mio/poll.rs
1#[cfg(all(
2 unix,
3 not(mio_unsupported_force_poll_poll),
4 not(any(target_os = "solaris", target_os = "vita"))
5))]
6use std::os::unix::io::{AsRawFd, RawFd};
7#[cfg(all(debug_assertions, not(target_os = "wasi")))]
8use std::sync::atomic::{AtomicBool, Ordering};
9#[cfg(all(debug_assertions, not(target_os = "wasi")))]
10use std::sync::Arc;
11use std::time::Duration;
12use std::{fmt, io};
13
14use crate::{event, sys, Events, Interest, Token};
15
16/// Polls for readiness events on all registered values.
17///
18/// `Poll` allows a program to monitor a large number of [`event::Source`]s,
19/// waiting until one or more become "ready" for some class of operations; e.g.
20/// reading and writing. An event source is considered ready if it is possible
21/// to immediately perform a corresponding operation; e.g. [`read`] or
22/// [`write`].
23///
24/// To use `Poll`, an `event::Source` must first be registered with the `Poll`
25/// instance using the [`register`] method on its associated `Register`,
26/// supplying readiness interest. The readiness interest tells `Poll` which
27/// specific operations on the handle to monitor for readiness. A `Token` is
28/// also passed to the [`register`] function. When `Poll` returns a readiness
29/// event, it will include this token. This associates the event with the
30/// event source that generated the event.
31///
32/// [`event::Source`]: ./event/trait.Source.html
33/// [`read`]: ./net/struct.TcpStream.html#method.read
34/// [`write`]: ./net/struct.TcpStream.html#method.write
35/// [`register`]: struct.Registry.html#method.register
36///
37/// # Examples
38///
39/// A basic example -- establishing a `TcpStream` connection.
40///
41#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
42#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
43/// # use std::error::Error;
44/// # fn main() -> Result<(), Box<dyn Error>> {
45/// use mio::{Events, Poll, Interest, Token};
46/// use mio::net::TcpStream;
47///
48/// use std::net::{self, SocketAddr};
49///
50/// // Bind a server socket to connect to.
51/// let addr: SocketAddr = "127.0.0.1:0".parse()?;
52/// let server = net::TcpListener::bind(addr)?;
53///
54/// // Construct a new `Poll` handle as well as the `Events` we'll store into
55/// let mut poll = Poll::new()?;
56/// let mut events = Events::with_capacity(1024);
57///
58/// // Connect the stream
59/// let mut stream = TcpStream::connect(server.local_addr()?)?;
60///
61/// // Register the stream with `Poll`
62/// poll.registry().register(&mut stream, Token(0), Interest::READABLE | Interest::WRITABLE)?;
63///
64/// // Wait for the socket to become ready. This has to happens in a loop to
65/// // handle spurious wakeups.
66/// loop {
67/// poll.poll(&mut events, None)?;
68///
69/// for event in &events {
70/// if event.token() == Token(0) && event.is_writable() {
71/// // The socket connected (probably, it could still be a spurious
72/// // wakeup)
73/// return Ok(());
74/// }
75/// }
76/// }
77/// # }
78/// ```
79///
80/// # Portability
81///
82/// Using `Poll` provides a portable interface across supported platforms as
83/// long as the caller takes the following into consideration:
84///
85/// ### Spurious events
86///
87/// [`Poll::poll`] may return readiness events even if the associated
88/// event source is not actually ready. Given the same code, this may
89/// happen more on some platforms than others. It is important to never assume
90/// that, just because a readiness event was received, that the associated
91/// operation will succeed as well.
92///
93/// If operation fails with [`WouldBlock`], then the caller should not treat
94/// this as an error, but instead should wait until another readiness event is
95/// received.
96///
97/// ### Draining readiness
98///
99/// Once a readiness event is received, the corresponding operation must be
100/// performed repeatedly until it returns [`WouldBlock`]. Unless this is done,
101/// there is no guarantee that another readiness event will be delivered, even
102/// if further data is received for the event source.
