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/
timer_timerfd.rs
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/
timer_timerfd.rs
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// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Timers based on timerfd_create(2)
//!
//! On OSes which support timerfd_create, we can use these much more accurate
//! timers over select() + a timeout (see timer_other.rs). This strategy still
//! employs a worker thread which does the waiting on the timer fds (to send
//! messages away).
//!
//! The worker thread in this implementation uses epoll(7) to block. It
//! maintains a working set of *all* native timers in the process, along with a
//! pipe file descriptor used to communicate that there is data available on the
//! incoming channel to the worker thread. Timers send requests to update their
//! timerfd settings to the worker thread (see the comment above 'oneshot' for
//! why).
//!
//! As with timer_other, timers just using sleep() do not use the timerfd at
//! all. They remove the timerfd from the worker thread and then invoke usleep()
//! to block the calling thread.
//!
//! As with timer_other, all units in this file are in units of millseconds.
use std::comm::Data;
use std::libc;
use std::ptr;
use std::os;
use std::rt::rtio;
use std::hashmap::HashMap;
use std::unstable::intrinsics;
use io::file::FileDesc;
use io::IoResult;
use io::timer_helper;
pub struct Timer {
priv fd: FileDesc,
priv on_worker: bool,
}
pub enum Req {
NewTimer(libc::c_int, Chan<()>, bool, imp::itimerspec),
RemoveTimer(libc::c_int, Chan<()>),
Shutdown,
}
fn helper(input: libc::c_int, messages: Port<Req>) {
let efd = unsafe { imp::epoll_create(10) };
let _fd1 = FileDesc::new(input, true);
let _fd2 = FileDesc::new(efd, true);
fn add(efd: libc::c_int, fd: libc::c_int) {
let event = imp::epoll_event {
events: imp::EPOLLIN as u32,
data: imp::epoll_data_t { fd: fd, pad: 0, }
};
let ret = unsafe {
imp::epoll_ctl(efd, imp::EPOLL_CTL_ADD, fd, &event)
};
assert_eq!(ret, 0);
}
fn del(efd: libc::c_int, fd: libc::c_int) {
let event = imp::epoll_event {
events: 0, data: imp::epoll_data_t { fd: 0, pad: 0, }
};
let ret = unsafe {
imp::epoll_ctl(efd, imp::EPOLL_CTL_DEL, fd, &event)
};
assert_eq!(ret, 0);
}
add(efd, input);
let events: [imp::epoll_event, ..16] = unsafe { intrinsics::init() };
let mut map: HashMap<libc::c_int, (Chan<()>, bool)> = HashMap::new();
'outer: loop {
let n = match unsafe {
imp::epoll_wait(efd, events.as_ptr(),
events.len() as libc::c_int, -1)
} {
0 => fail!("epoll_wait returned immediately!"),
-1 if os::errno() == libc::EINTR as int => { continue }
-1 => fail!("epoll wait failed: {}", os::last_os_error()),
n => n
};
let mut incoming = false;
debug!("{} events to process", n);
for event in events.slice_to(n as uint).iter() {
let fd = event.data.fd;
debug!("data on fd {} (input = {})", fd, input);
if fd == input {
let mut buf = [0, ..1];
// drain the input file descriptor of its input
FileDesc::new(fd, false).inner_read(buf).unwrap();
incoming = true;
} else {
let mut bits = [0, ..8];
// drain the timerfd of how many times its fired
//
// FIXME: should this perform a send() this number of
// times?
FileDesc::new(fd, false).inner_read(bits).unwrap();
let remove = {
match map.find(&fd).expect("fd unregistered") {
&(ref c, oneshot) => !c.try_send(()) || oneshot
}
};
if remove {
map.remove(&fd);
del(efd, fd);
}
}
}
while incoming {
match messages.try_recv() {
Data(NewTimer(fd, chan, one, timeval)) => {
// acknowledge we have the new channel, we will never send
// another message to the old channel
chan.send(());
// If we haven't previously seen the file descriptor, then
// we need to add it to the epoll set.
