { }
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virtual void on_can_write(int max_time_ms) override;
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};
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class Poller {
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public:
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Poller() : _epfd(epoll_create1(EPOLL_CLOEXEC)) { }
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~Poller() { close(_epfd); }
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enum Event : uint8_t {
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Read = 1<<0,
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Write = 1<<1,
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Error = 1<<2,
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All = Read | Write | Error
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};
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bool register_pollable(Pollable*, const Event);
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void unregister_pollable(const Pollable*);
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int poll(int timeout_ms) const;
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private:
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int _epfd;
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static uint32_t to_epoll_events(Event events);
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};
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}
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