103///
104/// [`WouldBlock`]: std::io::ErrorKind::WouldBlock
105///
106/// ### Readiness operations
107///
108/// The only readiness operations that are guaranteed to be present on all
109/// supported platforms are [`readable`] and [`writable`]. All other readiness
110/// operations may have false negatives and as such should be considered
111/// **hints**. This means that if a socket is registered with [`readable`]
112/// interest and either an error or close is received, a readiness event will
113/// be generated for the socket, but it **may** only include `readable`
114/// readiness. Also note that, given the potential for spurious events,
115/// receiving a readiness event with `read_closed`, `write_closed`, or `error`
116/// doesn't actually mean that a `read` on the socket will return a result
117/// matching the readiness event.
118///
119/// In other words, portable programs that explicitly check for [`read_closed`],
120/// [`write_closed`], or [`error`] readiness should be doing so as an
121/// **optimization** and always be able to handle an error or close situation
122/// when performing the actual read operation.
123///
124/// [`readable`]: ./event/struct.Event.html#method.is_readable
125/// [`writable`]: ./event/struct.Event.html#method.is_writable
126/// [`error`]: ./event/struct.Event.html#method.is_error
127/// [`read_closed`]: ./event/struct.Event.html#method.is_read_closed
128/// [`write_closed`]: ./event/struct.Event.html#method.is_write_closed
129///
130/// ### Registering handles
131///
132/// Unless otherwise noted, it should be assumed that types implementing
133/// [`event::Source`] will never become ready unless they are registered with
134/// `Poll`.
135///
136/// For example:
137///
138#[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
139#[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
140/// # use std::error::Error;
141/// # use std::net;
142/// # fn main() -> Result<(), Box<dyn Error>> {
143/// use mio::{Poll, Interest, Token};
144/// use mio::net::TcpStream;
145/// use std::net::SocketAddr;
146/// use std::time::Duration;
147/// use std::thread;
148///
149/// let address: SocketAddr = "127.0.0.1:0".parse()?;
150/// let listener = net::TcpListener::bind(address)?;
151/// let mut sock = TcpStream::connect(listener.local_addr()?)?;
152///
153/// thread::sleep(Duration::from_secs(1));
154///
155/// let poll = Poll::new()?;
156///
157/// // The connect is not guaranteed to have started until it is registered at
158/// // this point
159/// poll.registry().register(&mut sock, Token(0), Interest::READABLE | Interest::WRITABLE)?;
160/// # Ok(())
161/// # }
162/// ```
163///
164/// ### Dropping `Poll`
165///
166/// When the `Poll` instance is dropped it may cancel in-flight operations for
167/// the registered [event sources], meaning that no further events for them may
168/// be received. It also means operations on the registered event sources may no
169/// longer work. It is up to the user to keep the `Poll` instance alive while
170/// registered event sources are being used.
171///
172/// [event sources]: ./event/trait.Source.html
173///
174/// ### Accessing raw fd/socket/handle
175///
176/// Mio makes it possible for many types to be converted into a raw file
177/// descriptor (fd, Unix), socket (Windows) or handle (Windows). This makes it
178/// possible to support more operations on the type than Mio supports, for
179/// example it makes [mio-aio] possible. However accessing the raw fd is not
180/// without it's pitfalls.
181///
182/// Specifically performing I/O operations outside of Mio on these types (via
183/// the raw fd) has unspecified behaviour. It could cause no more events to be
184/// generated for the type even though it returned `WouldBlock` (in an operation
185/// directly accessing the fd). The behaviour is OS specific and Mio can only
186/// guarantee cross-platform behaviour if it can control the I/O.
187///
188/// [mio-aio]: https://github.com/asomers/mio-aio
189///
190/// *The following is **not** guaranteed, just a description of the current
191/// situation!* Mio is allowed to change the following without it being considered
192/// a breaking change, don't depend on this, it's just here to inform the user.
193/// Currently the kqueue and epoll implementation support direct I/O operations
194/// on the fd without Mio's knowledge. Windows however needs **all** I/O
195/// operations to go through Mio otherwise it is not able to update it's
196/// internal state properly and won't generate events.
