1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 //! ## The threading model
15 //! An executing Rust program consists of a collection of native OS threads,
16 //! each with their own stack and local state. Threads can be named, and
17 //! provide some built-in support for low-level synchronization.
19 //! Communication between threads can be done through
20 //! [channels], Rust's message-passing types, along with [other forms of thread
21 //! synchronization](../../std/sync/index.html) and shared-memory data
22 //! structures. In particular, types that are guaranteed to be
23 //! threadsafe are easily shared between threads using the
24 //! atomically-reference-counted container, [`Arc`].
26 //! Fatal logic errors in Rust cause *thread panic*, during which
27 //! a thread will unwind the stack, running destructors and freeing
28 //! owned resources. Thread panic is unrecoverable from within
29 //! the panicking thread (i.e. there is no 'try/catch' in Rust), but
30 //! the panic may optionally be detected from a different thread. If
31 //! the main thread panics, the application will exit with a non-zero
34 //! When the main thread of a Rust program terminates, the entire program shuts
35 //! down, even if other threads are still running. However, this module provides
36 //! convenient facilities for automatically waiting for the termination of a
37 //! child thread (i.e., join).
39 //! ## Spawning a thread
41 //! A new thread can be spawned using the [`thread::spawn`][`spawn`] function:
46 //! thread::spawn(move || {
51 //! In this example, the spawned thread is "detached" from the current
52 //! thread. This means that it can outlive its parent (the thread that spawned
53 //! it), unless this parent is the main thread.
55 //! The parent thread can also wait on the completion of the child
56 //! thread; a call to [`spawn`] produces a [`JoinHandle`], which provides
57 //! a `join` method for waiting:
62 //! let child = thread::spawn(move || {
66 //! let res = child.join();
69 //! The [`join`] method returns a [`thread::Result`] containing [`Ok`] of the final
70 //! value produced by the child thread, or [`Err`] of the value given to
71 //! a call to [`panic!`] if the child panicked.
73 //! ## Configuring threads
75 //! A new thread can be configured before it is spawned via the [`Builder`] type,
76 //! which currently allows you to set the name and stack size for the child thread:
79 //! # #![allow(unused_must_use)]
82 //! thread::Builder::new().name("child1".to_string()).spawn(move || {
83 //! println!("Hello, world!");
87 //! ## The `Thread` type
89 //! Threads are represented via the [`Thread`] type, which you can get in one of
92 //! * By spawning a new thread, e.g. using the [`thread::spawn`][`spawn`]
93 //! function, and calling [`thread`][`JoinHandle::thread`] on the [`JoinHandle`].
94 //! * By requesting the current thread, using the [`thread::current`] function.
96 //! The [`thread::current`] function is available even for threads not spawned
97 //! by the APIs of this module.
99 //! ## Blocking support: park and unpark
101 //! Every thread is equipped with some basic low-level blocking support, via the
102 //! [`thread::park`][`park`] function and [`thread::Thread::unpark()`][`unpark`]
103 //! method. [`park`] blocks the current thread, which can then be resumed from
104 //! another thread by calling the [`unpark`] method on the blocked thread's handle.
106 //! Conceptually, each [`Thread`] handle has an associated token, which is
107 //! initially not present:
109 //! * The [`thread::park`][`park`] function blocks the current thread unless or until
110 //! the token is available for its thread handle, at which point it atomically
111 //! consumes the token. It may also return *spuriously*, without consuming the
112 //! token. [`thread::park_timeout`] does the same, but allows specifying a
113 //! maximum time to block the thread for.
115 //! * The [`unpark`] method on a [`Thread`] atomically makes the token available
116 //! if it wasn't already.
118 //! In other words, each [`Thread`] acts a bit like a semaphore with initial count
119 //! 0, except that the semaphore is *saturating* (the count cannot go above 1),
120 //! and can return spuriously.
122 //! The API is typically used by acquiring a handle to the current thread,
123 //! placing that handle in a shared data structure so that other threads can
124 //! find it, and then `park`ing. When some desired condition is met, another
125 //! thread calls [`unpark`] on the handle.
