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 [`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()`] 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 //! [`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.spawn.html
162 //! [`Thread`]: ../../std/thread/struct.Thread.html
163 //! [`park()`]: ../../std/thread/fn.park.html
164 //! [`unpark()`]: ../../std/thread/struct.Thread.html#method.unpark
165 //! [`thread::park_timeout()`]: ../../std/thread/fn.park_timeout.html
166 //! [`Cell`]: ../cell/struct.Cell.html
167 //! [`RefCell`]: ../cell/struct.RefCell.html
168 //! [`thread_local!`]: ../macro.thread_local.html
169 //! [`with`]: struct.LocalKey.html#method.with
171 #![stable(feature = "rust1", since = "1.0.0")]
174 use cell::UnsafeCell;
175 use ffi::{CStr, CString};
181 use sync::{Mutex, Condvar, Arc};
182 use sys::thread as imp;
183 use sys_common::mutex;
184 use sys_common::thread_info;
185 use sys_common::util;
186 use sys_common::{AsInner, IntoInner};
189 ////////////////////////////////////////////////////////////////////////////////
190 // Thread-local storage
191 ////////////////////////////////////////////////////////////////////////////////
193 #[macro_use] mod local;
195 #[stable(feature = "rust1", since = "1.0.0")]
196 pub use self::local::{LocalKey, LocalKeyState};
198 // The types used by the thread_local! macro to access TLS keys. Note that there
199 // are two types, the "OS" type and the "fast" type. The OS thread local key
200 // type is accessed via platform-specific API calls and is slow, while the fast
201 // key type is accessed via code generated via LLVM, where TLS keys are set up
202 // by the elf linker. Note that the OS TLS type is always available: on macOS
203 // the standard library is compiled with support for older platform versions
204 // where fast TLS was not available; end-user code is compiled with fast TLS
205 // where available, but both are needed.
207 #[unstable(feature = "libstd_thread_internals", issue = "0")]
208 #[cfg(target_thread_local)]
209 #[doc(hidden)] pub use sys::fast_thread_local::Key as __FastLocalKeyInner;
210 #[unstable(feature = "libstd_thread_internals", issue = "0")]
211 #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner;
213 ////////////////////////////////////////////////////////////////////////////////
215 ////////////////////////////////////////////////////////////////////////////////
217 /// Thread configuration. Provides detailed control over the properties
218 /// and behavior of new threads.
225 /// let builder = thread::Builder::new();
227 /// let handler = builder.spawn(|| {
231 /// handler.join().unwrap();
233 #[stable(feature = "rust1", since = "1.0.0")]
236 // A name for the thread-to-be, for identification in panic messages
237 name: Option<String>,
238 // The size of the stack for the spawned thread in bytes
239 stack_size: Option<usize>,
243 /// Generates the base configuration for spawning a thread, from which
244 /// configuration methods can be chained.
251 /// let builder = thread::Builder::new()
252 /// .name("foo".into())
255 /// let handler = builder.spawn(|| {
259 /// handler.join().unwrap();
261 #[stable(feature = "rust1", since = "1.0.0")]
262 pub fn new() -> Builder {
269 /// Names the thread-to-be. Currently the name is used for identification
270 /// only in panic messages.
277 /// let builder = thread::Builder::new()
278 /// .name("foo".into());
280 /// let handler = builder.spawn(|| {
281 /// assert_eq!(thread::current().name(), Some("foo"))
284 /// handler.join().unwrap();
286 #[stable(feature = "rust1", since = "1.0.0")]
287 pub fn name(mut self, name: String) -> Builder {
288 self.name = Some(name);
292 /// Sets the size of the stack (in bytes) for the new thread.
294 /// The actual stack size may be greater than this value if
295 /// the platform specifies minimal stack size.
302 /// let builder = thread::Builder::new().stack_size(32 * 1024);
304 #[stable(feature = "rust1", since = "1.0.0")]
305 pub fn stack_size(mut self, size: usize) -> Builder {
306 self.stack_size = Some(size);
310 /// Spawns a new thread, and returns a join handle for it.
312 /// The child thread may outlive the parent (unless the parent thread
313 /// is the main thread; the whole process is terminated when the main
314 /// thread finishes). The join handle can be used to block on
315 /// termination of the child thread, including recovering its panics.