197///
198/// ### Polling without registering event sources
199///
200///
201/// *The following is **not** guaranteed, just a description of the current
202/// situation!* Mio is allowed to change the following without it being
203/// considered a breaking change, don't depend on this, it's just here to inform
204/// the user. On platforms that use epoll, kqueue or IOCP (see implementation
205/// notes below) polling without previously registering [event sources] will
206/// result in sleeping forever, only a process signal will be able to wake up
207/// the thread.
208///
209/// On WASM/WASI this is different as it doesn't support process signals,
210/// furthermore the WASI specification doesn't specify a behaviour in this
211/// situation, thus it's up to the implementation what to do here. As an
212/// example, the wasmtime runtime will return `EINVAL` in this situation, but
213/// different runtimes may return different results. If you have further
214/// insights or thoughts about this situation (and/or how Mio should handle it)
215/// please add you comment to [pull request#1580].
216///
217/// [event sources]: crate::event::Source
218/// [pull request#1580]: https://github.com/tokio-rs/mio/pull/1580
219///
220/// # Implementation notes
221///
222/// `Poll` is backed by the selector provided by the operating system.
223///
224/// | OS | Selector |
225/// |---------------|-----------|
226/// | Android | [epoll] |
227/// | DragonFly BSD | [kqueue] |
228/// | FreeBSD | [kqueue] |
229/// | iOS | [kqueue] |
230/// | illumos | [epoll] |
231/// | Linux | [epoll] |
232/// | NetBSD | [kqueue] |
233/// | OpenBSD | [kqueue] |
234/// | Windows | [IOCP] |
235/// | macOS | [kqueue] |
236///
237/// On all supported platforms, socket operations are handled by using the
238/// system selector. Platform specific extensions (e.g. [`SourceFd`]) allow
239/// accessing other features provided by individual system selectors. For
240/// example, Linux's [`signalfd`] feature can be used by registering the FD with
241/// `Poll` via [`SourceFd`].
242///
243/// On all platforms except windows, a call to [`Poll::poll`] is mostly just a
244/// direct call to the system selector. However, [IOCP] uses a completion model
245/// instead of a readiness model. In this case, `Poll` must adapt the completion
246/// model Mio's API. While non-trivial, the bridge layer is still quite
247/// efficient. The most expensive part being calls to `read` and `write` require
248/// data to be copied into an intermediate buffer before it is passed to the
249/// kernel.
250///
251/// [epoll]: https://man7.org/linux/man-pages/man7/epoll.7.html
252/// [kqueue]: https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2
253/// [IOCP]: https://docs.microsoft.com/en-us/windows/win32/fileio/i-o-completion-ports
254/// [`signalfd`]: https://man7.org/linux/man-pages/man2/signalfd.2.html
255/// [`SourceFd`]: unix/struct.SourceFd.html
256/// [`Poll::poll`]: struct.Poll.html#method.poll
257pub struct Poll {
258 registry: Registry,
259}
260
261/// Registers I/O resources.
262pub struct Registry {
263 selector: sys::Selector,
264 /// Whether this selector currently has an associated waker.
265 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
266 has_waker: Arc<AtomicBool>,
267}
268
269impl Poll {
270 cfg_os_poll! {
271 /// Return a new `Poll` handle.
272 ///
273 /// This function will make a syscall to the operating system to create
274 /// the system selector. If this syscall fails, `Poll::new` will return
275 /// with the error.
276 ///
277 /// close-on-exec flag is set on the file descriptors used by the selector to prevent
278 /// leaking it to executed processes. However, on some systems such as
279 /// old Linux systems that don't support `epoll_create1` syscall it is done
280 /// non-atomically, so a separate thread executing in parallel to this
281 /// function may accidentally leak the file descriptor if it executes a
282 /// new process before this function returns.
283 ///
284 /// See [struct] level docs for more details.