127 //! The motivation for this design is twofold:
129 //! * It avoids the need to allocate mutexes and condvars when building new
130 //! synchronization primitives; the threads already provide basic blocking/signaling.
132 //! * It can be implemented very efficiently on many platforms.
134 //! ## Thread-local storage
136 //! This module also provides an implementation of thread-local storage for Rust
137 //! programs. Thread-local storage is a method of storing data into a global
138 //! variable that each thread in the program will have its own copy of.
139 //! Threads do not share this data, so accesses do not need to be synchronized.
141 //! A thread-local key owns the value it contains and will destroy the value when the
142 //! thread exits. It is created with the [`thread_local!`] macro and can contain any
143 //! value that is `'static` (no borrowed pointers). It provides an accessor function,
144 //! [`with`], that yields a shared reference to the value to the specified
145 //! closure. Thread-local keys allow only shared access to values, as there would be no
146 //! way to guarantee uniqueness if mutable borrows were allowed. Most values
147 //! will want to make use of some form of **interior mutability** through the
148 //! [`Cell`] or [`RefCell`] types.
150 //! [channels]: ../../std/sync/mpsc/index.html
151 //! [`Arc`]: ../../std/sync/struct.Arc.html
152 //! [`spawn`]: ../../std/thread/fn.spawn.html
153 //! [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
154 //! [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
155 //! [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
156 //! [`Result`]: ../../std/result/enum.Result.html
157 //! [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
158 //! [`Err`]: ../../std/result/enum.Result.html#variant.Err
159 //! [`panic!`]: ../../std/macro.panic.html
160 //! [`Builder`]: ../../std/thread/struct.Builder.html
161 //! [`thread::current`]: ../../std/thread/fn.current.html
162 //! [`thread::Result`]: ../../std/thread/type.Result.html
163 //! [`Thread`]: ../../std/thread/struct.Thread.html
164 //! [`park`]: ../../std/thread/fn.park.html
165 //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
166 //! [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
167 //! [`Cell`]: ../cell/struct.Cell.html
168 //! [`RefCell`]: ../cell/struct.RefCell.html
169 //! [`thread_local!`]: ../macro.thread_local.html
170 //! [`with`]: struct.LocalKey.html#method.with
172 #![stable(feature = "rust1", since = "1.0.0")]
175 use cell::UnsafeCell;
176 use ffi::{CStr, CString};
182 use sync::{Mutex, Condvar, Arc};
183 use sys::thread as imp;
184 use sys_common::mutex;
185 use sys_common::thread_info;
186 use sys_common::util;
187 use sys_common::{AsInner, IntoInner};
190 ////////////////////////////////////////////////////////////////////////////////
191 // Thread-local storage
192 ////////////////////////////////////////////////////////////////////////////////
194 #[macro_use] mod local;
196 #[stable(feature = "rust1", since = "1.0.0")]
197 pub use self::local::{LocalKey, LocalKeyState};
199 // The types used by the thread_local! macro to access TLS keys. Note that there
200 // are two types, the "OS" type and the "fast" type. The OS thread local key
201 // type is accessed via platform-specific API calls and is slow, while the fast
202 // key type is accessed via code generated via LLVM, where TLS keys are set up
203 // by the elf linker. Note that the OS TLS type is always available: on macOS
204 // the standard library is compiled with support for older platform versions
205 // where fast TLS was not available; end-user code is compiled with fast TLS
206 // where available, but both are needed.
208 #[unstable(feature = "libstd_thread_internals", issue = "0")]
209 #[cfg(target_thread_local)]
210 #[doc(hidden)] pub use sys::fast_thread_local::Key as __FastLocalKeyInner;
211 #[unstable(feature = "libstd_thread_internals", issue = "0")]
212 #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner;
214 ////////////////////////////////////////////////////////////////////////////////
216 ////////////////////////////////////////////////////////////////////////////////
218 /// Thread configuration. Provides detailed control over the properties
219 /// and behavior of new threads.
