native: Remove timerfd implementation on linux
Rust advertises itself as being compatible with linux 2.6.18, but the timerfd set of syscalls weren't added until linux 2.6.25. There is no real need for a specialized timer implementation beyond being a "little more accurate", but the select() implementation will suffice for now. If it is later deemed that an accurate timerfd implementation is needed, it can be added then through some method which will allow the standard distribution to continue to be compatible with 2.6.18 Closes #13447
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Alex Crichton
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3 changed files with 6 additions and 333 deletions
341
src/libnative/io/timer_unix.rs
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341
src/libnative/io/timer_unix.rs
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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Timers for non-linux/non-windows OSes
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//!
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//! This module implements timers with a worker thread, select(), and a lot of
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//! witchcraft that turns out to be horribly inaccurate timers. The unfortunate
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//! part is that I'm at a loss of what else to do one these OSes. This is also
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//! why linux has a specialized timerfd implementation and windows has its own
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//! implementation (they're more accurate than this one).
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//!
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//! The basic idea is that there is a worker thread that's communicated to via a
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//! channel and a pipe, the pipe is used by the worker thread in a select()
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//! syscall with a timeout. The timeout is the "next timer timeout" while the
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//! channel is used to send data over to the worker thread.
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//!
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//! Whenever the call to select() times out, then a channel receives a message.
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//! Whenever the call returns that the file descriptor has information, then the
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//! channel from timers is drained, enqueueing all incoming requests.
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//!
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//! The actual implementation of the helper thread is a sorted array of
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//! timers in terms of target firing date. The target is the absolute time at
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//! which the timer should fire. Timers are then re-enqueued after a firing if
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//! the repeat boolean is set.
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//!
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//! Naturally, all this logic of adding times and keeping track of
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//! relative/absolute time is a little lossy and not quite exact. I've done the
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//! best I could to reduce the amount of calls to 'now()', but there's likely
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//! still inaccuracies trickling in here and there.
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//!
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//! One of the tricky parts of this implementation is that whenever a timer is
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//! acted upon, it must cancel whatever the previous action was (if one is
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//! active) in order to act like the other implementations of this timer. In
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//! order to do this, the timer's inner pointer is transferred to the worker
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//! thread. Whenever the timer is modified, it first takes ownership back from
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//! the worker thread in order to modify the same data structure. This has the
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//! side effect of "cancelling" the previous requests while allowing a
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//! re-enqueueing later on.
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//!
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//! Note that all time units in this file are in *milliseconds*.
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use libc;
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use std::mem;
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use std::os;
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use std::ptr;
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use std::rt::rtio;
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use std::sync::atomics;
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use io::file::FileDesc;
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use io::IoResult;
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use io::timer_helper;
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pub struct Timer {
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id: uint,
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inner: Option<~Inner>,
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}
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struct Inner {
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tx: Option<Sender<()>>,
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interval: u64,
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repeat: bool,
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target: u64,
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id: uint,
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}
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#[allow(visible_private_types)]
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pub enum Req {
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// Add a new timer to the helper thread.
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NewTimer(~Inner),
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// Remove a timer based on its id and then send it back on the channel
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// provided
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RemoveTimer(uint, Sender<~Inner>),
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// Shut down the loop and then ACK this channel once it's shut down
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Shutdown,
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}
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// returns the current time (in milliseconds)
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fn now() -> u64 {
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unsafe {
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let mut now: libc::timeval = mem::init();
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assert_eq!(imp::gettimeofday(&mut now, ptr::null()), 0);
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return (now.tv_sec as u64) * 1000 + (now.tv_usec as u64) / 1000;
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}
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}
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fn helper(input: libc::c_int, messages: Receiver<Req>) {
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let mut set: imp::fd_set = unsafe { mem::init() };
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let mut fd = FileDesc::new(input, true);
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let mut timeout: libc::timeval = unsafe { mem::init() };
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// active timers are those which are able to be selected upon (and it's a
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// sorted list, and dead timers are those which have expired, but ownership
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// hasn't yet been transferred back to the timer itself.
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let mut active: Vec<~Inner> = vec![];
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let mut dead = vec![];
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// inserts a timer into an array of timers (sorted by firing time)
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fn insert(t: ~Inner, active: &mut Vec<~Inner>) {
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match active.iter().position(|tm| tm.target > t.target) {
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Some(pos) => { active.insert(pos, t); }
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None => { active.push(t); }
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}
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}
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// signals the first requests in the queue, possible re-enqueueing it.
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fn signal(active: &mut Vec<~Inner>, dead: &mut Vec<(uint, ~Inner)>) {
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let mut timer = match active.shift() {
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Some(timer) => timer, None => return
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};
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let tx = timer.tx.take_unwrap();
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if tx.send_opt(()).is_ok() && timer.repeat {
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timer.tx = Some(tx);
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timer.target += timer.interval;
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insert(timer, active);
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} else {
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drop(tx);
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dead.push((timer.id, timer));
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}
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}
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'outer: loop {
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let timeout = if active.len() == 0 {
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// Empty array? no timeout (wait forever for the next request)
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ptr::null()
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} else {
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let now = now();
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// If this request has already expired, then signal it and go
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// through another iteration
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if active.get(0).target <= now {
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signal(&mut active, &mut dead);
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continue;
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}
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// The actual timeout listed in the requests array is an
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// absolute date, so here we translate the absolute time to a
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// relative time.
