667 lines
21 KiB
Rust
667 lines
21 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Native threads
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//!
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//! ## The threading model
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//!
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//! An executing Rust program consists of a collection of native OS threads,
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//! each with their own stack and local state.
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//!
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//! Communication between threads can be done through
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//! [channels](../../std/comm/index.html), Rust's message-passing
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//! types, along with [other forms of thread
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//! synchronization](../../std/sync/index.html) and shared-memory data
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//! structures. In particular, types that are guaranteed to be
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//! threadsafe are easily shared between threads using the
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//! atomically-reference-counted container,
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//! [`Arc`](../../std/sync/struct.Arc.html).
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//!
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//! Fatal logic errors in Rust cause *thread panic*, during which
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//! a thread will unwind the stack, running destructors and freeing
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//! owned resources. Thread panic is unrecoverable from within
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//! the panicking thread (i.e. there is no 'try/catch' in Rust), but
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//! panic may optionally be detected from a different thread. If
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//! the main thread panics the application will exit with a non-zero
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//! exit code.
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//!
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//! When the main thread of a Rust program terminates, the entire program shuts
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//! down, even if other threads are still running. However, this module provides
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//! convenient facilities for automatically waiting for the termination of a
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//! child thread (i.e., join), described below.
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//!
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//! ## The `Thread` type
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//!
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//! Already-running threads are represented via the `Thread` type, which you can
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//! get in one of two ways:
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//!
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//! * By spawning a new thread, e.g. using the `Thread::spawn` constructor;
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//! * By requesting the current thread, using the `Thread::current` function.
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//!
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//! Threads can be named, and provide some built-in support for low-level
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//! synchronization described below.
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//!
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//! The `Thread::current()` function is available even for threads not spawned
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//! by the APIs of this module.
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//!
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//! ## Spawning a thread
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//!
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//! A new thread can be spawned using the `Thread::spawn` function:
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//!
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//! ```rust
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//! use std::thread::Thread;
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//!
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//! let guard = Thread::spawn(move || {
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//! println!("Hello, World!");
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//! // some computation here
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//! });
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//! let result = guard.join();
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//! ```
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//!
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//! The `spawn` function doesn't return a `Thread` directly; instead, it returns
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//! a *join guard* from which a `Thread` can be extracted. The join guard is an
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//! RAII-style guard that will automatically join the child thread (block until
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//! it terminates) when it is dropped. You can join the child thread in advance
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//! by calling the `join` method on the guard, which will also return the result
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//! produced by the thread.
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//!
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//! If you instead wish to *detach* the child thread, allowing it to outlive its
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//! parent, you can use the `detach` method on the guard,
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//!
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//! A handle to the thread itself is available via the `thread` method on the
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//! join guard.
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//!
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//! ## Configuring threads
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//!
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//! A new thread can be configured before it is spawned via the `Builder` type,
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//! which currently allows you to set the name, stack size, and writers for
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//! `println!` and `panic!` for the child thread:
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//!
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//! ```rust
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//! use std::thread;
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//!
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//! thread::Builder::new().name("child1".to_string()).spawn(move || {
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//! println!("Hello, world!")
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//! }).detach();
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//! ```
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//!
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//! ## Blocking support: park and unpark
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//!
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//! Every thread is equipped with some basic low-level blocking support, via the
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//! `park` and `unpark` functions.
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//!
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//! Conceptually, each `Thread` handle has an associated token, which is
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//! initially not present:
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//!
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//! * The `Thread::park()` function blocks the current thread unless or until
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//! the token is available for its thread handle, at which point It atomically
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//! consumes the token. It may also return *spuriously*, without consuming the
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//! token.
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//!
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//! * The `unpark()` method on a `Thread` atomically makes the token available
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//! if it wasn't already.
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//!
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//! In other words, each `Thread` acts a bit like a semaphore with initial count
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//! 0, except that the semaphore is *saturating* (the count cannot go above 1),
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//! and can return spuriously.
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//!
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//! The API is typically used by acquiring a handle to the current thread,
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//! placing that handle in a shared data structure so that other threads can
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//! find it, and then `park`ing. When some desired condition is met, another
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//! thread calls `unpark` on the handle.
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//!
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//! The motivation for this design is twofold:
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//!
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//! * It avoids the need to allocate mutexes and condvars when building new
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//! synchronization primitives; the threads already provide basic blocking/signaling.
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//!
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//! * It can be implemented highly efficiently on many platforms.