319 /// Unlike the [`spawn`] free function, this method yields an
320 /// [`io::Result`] to capture any failure to create the thread at
323 /// [`spawn`]: ../../std/thread/fn.spawn.html
324 /// [`io::Result`]: ../../std/io/type.Result.html
331 /// let builder = thread::Builder::new();
333 /// let handler = builder.spawn(|| {
337 /// handler.join().unwrap();
339 #[stable(feature = "rust1", since = "1.0.0")]
340 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
341 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
343 let Builder { name, stack_size } = self;
345 let stack_size = stack_size.unwrap_or(util::min_stack());
347 let my_thread = Thread::new(name);
348 let their_thread = my_thread.clone();
350 let my_packet : Arc<UnsafeCell<Option<Result<T>>>>
351 = Arc::new(UnsafeCell::new(None));
352 let their_packet = my_packet.clone();
355 if let Some(name) = their_thread.cname() {
356 imp::Thread::set_name(name);
359 thread_info::set(imp::guard::current(), their_thread);
360 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f));
361 *their_packet.get() = Some(try_result);
365 Ok(JoinHandle(JoinInner {
367 Some(imp::Thread::new(stack_size, Box::new(main))?)
370 packet: Packet(my_packet),
375 ////////////////////////////////////////////////////////////////////////////////
377 ////////////////////////////////////////////////////////////////////////////////
379 /// Spawns a new thread, returning a [`JoinHandle`] for it.
381 /// The join handle will implicitly *detach* the child thread upon being
382 /// dropped. In this case, the child thread may outlive the parent (unless
383 /// the parent thread is the main thread; the whole process is terminated when
384 /// the main thread finishes). Additionally, the join handle provides a [`join`]
385 /// method that can be used to join the child thread. If the child thread
386 /// panics, [`join`] will return an [`Err`] containing the argument given to
391 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
392 /// to recover from such errors.
394 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
395 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
396 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
397 /// [`panic`]: ../../std/macro.panic.html
398 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
405 /// let handler = thread::spawn(|| {
409 /// handler.join().unwrap();
411 #[stable(feature = "rust1", since = "1.0.0")]
412 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
413 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
415 Builder::new().spawn(f).unwrap()
418 /// Gets a handle to the thread that invokes it.
422 /// Getting a handle to the current thread with `thread::current()`:
427 /// let handler = thread::Builder::new()
428 /// .name("named thread".into())
430 /// let handle = thread::current();
431 /// assert_eq!(handle.name(), Some("named thread"));
435 /// handler.join().unwrap();
437 #[stable(feature = "rust1", since = "1.0.0")]
438 pub fn current() -> Thread {
439 thread_info::current_thread().expect("use of std::thread::current() is not \
440 possible after the thread's local \
441 data has been destroyed")
444 /// Cooperatively gives up a timeslice to the OS scheduler.
451 /// thread::yield_now();
453 #[stable(feature = "rust1", since = "1.0.0")]
455 imp::Thread::yield_now()
458 /// Determines whether the current thread is unwinding because of panic.
465 /// struct SomeStruct;
467 /// impl Drop for SomeStruct {
468 /// fn drop(&mut self) {
469 /// if thread::panicking() {
470 /// println!("dropped while unwinding");
472 /// println!("dropped while not unwinding");
479 /// let a = SomeStruct;
484 /// let b = SomeStruct;
489 #[stable(feature = "rust1", since = "1.0.0")]
490 pub fn panicking() -> bool {
491 panicking::panicking()
494 /// Puts the current thread to sleep for the specified amount of time.
496 /// The thread may sleep longer than the duration specified due to scheduling
497 /// specifics or platform-dependent functionality.
499 /// # Platform behavior
501 /// On Unix platforms this function will not return early due to a
502 /// signal being received or a spurious wakeup.
509 /// // Let's sleep for 2 seconds:
510 /// thread::sleep_ms(2000);
512 #[stable(feature = "rust1", since = "1.0.0")]
513 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
514 pub fn sleep_ms(ms: u32) {
515 sleep(Duration::from_millis(ms as u64))
518 /// Puts the current thread to sleep for the specified amount of time.
520 /// The thread may sleep longer than the duration specified due to scheduling
521 /// specifics or platform-dependent functionality.