226 /// let builder = thread::Builder::new();
228 /// let handler = builder.spawn(|| {
232 /// handler.join().unwrap();
234 #[stable(feature = "rust1", since = "1.0.0")]
237 // A name for the thread-to-be, for identification in panic messages
238 name: Option<String>,
239 // The size of the stack for the spawned thread in bytes
240 stack_size: Option<usize>,
244 /// Generates the base configuration for spawning a thread, from which
245 /// configuration methods can be chained.
252 /// let builder = thread::Builder::new()
253 /// .name("foo".into())
256 /// let handler = builder.spawn(|| {
260 /// handler.join().unwrap();
262 #[stable(feature = "rust1", since = "1.0.0")]
263 pub fn new() -> Builder {
270 /// Names the thread-to-be. Currently the name is used for identification
271 /// only in panic messages.
278 /// let builder = thread::Builder::new()
279 /// .name("foo".into());
281 /// let handler = builder.spawn(|| {
282 /// assert_eq!(thread::current().name(), Some("foo"))
285 /// handler.join().unwrap();
287 #[stable(feature = "rust1", since = "1.0.0")]
288 pub fn name(mut self, name: String) -> Builder {
289 self.name = Some(name);
293 /// Sets the size of the stack (in bytes) for the new thread.
295 /// The actual stack size may be greater than this value if
296 /// the platform specifies minimal stack size.
303 /// let builder = thread::Builder::new().stack_size(32 * 1024);
305 #[stable(feature = "rust1", since = "1.0.0")]
306 pub fn stack_size(mut self, size: usize) -> Builder {
307 self.stack_size = Some(size);
311 /// Spawns a new thread, and returns a join handle for it.
313 /// The child thread may outlive the parent (unless the parent thread
314 /// is the main thread; the whole process is terminated when the main
315 /// thread finishes). The join handle can be used to block on
316 /// termination of the child thread, including recovering its panics.
318 /// For a more complete documentation see [`thread::spawn`][`spawn`].
322 /// Unlike the [`spawn`] free function, this method yields an
323 /// [`io::Result`] to capture any failure to create the thread at
326 /// [`spawn`]: ../../std/thread/fn.spawn.html
327 /// [`io::Result`]: ../../std/io/type.Result.html
334 /// let builder = thread::Builder::new();
336 /// let handler = builder.spawn(|| {
340 /// handler.join().unwrap();
342 #[stable(feature = "rust1", since = "1.0.0")]
343 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
344 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
346 let Builder { name, stack_size } = self;
348 let stack_size = stack_size.unwrap_or(util::min_stack());
350 let my_thread = Thread::new(name);
351 let their_thread = my_thread.clone();
353 let my_packet : Arc<UnsafeCell<Option<Result<T>>>>
354 = Arc::new(UnsafeCell::new(None));
355 let their_packet = my_packet.clone();
358 if let Some(name) = their_thread.cname() {
359 imp::Thread::set_name(name);
362 thread_info::set(imp::guard::current(), their_thread);
363 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f));
364 *their_packet.get() = Some(try_result);
368 Ok(JoinHandle(JoinInner {
370 Some(imp::Thread::new(stack_size, Box::new(main))?)
373 packet: Packet(my_packet),
378 ////////////////////////////////////////////////////////////////////////////////
380 ////////////////////////////////////////////////////////////////////////////////
382 /// Spawns a new thread, returning a [`JoinHandle`] for it.
384 /// The join handle will implicitly *detach* the child thread upon being
385 /// dropped. In this case, the child thread may outlive the parent (unless
386 /// the parent thread is the main thread; the whole process is terminated when
387 /// the main thread finishes). Additionally, the join handle provides a [`join`]
388 /// method that can be used to join the child thread. If the child thread
389 /// panics, [`join`] will return an [`Err`] containing the argument given to
394 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
395 /// to recover from such errors.
399 /// Simple thread creation.
404 /// let handler = thread::spawn(|| {
408 /// handler.join().unwrap();
411 /// As mentionned in the module documentation, threads are usualy made to
412 /// communicate using [`channel`s][`channels`], here is how it usually looks.
414 /// This example also shows how to use `move`, in order to give ownership
415 /// of values to a thread.