285 ///
286 /// [struct]: struct.Poll.html
287 ///
288 /// # Examples
289 ///
290 /// ```
291 /// # use std::error::Error;
292 /// # fn main() -> Result<(), Box<dyn Error>> {
293 /// use mio::{Poll, Events};
294 /// use std::time::Duration;
295 ///
296 /// let mut poll = match Poll::new() {
297 /// Ok(poll) => poll,
298 /// Err(e) => panic!("failed to create Poll instance; err={:?}", e),
299 /// };
300 ///
301 /// // Create a structure to receive polled events
302 /// let mut events = Events::with_capacity(1024);
303 ///
304 /// // Wait for events, but none will be received because no
305 /// // `event::Source`s have been registered with this `Poll` instance.
306 /// poll.poll(&mut events, Some(Duration::from_millis(500)))?;
307 /// assert!(events.is_empty());
308 /// # Ok(())
309 /// # }
310 /// ```
311 pub fn new() -> io::Result<Poll> {
312 sys::Selector::new().map(|selector| Poll {
313 registry: Registry {
314 selector,
315 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
316 has_waker: Arc::new(AtomicBool::new(false)),
317 },
318 })
319 }
320 }
321
322 /// Create a separate `Registry` which can be used to register
323 /// `event::Source`s.
324 pub fn registry(&self) -> &Registry {
325 &self.registry
326 }
327
328 /// Wait for readiness events
329 ///
330 /// Blocks the current thread and waits for readiness events for any of the
331 /// [`event::Source`]s that have been registered with this `Poll` instance.
332 /// The function will block until either at least one readiness event has
333 /// been received or `timeout` has elapsed. A `timeout` of `None` means that
334 /// `poll` will block until a readiness event has been received.
335 ///
336 /// The supplied `events` will be cleared and newly received readiness events
337 /// will be pushed onto the end. At most `events.capacity()` events will be
338 /// returned. If there are further pending readiness events, they will be
339 /// returned on the next call to `poll`.
340 ///
341 /// A single call to `poll` may result in multiple readiness events being
342 /// returned for a single event source. For example, if a TCP socket becomes
343 /// both readable and writable, it may be possible for a single readiness
344 /// event to be returned with both [`readable`] and [`writable`] readiness
345 /// **OR** two separate events may be returned, one with [`readable`] set
346 /// and one with [`writable`] set.
347 ///
348 /// Note that the `timeout` will be rounded up to the system clock
349 /// granularity (usually 1ms), and kernel scheduling delays mean that
350 /// the blocking interval may be overrun by a small amount.
351 ///
352 /// See the [struct] level documentation for a higher level discussion of
353 /// polling.
354 ///
355 /// [`event::Source`]: ./event/trait.Source.html
356 /// [`readable`]: struct.Interest.html#associatedconstant.READABLE
357 /// [`writable`]: struct.Interest.html#associatedconstant.WRITABLE
358 /// [struct]: struct.Poll.html
359 /// [`iter`]: ./event/struct.Events.html#method.iter
360 ///
361 /// # Notes
362 ///
363 /// This returns any errors without attempting to retry, previous versions
364 /// of Mio would automatically retry the poll call if it was interrupted
365 /// (if `EINTR` was returned).
366 ///
367 /// Currently if the `timeout` elapses without any readiness events
368 /// triggering this will return `Ok(())`. However we're not guaranteeing
369 /// this behaviour as this depends on the OS.
370 ///
371 /// # Examples
372 ///
373 /// A basic example -- establishing a `TcpStream` connection.
374 ///
375 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
376 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
377 /// # use std::error::Error;
378 /// # fn main() -> Result<(), Box<dyn Error>> {
379 /// use mio::{Events, Poll, Interest, Token};
380 /// use mio::net::TcpStream;
381 ///
382 /// use std::net::{TcpListener, SocketAddr};
383 /// use std::thread;
384 ///
385 /// // Bind a server socket to connect to.