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use any::Any;
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use borrow::IntoCow;
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use boxed::Box;
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use cell::UnsafeCell;
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use clone::Clone;
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use kinds::{Send, Sync};
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use ops::{Drop, FnOnce};
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use option::Option::{mod, Some, None};
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use result::Result::{Err, Ok};
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use sync::{Mutex, Condvar, Arc};
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use str::Str;
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use string::String;
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use rt::{mod, unwind};
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use io::{Writer, stdio};
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use thunk::Thunk;
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use sys::thread as imp;
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use sys_common::{stack, thread_info};
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/// Thread configuation. Provides detailed control over the properties
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/// and behavior of new threads.
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pub struct Builder {
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// A name for the thread-to-be, for identification in panic messages
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name: Option<String>,
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// The size of the stack for the spawned thread
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stack_size: Option<uint>,
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// Thread-local stdout
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stdout: Option<Box<Writer + Send>>,
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// Thread-local stderr
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stderr: Option<Box<Writer + Send>>,
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}
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impl Builder {
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/// Generate the base configuration for spawning a thread, from which
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/// configuration methods can be chained.
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pub fn new() -> Builder {
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Builder {
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name: None,
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stack_size: None,
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stdout: None,
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stderr: None,
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}
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}
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/// Name the thread-to-be. Currently the name is used for identification
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/// only in panic messages.
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pub fn name(mut self, name: String) -> Builder {
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self.name = Some(name);
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self
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}
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/// Deprecated: use `name` instead
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#[deprecated = "use name instead"]
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pub fn named<T: IntoCow<'static, String, str>>(self, name: T) -> Builder {
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self.name(name.into_cow().into_owned())
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}
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/// Set the size of the stack for the new thread.
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pub fn stack_size(mut self, size: uint) -> Builder {
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self.stack_size = Some(size);
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self
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}
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/// Redirect thread-local stdout.
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#[experimental = "Will likely go away after proc removal"]
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pub fn stdout(mut self, stdout: Box<Writer + Send>) -> Builder {
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self.stdout = Some(stdout);
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self
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}
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/// Redirect thread-local stderr.
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#[experimental = "Will likely go away after proc removal"]
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pub fn stderr(mut self, stderr: Box<Writer + Send>) -> Builder {
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self.stderr = Some(stderr);
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self
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}
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/// Spawn a new joinable thread, and return a JoinGuard guard for it.
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///
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/// See `Thead::spawn` and the module doc for more details.
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pub fn spawn<T, F>(self, f: F) -> JoinGuard<T> where
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T: Send, F: FnOnce() -> T, F: Send
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{
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self.spawn_inner(Thunk::new(f))
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}
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fn spawn_inner<T: Send>(self, f: Thunk<(), T>) -> JoinGuard<T> {
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let my_packet = Packet(Arc::new(UnsafeCell::new(None)));
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let their_packet = Packet(my_packet.0.clone());
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let Builder { name, stack_size, stdout, stderr } = self;
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let stack_size = stack_size.unwrap_or(rt::min_stack());
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let my_thread = Thread::new(name);
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let their_thread = my_thread.clone();
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// Spawning a new OS thread guarantees that __morestack will never get
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// triggered, but we must manually set up the actual stack bounds once
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// this function starts executing. This raises the lower limit by a bit
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// because by the time that this function is executing we've already
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// consumed at least a little bit of stack (we don't know the exact byte
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// address at which our stack started).
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let main = move |:| {
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let something_around_the_top_of_the_stack = 1;
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let addr = &something_around_the_top_of_the_stack as *const int;
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let my_stack_top = addr as uint;
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let my_stack_bottom = my_stack_top - stack_size + 1024;
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unsafe {
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stack::record_os_managed_stack_bounds(my_stack_bottom, my_stack_top);
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}
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thread_info::set(
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(my_stack_bottom, my_stack_top),
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unsafe { imp::guard::current() },
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their_thread
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);
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let mut output = None;
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let f: Thunk<(), T> = if stdout.is_some() || stderr.is_some() {
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Thunk::new(move |:| {
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let _ = stdout.map(stdio::set_stdout);
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let _ = stderr.map(stdio::set_stderr);
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f.invoke(())
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})
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} else {
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f
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};
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let try_result = {
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let ptr = &mut output;
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// There are two primary reasons that general try/catch is
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// unsafe. The first is that we do not support nested
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// try/catch. The fact that this is happening in a newly-spawned
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// thread suffices. The second is that unwinding while unwinding
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// is not defined. We take care of that by having an
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// 'unwinding' flag in the thread itself. For these reasons,
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// this unsafety should be ok.