419 /// use std::sync::mpsc::channel;
421 /// let (tx, rx) = channel();
423 /// let sender = thread::spawn(move || {
424 /// tx.send("Hello, thread".to_owned());
427 /// let receiver = thread::spawn(move || {
428 /// println!("{}", rx.recv().unwrap());
435 /// A thread can also return a value through its [`JoinHandle`], you can use
436 /// this to make asynchronous computations (futures might be more appropriate
442 /// let computation = thread::spawn(|| {
443 /// // Some expensive computation.
447 /// let result = computation.join().unwrap();
448 /// println!("{}", v);
451 /// [`channels`]: ../../std/sync/mpsc/index.html
452 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
453 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
454 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
455 /// [`panic`]: ../../std/macro.panic.html
456 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
457 #[stable(feature = "rust1", since = "1.0.0")]
458 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
459 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
461 Builder::new().spawn(f).unwrap()
464 /// Gets a handle to the thread that invokes it.
468 /// Getting a handle to the current thread with `thread::current()`:
473 /// let handler = thread::Builder::new()
474 /// .name("named thread".into())
476 /// let handle = thread::current();
477 /// assert_eq!(handle.name(), Some("named thread"));
481 /// handler.join().unwrap();
483 #[stable(feature = "rust1", since = "1.0.0")]
484 pub fn current() -> Thread {
485 thread_info::current_thread().expect("use of std::thread::current() is not \
486 possible after the thread's local \
487 data has been destroyed")
490 /// Cooperatively gives up a timeslice to the OS scheduler.
497 /// thread::yield_now();
499 #[stable(feature = "rust1", since = "1.0.0")]
501 imp::Thread::yield_now()
504 /// Determines whether the current thread is unwinding because of panic.
511 /// struct SomeStruct;
513 /// impl Drop for SomeStruct {
514 /// fn drop(&mut self) {
515 /// if thread::panicking() {
516 /// println!("dropped while unwinding");
518 /// println!("dropped while not unwinding");
525 /// let a = SomeStruct;
530 /// let b = SomeStruct;
535 #[stable(feature = "rust1", since = "1.0.0")]
536 pub fn panicking() -> bool {
537 panicking::panicking()
540 /// Puts the current thread to sleep for the specified amount of time.
542 /// The thread may sleep longer than the duration specified due to scheduling
543 /// specifics or platform-dependent functionality.
545 /// # Platform behavior
547 /// On Unix platforms this function will not return early due to a
548 /// signal being received or a spurious wakeup.
555 /// // Let's sleep for 2 seconds:
556 /// thread::sleep_ms(2000);
558 #[stable(feature = "rust1", since = "1.0.0")]
559 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
560 pub fn sleep_ms(ms: u32) {
561 sleep(Duration::from_millis(ms as u64))
564 /// Puts the current thread to sleep for the specified amount of time.
566 /// The thread may sleep longer than the duration specified due to scheduling
567 /// specifics or platform-dependent functionality.
569 /// # Platform behavior
571 /// On Unix platforms this function will not return early due to a
572 /// signal being received or a spurious wakeup. Platforms which do not support
573 /// nanosecond precision for sleeping will have `dur` rounded up to the nearest
574 /// granularity of time they can sleep for.
579 /// use std::{thread, time};
581 /// let ten_millis = time::Duration::from_millis(10);
582 /// let now = time::Instant::now();
584 /// thread::sleep(ten_millis);
586 /// assert!(now.elapsed() >= ten_millis);
588 #[stable(feature = "thread_sleep", since = "1.4.0")]
589 pub fn sleep(dur: Duration) {
590 imp::Thread::sleep(dur)
593 /// Blocks unless or until the current thread's token is made available.
595 /// Every thread is equipped with some basic low-level blocking support, via
596 /// the `park()` function and the [`unpark`][unpark] method. These can be
597 /// used as a more CPU-efficient implementation of a spinlock.
599 /// [unpark]: struct.Thread.html#method.unpark
601 /// The API is typically used by acquiring a handle to the current thread,
602 /// placing that handle in a shared data structure so that other threads can
603 /// find it, and then parking (in a loop with a check for the token actually
606 /// A call to `park` does not guarantee that the thread will remain parked
607 /// forever, and callers should be prepared for this possibility.
609 /// See the [module documentation][thread] for more detail.