523 /// # Platform behavior
525 /// On Unix platforms this function will not return early due to a
526 /// signal being received or a spurious wakeup. Platforms which do not support
527 /// nanosecond precision for sleeping will have `dur` rounded up to the nearest
528 /// granularity of time they can sleep for.
533 /// use std::{thread, time};
535 /// let ten_millis = time::Duration::from_millis(10);
536 /// let now = time::Instant::now();
538 /// thread::sleep(ten_millis);
540 /// assert!(now.elapsed() >= ten_millis);
542 #[stable(feature = "thread_sleep", since = "1.4.0")]
543 pub fn sleep(dur: Duration) {
544 imp::Thread::sleep(dur)
547 /// Blocks unless or until the current thread's token is made available.
549 /// Every thread is equipped with some basic low-level blocking support, via
550 /// the `park()` function and the [`unpark()`][unpark] method. These can be
551 /// used as a more CPU-efficient implementation of a spinlock.
553 /// [unpark]: struct.Thread.html#method.unpark
555 /// The API is typically used by acquiring a handle to the current thread,
556 /// placing that handle in a shared data structure so that other threads can
557 /// find it, and then parking (in a loop with a check for the token actually
560 /// A call to `park` does not guarantee that the thread will remain parked
561 /// forever, and callers should be prepared for this possibility.
563 /// See the [module documentation][thread] for more detail.
565 /// [thread]: index.html
567 // The implementation currently uses the trivial strategy of a Mutex+Condvar
568 // with wakeup flag, which does not actually allow spurious wakeups. In the
569 // future, this will be implemented in a more efficient way, perhaps along the lines of
570 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
571 // or futuxes, and in either case may allow spurious wakeups.
572 #[stable(feature = "rust1", since = "1.0.0")]
574 let thread = current();
575 let mut guard = thread.inner.lock.lock().unwrap();
577 guard = thread.inner.cvar.wait(guard).unwrap();
582 /// Use [park_timeout].
584 /// Blocks unless or until the current thread's token is made available or
585 /// the specified duration has been reached (may wake spuriously).
587 /// The semantics of this function are equivalent to `park()` except that the
588 /// thread will be blocked for roughly no longer than `ms`. This method
589 /// should not be used for precise timing due to anomalies such as
590 /// preemption or platform differences that may not cause the maximum
591 /// amount of time waited to be precisely `ms` long.
593 /// See the [module documentation][thread] for more detail.
595 /// [thread]: index.html
596 /// [park_timeout]: fn.park_timeout.html
597 #[stable(feature = "rust1", since = "1.0.0")]
598 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
599 pub fn park_timeout_ms(ms: u32) {
600 park_timeout(Duration::from_millis(ms as u64))
603 /// Blocks unless or until the current thread's token is made available or
604 /// the specified duration has been reached (may wake spuriously).
606 /// The semantics of this function are equivalent to `park()` except that the
607 /// thread will be blocked for roughly no longer than `dur`. This method
608 /// should not be used for precise timing due to anomalies such as
609 /// preemption or platform differences that may not cause the maximum
610 /// amount of time waited to be precisely `dur` long.
612 /// See the module doc for more detail.
614 /// # Platform behavior
616 /// Platforms which do not support nanosecond precision for sleeping will have
617 /// `dur` rounded up to the nearest granularity of time they can sleep for.
621 /// Waiting for the complete expiration of the timeout:
624 /// use std::thread::park_timeout;
625 /// use std::time::{Instant, Duration};
627 /// let timeout = Duration::from_secs(2);
628 /// let beginning_park = Instant::now();
629 /// park_timeout(timeout);
631 /// while beginning_park.elapsed() < timeout {
632 /// println!("restarting park_timeout after {:?}", beginning_park.elapsed());
633 /// let timeout = timeout - beginning_park.elapsed();
634 /// park_timeout(timeout);
637 #[stable(feature = "park_timeout", since = "1.4.0")]
638 pub fn park_timeout(dur: Duration) {
639 let thread = current();
640 let mut guard = thread.inner.lock.lock().unwrap();
642 let (g, _) = thread.inner.cvar.wait_timeout(guard, dur).unwrap();
648 ////////////////////////////////////////////////////////////////////////////////
650 ////////////////////////////////////////////////////////////////////////////////
652 /// A unique identifier for a running thread.