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unsafe {
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unwind::try(move || *ptr = Some(f.invoke(())))
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}
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};
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unsafe {
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*their_packet.0.get() = Some(match (output, try_result) {
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(Some(data), Ok(_)) => Ok(data),
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(None, Err(cause)) => Err(cause),
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_ => unreachable!()
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});
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}
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};
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JoinGuard {
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native: unsafe { imp::create(stack_size, Thunk::new(main)) },
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joined: false,
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packet: my_packet,
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thread: my_thread,
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}
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}
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}
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struct Inner {
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name: Option<String>,
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lock: Mutex<bool>, // true when there is a buffered unpark
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cvar: Condvar,
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}
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unsafe impl Sync for Inner {}
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#[deriving(Clone)]
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/// A handle to a thread.
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pub struct Thread {
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inner: Arc<Inner>,
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}
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unsafe impl Sync for Thread {}
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impl Thread {
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// Used only internally to construct a thread object without spawning
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fn new(name: Option<String>) -> Thread {
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Thread {
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inner: Arc::new(Inner {
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name: name,
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lock: Mutex::new(false),
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cvar: Condvar::new(),
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})
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}
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}
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/// Spawn a new joinable thread, returning a `JoinGuard` for it.
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///
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/// The join guard can be used to explicitly join the child thread (via
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/// `join`), returning `Result<T>`, or it will implicitly join the child
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/// upon being dropped. To detach the child, allowing it to outlive the
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/// current thread, use `detach`. See the module documentation for additional details.
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pub fn spawn<T, F>(f: F) -> JoinGuard<T> where
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T: Send, F: FnOnce() -> T, F: Send
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{
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Builder::new().spawn(f)
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}
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/// Gets a handle to the thread that invokes it.
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pub fn current() -> Thread {
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thread_info::current_thread()
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}
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/// Cooperatively give up a timeslice to the OS scheduler.
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pub fn yield_now() {
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unsafe { imp::yield_now() }
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}
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/// Determines whether the current thread is panicking.
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#[inline]
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pub fn panicking() -> bool {
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unwind::panicking()
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}
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/// Block unless or until the current thread's token is made available (may wake spuriously).
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///
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/// See the module doc for more detail.
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//
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// The implementation currently uses the trivial strategy of a Mutex+Condvar
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// with wakeup flag, which does not actually allow spurious wakeups. In the
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// future, this will be implemented in a more efficient way, perhaps along the lines of
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// http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
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// or futuxes, and in either case may allow spurious wakeups.
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pub fn park() {
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let thread = Thread::current();
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let mut guard = thread.inner.lock.lock().unwrap();
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while !*guard {
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guard = thread.inner.cvar.wait(guard).unwrap();
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}
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*guard = false;
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}
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/// Atomically makes the handle's token available if it is not already.
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///
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/// See the module doc for more detail.
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pub fn unpark(&self) {
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let mut guard = self.inner.lock.lock().unwrap();
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if !*guard {
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*guard = true;
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self.inner.cvar.notify_one();
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}
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}
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/// Get the thread's name.
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pub fn name(&self) -> Option<&str> {
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self.inner.name.as_ref().map(|s| s.as_slice())
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}
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}
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// a hack to get around privacy restrictions
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impl thread_info::NewThread for Thread {
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fn new(name: Option<String>) -> Thread { Thread::new(name) }
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}
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/// Indicates the manner in which a thread exited.
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///
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/// A thread that completes without panicking is considered to exit successfully.
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pub type Result<T> = ::result::Result<T, Box<Any + Send>>;
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struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
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unsafe impl<T:'static+Send> Send for Packet<T> {}
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unsafe impl<T> Sync for Packet<T> {}
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#[must_use]
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/// An RAII-style guard that will block until thread termination when dropped.
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///
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/// The type `T` is the return type for the thread's main function.
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pub struct JoinGuard<T> {
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native: imp::rust_thread,
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thread: Thread,
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joined: bool,
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packet: Packet<T>,
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}
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unsafe impl<T: Send> Sync for JoinGuard<T> {}
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impl<T: Send> JoinGuard<T> {
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/// Extract a handle to the thread this guard will join on.
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pub fn thread(&self) -> &Thread {
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&self.thread
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}
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/// Wait for the associated thread to finish, returning the result of the thread's
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/// calculation.
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///
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/// If the child thread panics, `Err` is returned with the parameter given
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/// to `panic`.
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pub fn join(mut self) -> Result<T> {
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assert!(!self.joined);
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unsafe { imp::join(self.native) };
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self.joined = true;
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unsafe {
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(*self.packet.0.get()).take().unwrap()
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}
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}
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/// Detaches the child thread, allowing it to outlive its parent.