if map.insert(fd, (chan, one)) {
add(efd, fd);
}
// Update the timerfd's time value now that we have control
// of the timerfd
let ret = unsafe {
imp::timerfd_settime(fd, 0, &timeval, ptr::null())
};
assert_eq!(ret, 0);
}
Data(RemoveTimer(fd, chan)) => {
if map.remove(&fd) {
del(efd, fd);
}
chan.send(());
}
Data(Shutdown) => {
assert!(map.len() == 0);
break 'outer;
}
_ => break,
}
}
}
}
impl Timer {
pub fn new() -> IoResult<Timer> {
timer_helper::boot(helper);
match unsafe { imp::timerfd_create(imp::CLOCK_MONOTONIC, 0) } {
-1 => Err(super::last_error()),
n => Ok(Timer { fd: FileDesc::new(n, true), on_worker: false, }),
}
}
pub fn sleep(ms: u64) {
unsafe { libc::usleep((ms * 1000) as libc::c_uint); }
}
fn remove(&mut self) {
if !self.on_worker { return }
let (p, c) = Chan::new();
timer_helper::send(RemoveTimer(self.fd.fd(), c));
p.recv();
self.on_worker = false;
}
}
impl rtio::RtioTimer for Timer {
fn sleep(&mut self, msecs: u64) {
self.remove();
Timer::sleep(msecs);
}
// Periodic and oneshot channels are updated by updating the settings on the
// corresopnding timerfd. The update is not performed on the thread calling
// oneshot or period, but rather the helper epoll thread. The reason for
// this is to avoid losing messages and avoid leaking messages across ports.
//
// By updating the timerfd on the helper thread, we're guaranteed that all
// messages for a particular setting of the timer will be received by the
// new channel/port pair rather than leaking old messages onto the new port
// or leaking new messages onto the old port.
//
// We also wait for the remote thread to actually receive the new settings
// before returning to guarantee the invariant that when oneshot() and
// period() return that the old port will never receive any more messages.
fn oneshot(&mut self, msecs: u64) -> Port<()> {
let (p, c) = Chan::new();
let new_value = imp::itimerspec {
it_interval: imp::timespec { tv_sec: 0, tv_nsec: 0 },
it_value: imp::timespec {
tv_sec: (msecs / 1000) as libc::time_t,
tv_nsec: ((msecs % 1000) * 1000000) as libc::c_long,
}
};
timer_helper::send(NewTimer(self.fd.fd(), c, true, new_value));
p.recv();
self.on_worker = true;
return p;
}
fn period(&mut self, msecs: u64) -> Port<()> {
let (p, c) = Chan::new();
let spec = imp::timespec {
tv_sec: (msecs / 1000) as libc::time_t,
tv_nsec: ((msecs % 1000) * 1000000) as libc::c_long,
};
let new_value = imp::itimerspec { it_interval: spec, it_value: spec, };
timer_helper::send(NewTimer(self.fd.fd(), c, false, new_value));
p.recv();
self.on_worker = true;
return p;
}
}
impl Drop for Timer {
fn drop(&mut self) {
// When the timerfd file descriptor is closed, it will be automatically
// removed from the epoll set of the worker thread, but we want to make
// sure that the associated channel is also removed from the worker's
// hash map.
self.remove();
}
}
#[allow(dead_code)]
mod imp {
use std::libc;
pub static CLOCK_MONOTONIC: libc::c_int = 1;
pub static EPOLL_CTL_ADD: libc::c_int = 1;
pub static EPOLL_CTL_DEL: libc::c_int = 2;
pub static EPOLL_CTL_MOD: libc::c_int = 3;
pub static EPOLLIN: libc::c_int = 0x001;
pub static EPOLLOUT: libc::c_int = 0x004;
pub static EPOLLPRI: libc::c_int = 0x002;
pub static EPOLLERR: libc::c_int = 0x008;
pub static EPOLLRDHUP: libc::c_int = 0x2000;
pub static EPOLLET: libc::c_int = 1 << 31;
pub static EPOLLHUP: libc::c_int = 0x010;
pub static EPOLLONESHOT: libc::c_int = 1 << 30;
pub struct epoll_event {
events: u32,
data: epoll_data_t,
}
pub struct epoll_data_t {
fd: i32,
pad: u32,
}
pub struct timespec {
tv_sec: libc::time_t,
tv_nsec: libc::c_long,
}
pub struct itimerspec {
it_interval: timespec,
it_value: timespec,
}
extern {
pub fn timerfd_create(clockid: libc::c_int,
flags: libc::c_int) -> libc::c_int;
pub fn timerfd_settime(fd: libc::c_int,
flags: libc::c_int,
new_value: *itimerspec,
old_value: *itimerspec) -> libc::c_int;
pub fn timerfd_gettime(fd: libc::c_int,
curr_value: *itimerspec) -> libc::c_int;
pub fn epoll_create(size: libc::c_int) -> libc::c_int;
pub fn epoll_ctl(epfd: libc::c_int,
op: libc::c_int,
fd: libc::c_int,
event: *epoll_event) -> libc::c_int;
pub fn epoll_wait(epfd: libc::c_int,
events: *epoll_event,
maxevents: libc::c_int,
timeout: libc::c_int) -> libc::c_int;
}
}