654 /// A `ThreadId` is an opaque object that has a unique value for each thread
655 /// that creates one. `ThreadId`s do not correspond to a thread's system-
656 /// designated identifier.
661 /// #![feature(thread_id)]
665 /// let handler = thread::Builder::new()
667 /// let thread = thread::current();
668 /// let thread_id = thread.id();
672 /// handler.join().unwrap();
674 #[unstable(feature = "thread_id", issue = "21507")]
675 #[derive(Eq, PartialEq, Copy, Clone)]
676 pub struct ThreadId(u64);
679 // Generate a new unique thread ID.
680 fn new() -> ThreadId {
681 static GUARD: mutex::Mutex = mutex::Mutex::new();
682 static mut COUNTER: u64 = 0;
687 // If we somehow use up all our bits, panic so that we're not
688 // covering up subtle bugs of IDs being reused.
689 if COUNTER == ::u64::MAX {
691 panic!("failed to generate unique thread ID: bitspace exhausted");
704 #[unstable(feature = "thread_id", issue = "21507")]
705 impl fmt::Debug for ThreadId {
706 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
707 f.pad("ThreadId { .. }")
711 ////////////////////////////////////////////////////////////////////////////////
713 ////////////////////////////////////////////////////////////////////////////////
715 /// The internal representation of a `Thread` handle
717 name: Option<CString>, // Guaranteed to be UTF-8
719 lock: Mutex<bool>, // true when there is a buffered unpark
724 #[stable(feature = "rust1", since = "1.0.0")]
725 /// A handle to a thread.
732 /// let handler = thread::Builder::new()
733 /// .name("foo".into())
735 /// let thread = thread::current();
736 /// println!("thread name: {}", thread.name().unwrap());
740 /// handler.join().unwrap();
747 // Used only internally to construct a thread object without spawning
748 fn new(name: Option<String>) -> Thread {
749 let cname = name.map(|n| {
750 CString::new(n).expect("thread name may not contain interior null bytes")
753 inner: Arc::new(Inner {
756 lock: Mutex::new(false),
757 cvar: Condvar::new(),
762 /// Atomically makes the handle's token available if it is not already.
764 /// See the module doc for more detail.
771 /// let handler = thread::Builder::new()
773 /// let thread = thread::current();
778 /// handler.join().unwrap();
780 #[stable(feature = "rust1", since = "1.0.0")]
781 pub fn unpark(&self) {
782 let mut guard = self.inner.lock.lock().unwrap();
785 self.inner.cvar.notify_one();
789 /// Gets the thread's unique identifier.
794 /// #![feature(thread_id)]
798 /// let handler = thread::Builder::new()
800 /// let thread = thread::current();
801 /// println!("thread id: {:?}", thread.id());
805 /// handler.join().unwrap();
807 #[unstable(feature = "thread_id", issue = "21507")]
808 pub fn id(&self) -> ThreadId {
812 /// Gets the thread's name.
816 /// Threads by default have no name specified:
821 /// let builder = thread::Builder::new();
823 /// let handler = builder.spawn(|| {
824 /// assert!(thread::current().name().is_none());
827 /// handler.join().unwrap();
830 /// Thread with a specified name:
835 /// let builder = thread::Builder::new()
836 /// .name("foo".into());
838 /// let handler = builder.spawn(|| {
839 /// assert_eq!(thread::current().name(), Some("foo"))
842 /// handler.join().unwrap();
844 #[stable(feature = "rust1", since = "1.0.0")]
845 pub fn name(&self) -> Option<&str> {
846 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } )
849 fn cname(&self) -> Option<&CStr> {
850 self.inner.name.as_ref().map(|s| &**s)
854 #[stable(feature = "rust1", since = "1.0.0")]
855 impl fmt::Debug for Thread {
856 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
857 fmt::Debug::fmt(&self.name(), f)
861 // a hack to get around privacy restrictions
862 impl thread_info::NewThread for Thread {
863 fn new(name: Option<String>) -> Thread { Thread::new(name) }
866 ////////////////////////////////////////////////////////////////////////////////
868 ////////////////////////////////////////////////////////////////////////////////
870 /// Indicates the manner in which a thread exited.