386 /// let addr: SocketAddr = "127.0.0.1:0".parse()?;
387 /// let server = TcpListener::bind(addr)?;
388 /// let addr = server.local_addr()?.clone();
389 ///
390 /// // Spawn a thread to accept the socket
391 /// thread::spawn(move || {
392 /// let _ = server.accept();
393 /// });
394 ///
395 /// // Construct a new `Poll` handle as well as the `Events` we'll store into
396 /// let mut poll = Poll::new()?;
397 /// let mut events = Events::with_capacity(1024);
398 ///
399 /// // Connect the stream
400 /// let mut stream = TcpStream::connect(addr)?;
401 ///
402 /// // Register the stream with `Poll`
403 /// poll.registry().register(
404 /// &mut stream,
405 /// Token(0),
406 /// Interest::READABLE | Interest::WRITABLE)?;
407 ///
408 /// // Wait for the socket to become ready. This has to happens in a loop to
409 /// // handle spurious wakeups.
410 /// loop {
411 /// poll.poll(&mut events, None)?;
412 ///
413 /// for event in &events {
414 /// if event.token() == Token(0) && event.is_writable() {
415 /// // The socket connected (probably, it could still be a spurious
416 /// // wakeup)
417 /// return Ok(());
418 /// }
419 /// }
420 /// }
421 /// # }
422 /// ```
423 ///
424 /// [struct]: #
425 pub fn poll(&mut self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> {
426 self.registry.selector.select(events.sys(), timeout)
427 }
428}
429
430#[cfg(all(
431 unix,
432 not(mio_unsupported_force_poll_poll),
433 not(any(target_os = "solaris", target_os = "vita"))
434))]
435impl AsRawFd for Poll {
436 fn as_raw_fd(&self) -> RawFd {
437 self.registry.as_raw_fd()
438 }
439}
440
441impl fmt::Debug for Poll {
442 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
443 fmt.debug_struct("Poll").finish()
444 }
445}
446
447impl Registry {
448 /// Register an [`event::Source`] with the `Poll` instance.
449 ///
450 /// Once registered, the `Poll` instance will monitor the event source for
451 /// readiness state changes. When it notices a state change, it will return
452 /// a readiness event for the handle the next time [`poll`] is called.
453 ///
454 /// See [`Poll`] docs for a high level overview.
455 ///
456 /// # Arguments
457 ///
458 /// `source: &mut S: event::Source`: This is the source of events that the
459 /// `Poll` instance should monitor for readiness state changes.
460 ///
461 /// `token: Token`: The caller picks a token to associate with the socket.
462 /// When [`poll`] returns an event for the handle, this token is included.
463 /// This allows the caller to map the event to its source. The token
464 /// associated with the `event::Source` can be changed at any time by
465 /// calling [`reregister`].
466 ///
467 /// See documentation on [`Token`] for an example showing how to pick
468 /// [`Token`] values.
469 ///
470 /// `interest: Interest`: Specifies which operations `Poll` should monitor
471 /// for readiness. `Poll` will only return readiness events for operations
472 /// specified by this argument.
473 ///
474 /// If a socket is registered with readable interest and the socket becomes
475 /// writable, no event will be returned from [`poll`].
476 ///
477 /// The readiness interest for an `event::Source` can be changed at any time
478 /// by calling [`reregister`].
479 ///
480 /// # Notes
481 ///
482 /// Callers must ensure that if a source being registered with a `Poll`
483 /// instance was previously registered with that `Poll` instance, then a
484 /// call to [`deregister`] has already occurred. Consecutive calls to
485 /// `register` is unspecified behavior.
486 ///
487 /// Unless otherwise specified, the caller should assume that once an event
488 /// source is registered with a `Poll` instance, it is bound to that `Poll`
489 /// instance for the lifetime of the event source. This remains true even
490 /// if the event source is deregistered from the poll instance using
491 /// [`deregister`].