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let tm = active.get(0).target - now;
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timeout.tv_sec = (tm / 1000) as libc::time_t;
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timeout.tv_usec = ((tm % 1000) * 1000) as libc::suseconds_t;
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&timeout as *libc::timeval
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};
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imp::fd_set(&mut set, input);
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match unsafe {
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imp::select(input + 1, &set, ptr::null(), ptr::null(), timeout)
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} {
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// timed out
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0 => signal(&mut active, &mut dead),
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// file descriptor write woke us up, we've got some new requests
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1 => {
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loop {
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match messages.try_recv() {
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Ok(Shutdown) => {
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assert!(active.len() == 0);
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break 'outer;
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}
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Ok(NewTimer(timer)) => insert(timer, &mut active),
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Ok(RemoveTimer(id, ack)) => {
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match dead.iter().position(|&(i, _)| id == i) {
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Some(i) => {
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let (_, i) = dead.remove(i).unwrap();
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ack.send(i);
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continue
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}
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None => {}
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}
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let i = active.iter().position(|i| i.id == id);
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let i = i.expect("no timer found");
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let t = active.remove(i).unwrap();
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ack.send(t);
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}
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_ => break
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}
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}
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// drain the file descriptor
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let mut buf = [0];
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assert_eq!(fd.inner_read(buf).unwrap(), 1);
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}
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-1 if os::errno() == libc::EINTR as int => {}
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n => fail!("helper thread failed in select() with error: {} ({})",
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n, os::last_os_error())
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}
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}
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}
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impl Timer {
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pub fn new() -> IoResult<Timer> {
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timer_helper::boot(helper);
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static mut ID: atomics::AtomicUint = atomics::INIT_ATOMIC_UINT;
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let id = unsafe { ID.fetch_add(1, atomics::Relaxed) };
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Ok(Timer {
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id: id,
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inner: Some(~Inner {
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tx: None,
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interval: 0,
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target: 0,
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repeat: false,
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id: id,
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})
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})
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}
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pub fn sleep(ms: u64) {
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let mut to_sleep = libc::timespec {
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tv_sec: (ms / 1000) as libc::time_t,
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tv_nsec: ((ms % 1000) * 1000000) as libc::c_long,
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};
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while unsafe { libc::nanosleep(&to_sleep, &mut to_sleep) } != 0 {
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if os::errno() as int != libc::EINTR as int {
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fail!("failed to sleep, but not because of EINTR?");
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}
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}
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}
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fn inner(&mut self) -> ~Inner {
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match self.inner.take() {
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Some(i) => i,
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None => {
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let (tx, rx) = channel();
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timer_helper::send(RemoveTimer(self.id, tx));
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rx.recv()
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}
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}
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}
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}
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impl rtio::RtioTimer for Timer {
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fn sleep(&mut self, msecs: u64) {
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let mut inner = self.inner();
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inner.tx = None; // cancel any previous request
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self.inner = Some(inner);
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Timer::sleep(msecs);
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}
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fn oneshot(&mut self, msecs: u64) -> Receiver<()> {
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let now = now();
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let mut inner = self.inner();
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let (tx, rx) = channel();
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inner.repeat = false;
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inner.tx = Some(tx);
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inner.interval = msecs;
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inner.target = now + msecs;
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timer_helper::send(NewTimer(inner));
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return rx;
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}
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fn period(&mut self, msecs: u64) -> Receiver<()> {
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let now = now();
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let mut inner = self.inner();
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let (tx, rx) = channel();
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inner.repeat = true;
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inner.tx = Some(tx);
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inner.interval = msecs;
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inner.target = now + msecs;
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timer_helper::send(NewTimer(inner));
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return rx;
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}
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}
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impl Drop for Timer {
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fn drop(&mut self) {
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self.inner = Some(self.inner());
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}
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}
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#[cfg(target_os = "macos")]
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mod imp {
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use libc;
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pub static FD_SETSIZE: uint = 1024;
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pub struct fd_set {
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fds_bits: [i32, ..(FD_SETSIZE / 32)]
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}
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pub fn fd_set(set: &mut fd_set, fd: i32) {
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set.fds_bits[(fd / 32) as uint] |= 1 << (fd % 32);
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}
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extern {
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pub fn select(nfds: libc::c_int,
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readfds: *fd_set,
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writefds: *fd_set,
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errorfds: *fd_set,
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timeout: *libc::timeval) -> libc::c_int;
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pub fn gettimeofday(timeval: *mut libc::timeval,
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tzp: *libc::c_void) -> libc::c_int;
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}
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}
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#[cfg(target_os = "android")]
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#[cfg(target_os = "freebsd")]
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#[cfg(target_os = "linux")]
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mod imp {
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use libc;
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use std::uint;
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pub static FD_SETSIZE: uint = 1024;
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pub struct fd_set {
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fds_bits: [uint, ..(FD_SETSIZE / uint::BITS)]
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}
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pub fn fd_set(set: &mut fd_set, fd: i32) {
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let fd = fd as uint;
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set.fds_bits[fd / uint::BITS] |= 1 << (fd % uint::BITS);
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}
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extern {
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pub fn select(nfds: libc::c_int,
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readfds: *fd_set,
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writefds: *fd_set,
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errorfds: *fd_set,
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timeout: *libc::timeval) -> libc::c_int;
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pub fn gettimeofday(timeval: *mut libc::timeval,
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tzp: *libc::c_void) -> libc::c_int;
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}
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}
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