611 /// [thread]: index.html
613 // The implementation currently uses the trivial strategy of a Mutex+Condvar
614 // with wakeup flag, which does not actually allow spurious wakeups. In the
615 // future, this will be implemented in a more efficient way, perhaps along the lines of
616 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
617 // or futuxes, and in either case may allow spurious wakeups.
618 #[stable(feature = "rust1", since = "1.0.0")]
620 let thread = current();
621 let mut guard = thread.inner.lock.lock().unwrap();
623 guard = thread.inner.cvar.wait(guard).unwrap();
628 /// Use [park_timeout].
630 /// Blocks unless or until the current thread's token is made available or
631 /// the specified duration has been reached (may wake spuriously).
633 /// The semantics of this function are equivalent to `park()` except that the
634 /// thread will be blocked for roughly no longer than `ms`. This method
635 /// should not be used for precise timing due to anomalies such as
636 /// preemption or platform differences that may not cause the maximum
637 /// amount of time waited to be precisely `ms` long.
639 /// See the [module documentation][thread] for more detail.
641 /// [thread]: index.html
642 /// [park_timeout]: fn.park_timeout.html
643 #[stable(feature = "rust1", since = "1.0.0")]
644 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
645 pub fn park_timeout_ms(ms: u32) {
646 park_timeout(Duration::from_millis(ms as u64))
649 /// Blocks unless or until the current thread's token is made available or
650 /// the specified duration has been reached (may wake spuriously).
652 /// The semantics of this function are equivalent to `park()` except that the
653 /// thread will be blocked for roughly no longer than `dur`. This method
654 /// should not be used for precise timing due to anomalies such as
655 /// preemption or platform differences that may not cause the maximum
656 /// amount of time waited to be precisely `dur` long.
658 /// See the module doc for more detail.
660 /// # Platform behavior
662 /// Platforms which do not support nanosecond precision for sleeping will have
663 /// `dur` rounded up to the nearest granularity of time they can sleep for.
667 /// Waiting for the complete expiration of the timeout:
670 /// use std::thread::park_timeout;
671 /// use std::time::{Instant, Duration};
673 /// let timeout = Duration::from_secs(2);
674 /// let beginning_park = Instant::now();
675 /// park_timeout(timeout);
677 /// while beginning_park.elapsed() < timeout {
678 /// println!("restarting park_timeout after {:?}", beginning_park.elapsed());
679 /// let timeout = timeout - beginning_park.elapsed();
680 /// park_timeout(timeout);
683 #[stable(feature = "park_timeout", since = "1.4.0")]
684 pub fn park_timeout(dur: Duration) {
685 let thread = current();
686 let mut guard = thread.inner.lock.lock().unwrap();
688 let (g, _) = thread.inner.cvar.wait_timeout(guard, dur).unwrap();
694 ////////////////////////////////////////////////////////////////////////////////
696 ////////////////////////////////////////////////////////////////////////////////
698 /// A unique identifier for a running thread.
700 /// A `ThreadId` is an opaque object that has a unique value for each thread
701 /// that creates one. `ThreadId`s are not guaranteed to correspond to a thread's
702 /// system-designated identifier.
707 /// #![feature(thread_id)]
711 /// let other_thread = thread::spawn(|| {
712 /// thread::current().id()
715 /// let other_thread_id = other_thread.join().unwrap();
716 /// assert!(thread::current().id() != other_thread_id);
718 #[unstable(feature = "thread_id", issue = "21507")]
719 #[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
720 pub struct ThreadId(u64);
723 // Generate a new unique thread ID.
724 fn new() -> ThreadId {
725 static GUARD: mutex::Mutex = mutex::Mutex::new();
726 static mut COUNTER: u64 = 0;
731 // If we somehow use up all our bits, panic so that we're not
732 // covering up subtle bugs of IDs being reused.
733 if COUNTER == ::u64::MAX {
735 panic!("failed to generate unique thread ID: bitspace exhausted");
748 ////////////////////////////////////////////////////////////////////////////////
750 ////////////////////////////////////////////////////////////////////////////////
752 /// The internal representation of a `Thread` handle
754 name: Option<CString>, // Guaranteed to be UTF-8
756 lock: Mutex<bool>, // true when there is a buffered unpark
761 #[stable(feature = "rust1", since = "1.0.0")]
762 /// A handle to a thread.