872 /// A thread that completes without panicking is considered to exit successfully.
873 #[stable(feature = "rust1", since = "1.0.0")]
874 pub type Result<T> = ::result::Result<T, Box<Any + Send + 'static>>;
876 // This packet is used to communicate the return value between the child thread
877 // and the parent thread. Memory is shared through the `Arc` within and there's
878 // no need for a mutex here because synchronization happens with `join()` (the
879 // parent thread never reads this packet until the child has exited).
881 // This packet itself is then stored into a `JoinInner` which in turns is placed
882 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
883 // manually worry about impls like Send and Sync. The type `T` should
884 // already always be Send (otherwise the thread could not have been created) and
885 // this type is inherently Sync because no methods take &self. Regardless,
886 // however, we add inheriting impls for Send/Sync to this type to ensure it's
887 // Send/Sync and that future modifications will still appropriately classify it.
888 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
890 unsafe impl<T: Send> Send for Packet<T> {}
891 unsafe impl<T: Sync> Sync for Packet<T> {}
893 /// Inner representation for JoinHandle
894 struct JoinInner<T> {
895 native: Option<imp::Thread>,
900 impl<T> JoinInner<T> {
901 fn join(&mut self) -> Result<T> {
902 self.native.take().unwrap().join();
904 (*self.packet.0.get()).take().unwrap()
909 /// An owned permission to join on a thread (block on its termination).
911 /// A `JoinHandle` *detaches* the child thread when it is dropped.
913 /// Due to platform restrictions, it is not possible to [`Clone`] this
914 /// handle: the ability to join a child thread is a uniquely-owned
917 /// This `struct` is created by the [`thread::spawn`] function and the
918 /// [`thread::Builder::spawn`] method.
922 /// Creation from [`thread::spawn`]:
927 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
928 /// // some work here
932 /// Creation from [`thread::Builder::spawn`]:
937 /// let builder = thread::Builder::new();
939 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
940 /// // some work here
944 /// [`Clone`]: ../../std/clone/trait.Clone.html
945 /// [`thread::spawn`]: fn.spawn.html
946 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
947 #[stable(feature = "rust1", since = "1.0.0")]
948 pub struct JoinHandle<T>(JoinInner<T>);
950 impl<T> JoinHandle<T> {
951 /// Extracts a handle to the underlying thread.
956 /// #![feature(thread_id)]
960 /// let builder = thread::Builder::new();
962 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
963 /// // some work here
966 /// let thread = join_handle.thread();
967 /// println!("thread id: {:?}", thread.id());
969 #[stable(feature = "rust1", since = "1.0.0")]
970 pub fn thread(&self) -> &Thread {
974 /// Waits for the associated thread to finish.
976 /// If the child thread panics, [`Err`] is returned with the parameter given
979 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
980 /// [`panic`]: ../../std/macro.panic.html
987 /// let builder = thread::Builder::new();
989 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
990 /// // some work here
992 /// join_handle.join().expect("Couldn't join on the associated thread");
994 #[stable(feature = "rust1", since = "1.0.0")]
995 pub fn join(mut self) -> Result<T> {
1000 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
1001 fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() }
1004 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1005 fn into_inner(self) -> imp::Thread { self.0.native.unwrap() }
1008 #[stable(feature = "std_debug", since = "1.16.0")]
1009 impl<T> fmt::Debug for JoinHandle<T> {
1010 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1011 f.pad("JoinHandle { .. }")
1015 fn _assert_sync_and_send() {
1016 fn _assert_both<T: Send + Sync>() {}
1017 _assert_both::<JoinHandle<()>>();
1018 _assert_both::<Thread>();
1021 ////////////////////////////////////////////////////////////////////////////////
1023 ////////////////////////////////////////////////////////////////////////////////
1025 #[cfg(all(test, not(target_os = "emscripten")))]
1028 use sync::mpsc::{channel, Sender};
1030 use super::{Builder};