492 ///
493 /// [`event::Source`]: ./event/trait.Source.html
494 /// [`poll`]: struct.Poll.html#method.poll
495 /// [`reregister`]: struct.Registry.html#method.reregister
496 /// [`deregister`]: struct.Registry.html#method.deregister
497 /// [`Token`]: struct.Token.html
498 ///
499 /// # Examples
500 ///
501 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
502 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
503 /// # use std::error::Error;
504 /// # use std::net;
505 /// # fn main() -> Result<(), Box<dyn Error>> {
506 /// use mio::{Events, Poll, Interest, Token};
507 /// use mio::net::TcpStream;
508 /// use std::net::SocketAddr;
509 /// use std::time::{Duration, Instant};
510 ///
511 /// let mut poll = Poll::new()?;
512 ///
513 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
514 /// let listener = net::TcpListener::bind(address)?;
515 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
516 ///
517 /// // Register the socket with `poll`
518 /// poll.registry().register(
519 /// &mut socket,
520 /// Token(0),
521 /// Interest::READABLE | Interest::WRITABLE)?;
522 ///
523 /// let mut events = Events::with_capacity(1024);
524 /// let start = Instant::now();
525 /// let timeout = Duration::from_millis(500);
526 ///
527 /// loop {
528 /// let elapsed = start.elapsed();
529 ///
530 /// if elapsed >= timeout {
531 /// // Connection timed out
532 /// return Ok(());
533 /// }
534 ///
535 /// let remaining = timeout - elapsed;
536 /// poll.poll(&mut events, Some(remaining))?;
537 ///
538 /// for event in &events {
539 /// if event.token() == Token(0) {
540 /// // Something (probably) happened on the socket.
541 /// return Ok(());
542 /// }
543 /// }
544 /// }
545 /// # }
546 /// ```
547 pub fn register<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()>
548 where
549 S: event::Source + ?Sized,
550 {
551 trace!(
552 "registering event source with poller: token={:?}, interests={:?}",
553 token,
554 interests
555 );
556 source.register(self, token, interests)
557 }
558
559 /// Re-register an [`event::Source`] with the `Poll` instance.
560 ///
561 /// Re-registering an event source allows changing the details of the
562 /// registration. Specifically, it allows updating the associated `token`
563 /// and `interests` specified in previous `register` and `reregister` calls.
564 ///
565 /// The `reregister` arguments fully override the previous values. In other
566 /// words, if a socket is registered with [`readable`] interest and the call
567 /// to `reregister` specifies [`writable`], then read interest is no longer
568 /// requested for the handle.
569 ///
570 /// The event source must have previously been registered with this instance
571 /// of `Poll`, otherwise the behavior is unspecified.
572 ///
573 /// See the [`register`] documentation for details about the function
574 /// arguments and see the [`struct`] docs for a high level overview of
575 /// polling.
576 ///
577 /// # Examples
578 ///
579 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
580 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
581 /// # use std::error::Error;
582 /// # use std::net;
583 /// # fn main() -> Result<(), Box<dyn Error>> {
584 /// use mio::{Poll, Interest, Token};
585 /// use mio::net::TcpStream;
586 /// use std::net::SocketAddr;
587 ///
588 /// let poll = Poll::new()?;
589 ///
590 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
591 /// let listener = net::TcpListener::bind(address)?;
592 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
593 ///
594 /// // Register the socket with `poll`, requesting readable
595 /// poll.registry().register(
596 /// &mut socket,
597 /// Token(0),
598 /// Interest::READABLE)?;
599 ///
600 /// // Reregister the socket specifying write interest instead. Even though
601 /// // the token is the same it must be specified.
602 /// poll.registry().reregister(
603 /// &mut socket,
604 /// Token(0),
605 /// Interest::WRITABLE)?;
606 /// # Ok(())
607 /// # }
608 /// ```
609 ///
610 /// [`event::Source`]: ./event/trait.Source.html
611 /// [`struct`]: struct.Poll.html
612 /// [`register`]: struct.Registry.html#method.register
613 /// [`readable`]: ./event/struct.Event.html#is_readable
614 /// [`writable`]: ./event/struct.Event.html#is_writable
615 pub fn reregister<S>(&self, source: &mut S, token: Token, interests: Interest) -> io::Result<()>
616 where
617 S: event::Source + ?Sized,
618 {
619 trace!(
620 "reregistering event source with poller: token={:?}, interests={:?}",
621 token,
622 interests
623 );
624 source.reregister(self, token, interests)
625 }
626
627 /// Deregister an [`event::Source`] with the `Poll` instance.