764 /// You can use it to identify a thread (by name, for example). Most of the
765 /// time, there is no need to directly create a `Thread` struct using the
766 /// constructor, instead you should use a function like `spawn` to create
767 /// new threads, see the docs of [`Builder`] and [`spawn`] for more.
772 /// # // Note that this example isn't executed by default because it causes
773 /// # // deadlocks on Windows unfortunately (see #25824)
774 /// use std::thread::Builder;
777 /// let thread_name = format!("thread_{}", i);
779 /// .name(thread_name) // Now you can identify which thread panicked
780 /// // thanks to the handle's name
783 /// panic!("I'm scared!!!");
789 /// [`Builder`]: ../../std/thread/struct.Builder.html
790 /// [`spawn`]: ../../std/thread/fn.spawn.html
797 // Used only internally to construct a thread object without spawning
798 pub(crate) fn new(name: Option<String>) -> Thread {
799 let cname = name.map(|n| {
800 CString::new(n).expect("thread name may not contain interior null bytes")
803 inner: Arc::new(Inner {
806 lock: Mutex::new(false),
807 cvar: Condvar::new(),
812 /// Atomically makes the handle's token available if it is not already.
814 /// See the module doc for more detail.
821 /// let handler = thread::Builder::new()
823 /// let thread = thread::current();
828 /// handler.join().unwrap();
830 #[stable(feature = "rust1", since = "1.0.0")]
831 pub fn unpark(&self) {
832 let mut guard = self.inner.lock.lock().unwrap();
835 self.inner.cvar.notify_one();
839 /// Gets the thread's unique identifier.
844 /// #![feature(thread_id)]
848 /// let other_thread = thread::spawn(|| {
849 /// thread::current().id()
852 /// let other_thread_id = other_thread.join().unwrap();
853 /// assert!(thread::current().id() != other_thread_id);
855 #[unstable(feature = "thread_id", issue = "21507")]
856 pub fn id(&self) -> ThreadId {
860 /// Gets the thread's name.
864 /// Threads by default have no name specified:
869 /// let builder = thread::Builder::new();
871 /// let handler = builder.spawn(|| {
872 /// assert!(thread::current().name().is_none());
875 /// handler.join().unwrap();
878 /// Thread with a specified name:
883 /// let builder = thread::Builder::new()
884 /// .name("foo".into());
886 /// let handler = builder.spawn(|| {
887 /// assert_eq!(thread::current().name(), Some("foo"))
890 /// handler.join().unwrap();
892 #[stable(feature = "rust1", since = "1.0.0")]
893 pub fn name(&self) -> Option<&str> {
894 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } )
897 fn cname(&self) -> Option<&CStr> {
898 self.inner.name.as_ref().map(|s| &**s)
902 #[stable(feature = "rust1", since = "1.0.0")]
903 impl fmt::Debug for Thread {
904 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
905 fmt::Debug::fmt(&self.name(), f)
909 ////////////////////////////////////////////////////////////////////////////////
911 ////////////////////////////////////////////////////////////////////////////////
913 /// A specialized [`Result`] type for threads.
915 /// Indicates the manner in which a thread exited.
917 /// A thread that completes without panicking is considered to exit successfully.
925 /// fn copy_in_thread() -> thread::Result<()> {
926 /// thread::spawn(move || { fs::copy("foo.txt", "bar.txt").unwrap(); }).join()
930 /// match copy_in_thread() {
931 /// Ok(_) => println!("this is fine"),
932 /// Err(_) => println!("thread panicked"),
937 /// [`Result`]: ../../std/result/enum.Result.html
938 #[stable(feature = "rust1", since = "1.0.0")]
939 pub type Result<T> = ::result::Result<T, Box<Any + Send + 'static>>;
941 // This packet is used to communicate the return value between the child thread
942 // and the parent thread. Memory is shared through the `Arc` within and there's
943 // no need for a mutex here because synchronization happens with `join()` (the
944 // parent thread never reads this packet until the child has exited).