1035 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1036 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1039 fn test_unnamed_thread() {
1040 thread::spawn(move|| {
1041 assert!(thread::current().name().is_none());
1042 }).join().ok().unwrap();
1046 fn test_named_thread() {
1047 Builder::new().name("ada lovelace".to_string()).spawn(move|| {
1048 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1049 }).unwrap().join().unwrap();
1054 fn test_invalid_named_thread() {
1055 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1059 fn test_run_basic() {
1060 let (tx, rx) = channel();
1061 thread::spawn(move|| {
1062 tx.send(()).unwrap();
1068 fn test_join_panic() {
1069 match thread::spawn(move|| {
1072 result::Result::Err(_) => (),
1073 result::Result::Ok(()) => panic!()
1078 fn test_spawn_sched() {
1079 let (tx, rx) = channel();
1081 fn f(i: i32, tx: Sender<()>) {
1082 let tx = tx.clone();
1083 thread::spawn(move|| {
1085 tx.send(()).unwrap();
1097 fn test_spawn_sched_childs_on_default_sched() {
1098 let (tx, rx) = channel();
1100 thread::spawn(move|| {
1101 thread::spawn(move|| {
1102 tx.send(()).unwrap();
1109 fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<Fn() + Send>) {
1110 let (tx, rx) = channel();
1112 let x: Box<_> = box 1;
1113 let x_in_parent = (&*x) as *const i32 as usize;
1115 spawnfn(Box::new(move|| {
1116 let x_in_child = (&*x) as *const i32 as usize;
1117 tx.send(x_in_child).unwrap();
1120 let x_in_child = rx.recv().unwrap();
1121 assert_eq!(x_in_parent, x_in_child);
1125 fn test_avoid_copying_the_body_spawn() {
1126 avoid_copying_the_body(|v| {
1127 thread::spawn(move || v());
1132 fn test_avoid_copying_the_body_thread_spawn() {
1133 avoid_copying_the_body(|f| {
1134 thread::spawn(move|| {
1141 fn test_avoid_copying_the_body_join() {
1142 avoid_copying_the_body(|f| {
1143 let _ = thread::spawn(move|| {
1150 fn test_child_doesnt_ref_parent() {
1151 // If the child refcounts the parent thread, this will stack overflow when
1152 // climbing the thread tree to dereference each ancestor. (See #1789)
1153 // (well, it would if the constant were 8000+ - I lowered it to be more
1154 // valgrind-friendly. try this at home, instead..!)
1155 const GENERATIONS: u32 = 16;
1156 fn child_no(x: u32) -> Box<Fn() + Send> {
1157 return Box::new(move|| {
1158 if x < GENERATIONS {
1159 thread::spawn(move|| child_no(x+1)());
1163 thread::spawn(|| child_no(0)());
1167 fn test_simple_newsched_spawn() {
1168 thread::spawn(move || {});
1172 fn test_try_panic_message_static_str() {
1173 match thread::spawn(move|| {
1174 panic!("static string");
1177 type T = &'static str;
1178 assert!(e.is::<T>());
1179 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1186 fn test_try_panic_message_owned_str() {
1187 match thread::spawn(move|| {
1188 panic!("owned string".to_string());
1192 assert!(e.is::<T>());
1193 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1200 fn test_try_panic_message_any() {
1201 match thread::spawn(move|| {
1202 panic!(box 413u16 as Box<Any + Send>);
1205 type T = Box<Any + Send>;
1206 assert!(e.is::<T>());
1207 let any = e.downcast::<T>().unwrap();
1208 assert!(any.is::<u16>());
1209 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1216 fn test_try_panic_message_unit_struct() {
1219 match thread::spawn(move|| {
1222 Err(ref e) if e.is::<Juju>() => {}
1223 Err(_) | Ok(()) => panic!()
1228 fn test_park_timeout_unpark_before() {
1230 thread::current().unpark();
1231 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1236 fn test_park_timeout_unpark_not_called() {
1238 thread::park_timeout(Duration::from_millis(10));
1243 fn test_park_timeout_unpark_called_other_thread() {
1245 let th = thread::current();
1247 let _guard = thread::spawn(move || {
1248 super::sleep(Duration::from_millis(50));
1252 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1257 fn sleep_ms_smoke() {
1258 thread::sleep(Duration::from_millis(2));
1262 fn test_thread_id_equal() {
1263 assert!(thread::current().id() == thread::current().id());
1267 fn test_thread_id_not_equal() {
1268 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1269 assert!(thread::current().id() != spawned_id);
1272 // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due
1273 // to the test harness apparently interfering with stderr configuration.