628 ///
629 /// When an event source is deregistered, the `Poll` instance will no longer
630 /// monitor it for readiness state changes. Deregistering clears up any
631 /// internal resources needed to track the handle. After an explicit call
632 /// to this method completes, it is guaranteed that the token previously
633 /// registered to this handle will not be returned by a future poll, so long
634 /// as a happens-before relationship is established between this call and
635 /// the poll.
636 ///
637 /// The event source must have previously been registered with this instance
638 /// of `Poll`, otherwise the behavior is unspecified.
639 ///
640 /// A handle can be passed back to `register` after it has been
641 /// deregistered; however, it must be passed back to the **same** `Poll`
642 /// instance, otherwise the behavior is unspecified.
643 ///
644 /// # Examples
645 ///
646 #[cfg_attr(all(feature = "os-poll", feature = "net"), doc = "```")]
647 #[cfg_attr(not(all(feature = "os-poll", feature = "net")), doc = "```ignore")]
648 /// # use std::error::Error;
649 /// # use std::net;
650 /// # fn main() -> Result<(), Box<dyn Error>> {
651 /// use mio::{Events, Poll, Interest, Token};
652 /// use mio::net::TcpStream;
653 /// use std::net::SocketAddr;
654 /// use std::time::Duration;
655 ///
656 /// let mut poll = Poll::new()?;
657 ///
658 /// let address: SocketAddr = "127.0.0.1:0".parse()?;
659 /// let listener = net::TcpListener::bind(address)?;
660 /// let mut socket = TcpStream::connect(listener.local_addr()?)?;
661 ///
662 /// // Register the socket with `poll`
663 /// poll.registry().register(
664 /// &mut socket,
665 /// Token(0),
666 /// Interest::READABLE)?;
667 ///
668 /// poll.registry().deregister(&mut socket)?;
669 ///
670 /// let mut events = Events::with_capacity(1024);
671 ///
672 /// // Set a timeout because this poll should never receive any events.
673 /// poll.poll(&mut events, Some(Duration::from_secs(1)))?;
674 /// assert!(events.is_empty());
675 /// # Ok(())
676 /// # }
677 /// ```
678 pub fn deregister<S>(&self, source: &mut S) -> io::Result<()>
679 where
680 S: event::Source + ?Sized,
681 {
682 trace!("deregistering event source from poller");
683 source.deregister(self)
684 }
685
686 /// Creates a new independently owned `Registry`.
687 ///
688 /// Event sources registered with this `Registry` will be registered with
689 /// the original `Registry` and `Poll` instance.
690 pub fn try_clone(&self) -> io::Result<Registry> {
691 self.selector.try_clone().map(|selector| Registry {
692 selector,
693 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
694 has_waker: Arc::clone(&self.has_waker),
695 })
696 }
697
698 /// Internal check to ensure only a single `Waker` is active per [`Poll`]
699 /// instance.
700 #[cfg(all(debug_assertions, not(target_os = "wasi")))]
701 pub(crate) fn register_waker(&self) {
702 assert!(
703 !self.has_waker.swap(true, Ordering::AcqRel),
704 "Only a single `Waker` can be active per `Poll` instance"
705 );
706 }
707
708 /// Get access to the `sys::Selector`.
709 #[cfg(any(not(target_os = "wasi"), feature = "net"))]
710 pub(crate) fn selector(&self) -> &sys::Selector {
711 &self.selector
712 }
713}
714
715impl fmt::Debug for Registry {
716 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
717 fmt.debug_struct("Registry").finish()
718 }
719}
720
721#[cfg(all(
722 unix,
723 not(mio_unsupported_force_poll_poll),
724 not(any(target_os = "solaris", target_os = "vita"))
725))]
726impl AsRawFd for Registry {
727 fn as_raw_fd(&self) -> RawFd {
728 self.selector.as_raw_fd()
729 }
730}
731
732cfg_os_poll! {
733 #[cfg(all(
734 unix,
735 not(mio_unsupported_force_poll_poll),
736 not(any(target_os = "solaris", target_os = "vita")),
737 ))]
738 #[test]
739 pub fn as_raw_fd() {
740 let poll = Poll::new().unwrap();
741 assert!(poll.as_raw_fd() > 0);
742 }
743}