946 // This packet itself is then stored into a `JoinInner` which in turns is placed
947 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
948 // manually worry about impls like Send and Sync. The type `T` should
949 // already always be Send (otherwise the thread could not have been created) and
950 // this type is inherently Sync because no methods take &self. Regardless,
951 // however, we add inheriting impls for Send/Sync to this type to ensure it's
952 // Send/Sync and that future modifications will still appropriately classify it.
953 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
955 unsafe impl<T: Send> Send for Packet<T> {}
956 unsafe impl<T: Sync> Sync for Packet<T> {}
958 /// Inner representation for JoinHandle
959 struct JoinInner<T> {
960 native: Option<imp::Thread>,
965 impl<T> JoinInner<T> {
966 fn join(&mut self) -> Result<T> {
967 self.native.take().unwrap().join();
969 (*self.packet.0.get()).take().unwrap()
974 /// An owned permission to join on a thread (block on its termination).
976 /// A `JoinHandle` *detaches* the child thread when it is dropped.
978 /// Due to platform restrictions, it is not possible to [`Clone`] this
979 /// handle: the ability to join a child thread is a uniquely-owned
982 /// This `struct` is created by the [`thread::spawn`] function and the
983 /// [`thread::Builder::spawn`] method.
987 /// Creation from [`thread::spawn`]:
992 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
993 /// // some work here
997 /// Creation from [`thread::Builder::spawn`]:
1000 /// use std::thread;
1002 /// let builder = thread::Builder::new();
1004 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1005 /// // some work here
1009 /// [`Clone`]: ../../std/clone/trait.Clone.html
1010 /// [`thread::spawn`]: fn.spawn.html
1011 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
1012 #[stable(feature = "rust1", since = "1.0.0")]
1013 pub struct JoinHandle<T>(JoinInner<T>);
1015 impl<T> JoinHandle<T> {
1016 /// Extracts a handle to the underlying thread.
1021 /// #![feature(thread_id)]
1023 /// use std::thread;
1025 /// let builder = thread::Builder::new();
1027 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1028 /// // some work here
1031 /// let thread = join_handle.thread();
1032 /// println!("thread id: {:?}", thread.id());
1034 #[stable(feature = "rust1", since = "1.0.0")]
1035 pub fn thread(&self) -> &Thread {
1039 /// Waits for the associated thread to finish.
1041 /// If the child thread panics, [`Err`] is returned with the parameter given
1044 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
1045 /// [`panic`]: ../../std/macro.panic.html
1050 /// use std::thread;
1052 /// let builder = thread::Builder::new();
1054 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1055 /// // some work here
1057 /// join_handle.join().expect("Couldn't join on the associated thread");
1059 #[stable(feature = "rust1", since = "1.0.0")]
1060 pub fn join(mut self) -> Result<T> {
1065 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
1066 fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() }
1069 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1070 fn into_inner(self) -> imp::Thread { self.0.native.unwrap() }
1073 #[stable(feature = "std_debug", since = "1.16.0")]
1074 impl<T> fmt::Debug for JoinHandle<T> {
1075 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1076 f.pad("JoinHandle { .. }")
1080 fn _assert_sync_and_send() {
1081 fn _assert_both<T: Send + Sync>() {}
1082 _assert_both::<JoinHandle<()>>();
1083 _assert_both::<Thread>();
1086 ////////////////////////////////////////////////////////////////////////////////
1088 ////////////////////////////////////////////////////////////////////////////////
1090 #[cfg(all(test, not(target_os = "emscripten")))]
1093 use sync::mpsc::{channel, Sender};
1095 use super::{Builder};
1100 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1101 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1104 fn test_unnamed_thread() {
1105 thread::spawn(move|| {
1106 assert!(thread::current().name().is_none());
1107 }).join().ok().unwrap();
1111 fn test_named_thread() {
1112 Builder::new().name("ada lovelace".to_string()).spawn(move|| {
1113 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1114 }).unwrap().join().unwrap();
1119 fn test_invalid_named_thread() {
1120 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1124 fn test_run_basic() {
1125 let (tx, rx) = channel();
1126 thread::spawn(move|| {
1127 tx.send(()).unwrap();
1133 fn test_join_panic() {
1134 match thread::spawn(move|| {
1137 result::Result::Err(_) => (),
1138 result::Result::Ok(()) => panic!()
1143 fn test_spawn_sched() {
1144 let (tx, rx) = channel();
1146 fn f(i: i32, tx: Sender<()>) {
1147 let tx = tx.clone();
1148 thread::spawn(move|| {
1150 tx.send(()).unwrap();
1162 fn test_spawn_sched_childs_on_default_sched() {
1163 let (tx, rx) = channel();
1165 thread::spawn(move|| {
1166 thread::spawn(move|| {
1167 tx.send(()).unwrap();
1174 fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<Fn() + Send>) {
1175 let (tx, rx) = channel();
1177 let x: Box<_> = box 1;
1178 let x_in_parent = (&*x) as *const i32 as usize;
1180 spawnfn(Box::new(move|| {
1181 let x_in_child = (&*x) as *const i32 as usize;
1182 tx.send(x_in_child).unwrap();
1185 let x_in_child = rx.recv().unwrap();
1186 assert_eq!(x_in_parent, x_in_child);
1190 fn test_avoid_copying_the_body_spawn() {
1191 avoid_copying_the_body(|v| {
1192 thread::spawn(move || v());
1197 fn test_avoid_copying_the_body_thread_spawn() {
1198 avoid_copying_the_body(|f| {
1199 thread::spawn(move|| {
1206 fn test_avoid_copying_the_body_join() {
1207 avoid_copying_the_body(|f| {
1208 let _ = thread::spawn(move|| {
1215 fn test_child_doesnt_ref_parent() {
1216 // If the child refcounts the parent thread, this will stack overflow when
1217 // climbing the thread tree to dereference each ancestor. (See #1789)
1218 // (well, it would if the constant were 8000+ - I lowered it to be more
1219 // valgrind-friendly. try this at home, instead..!)
1220 const GENERATIONS: u32 = 16;
1221 fn child_no(x: u32) -> Box<Fn() + Send> {
1222 return Box::new(move|| {
1223 if x < GENERATIONS {
1224 thread::spawn(move|| child_no(x+1)());
1228 thread::spawn(|| child_no(0)());
1232 fn test_simple_newsched_spawn() {
1233 thread::spawn(move || {});
1237 fn test_try_panic_message_static_str() {
1238 match thread::spawn(move|| {
1239 panic!("static string");
1242 type T = &'static str;
1243 assert!(e.is::<T>());
1244 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1251 fn test_try_panic_message_owned_str() {
1252 match thread::spawn(move|| {
1253 panic!("owned string".to_string());
1257 assert!(e.is::<T>());
1258 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1265 fn test_try_panic_message_any() {
1266 match thread::spawn(move|| {
1267 panic!(box 413u16 as Box<Any + Send>);
1270 type T = Box<Any + Send>;
1271 assert!(e.is::<T>());
1272 let any = e.downcast::<T>().unwrap();
1273 assert!(any.is::<u16>());
1274 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1281 fn test_try_panic_message_unit_struct() {
1284 match thread::spawn(move|| {
1287 Err(ref e) if e.is::<Juju>() => {}
1288 Err(_) | Ok(()) => panic!()
1293 fn test_park_timeout_unpark_before() {
1295 thread::current().unpark();
1296 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1301 fn test_park_timeout_unpark_not_called() {
1303 thread::park_timeout(Duration::from_millis(10));
1308 fn test_park_timeout_unpark_called_other_thread() {
1310 let th = thread::current();
1312 let _guard = thread::spawn(move || {
1313 super::sleep(Duration::from_millis(50));
1317 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1322 fn sleep_ms_smoke() {
1323 thread::sleep(Duration::from_millis(2));
1327 fn test_thread_id_equal() {
1328 assert!(thread::current().id() == thread::current().id());
1332 fn test_thread_id_not_equal() {
1333 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1334 assert!(thread::current().id() != spawned_id);
1337 // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due
1338 // to the test harness apparently interfering with stderr configuration.