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pub fn detach(mut self) {
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unsafe { imp::detach(self.native) };
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self.joined = true; // avoid joining in the destructor
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}
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}
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#[unsafe_destructor]
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impl<T: Send> Drop for JoinGuard<T> {
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fn drop(&mut self) {
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if !self.joined {
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unsafe { imp::join(self.native) };
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}
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}
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}
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#[cfg(test)]
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mod test {
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use prelude::*;
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use any::{Any, AnyRefExt};
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use boxed::BoxAny;
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use result;
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use std::io::{ChanReader, ChanWriter};
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use thunk::Thunk;
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use super::{Thread, Builder};
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// !!! These tests are dangerous. If something is buggy, they will hang, !!!
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// !!! instead of exiting cleanly. This might wedge the buildbots. !!!
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#[test]
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fn test_unnamed_thread() {
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Thread::spawn(move|| {
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assert!(Thread::current().name().is_none());
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}).join().map_err(|_| ()).unwrap();
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}
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#[test]
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fn test_named_thread() {
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Builder::new().name("ada lovelace".to_string()).spawn(move|| {
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assert!(Thread::current().name().unwrap() == "ada lovelace".to_string());
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}).join().map_err(|_| ()).unwrap();
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}
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#[test]
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fn test_run_basic() {
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let (tx, rx) = channel();
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Thread::spawn(move|| {
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tx.send(());
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}).detach();
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rx.recv();
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}
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#[test]
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fn test_join_success() {
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match Thread::spawn(move|| -> String {
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"Success!".to_string()
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}).join().as_ref().map(|s| s.as_slice()) {
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result::Result::Ok("Success!") => (),
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_ => panic!()
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}
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}
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#[test]
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fn test_join_panic() {
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match Thread::spawn(move|| {
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panic!()
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}).join() {
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result::Result::Err(_) => (),
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result::Result::Ok(()) => panic!()
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}
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}
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#[test]
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fn test_spawn_sched() {
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use clone::Clone;
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let (tx, rx) = channel();
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fn f(i: int, tx: Sender<()>) {
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let tx = tx.clone();
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Thread::spawn(move|| {
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if i == 0 {
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tx.send(());
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} else {
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f(i - 1, tx);
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}
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}).detach();
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}
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f(10, tx);
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rx.recv();
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}
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#[test]
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fn test_spawn_sched_childs_on_default_sched() {
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let (tx, rx) = channel();
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|
Thread::spawn(move|| {
|
|
Thread::spawn(move|| {
|
|
tx.send(());
|
|
}).detach();
|
|
}).detach();
|
|
|
|
rx.recv();
|
|
}
|
|
|
|
fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Thunk) {
|
|
let (tx, rx) = channel::<uint>();
|
|
|
|
let x = box 1;
|
|
let x_in_parent = (&*x) as *const int as uint;
|
|
|
|
spawnfn(Thunk::new(move|| {
|
|
let x_in_child = (&*x) as *const int as uint;
|
|
tx.send(x_in_child);
|
|
}));
|
|
|
|
let x_in_child = rx.recv();
|
|
assert_eq!(x_in_parent, x_in_child);
|
|
}
|
|
|
|
#[test]
|
|
fn test_avoid_copying_the_body_spawn() {
|
|
avoid_copying_the_body(|v| {
|
|
Thread::spawn(move || v.invoke(())).detach();
|
|
});
|
|
}
|
|
|
|
#[test]
|
|
fn test_avoid_copying_the_body_thread_spawn() {
|
|
avoid_copying_the_body(|f| {
|
|
Thread::spawn(move|| {
|
|
f.invoke(());
|
|
}).detach();
|
|
})
|
|
}
|
|
|
|
#[test]
|
|
fn test_avoid_copying_the_body_join() {
|
|
avoid_copying_the_body(|f| {
|
|
let _ = Thread::spawn(move|| {
|
|
f.invoke(())
|
|
}).join();
|
|
})
|
|
}
|
|
|
|
#[test]
|
|
fn test_child_doesnt_ref_parent() {
|
|
// If the child refcounts the parent task, this will stack overflow when
|
|
// climbing the task tree to dereference each ancestor. (See #1789)
|
|
// (well, it would if the constant were 8000+ - I lowered it to be more
|
|
// valgrind-friendly. try this at home, instead..!)
|
|
static GENERATIONS: uint = 16;
|
|
fn child_no(x: uint) -> Thunk {
|
|
return Thunk::new(move|| {
|
|
if x < GENERATIONS {
|
|
Thread::spawn(move|| child_no(x+1).invoke(())).detach();
|
|
}
|
|
});
|
|
}
|
|
Thread::spawn(|| child_no(0).invoke(())).detach();
|
|
}
|
|
|
|
#[test]
|
|
fn test_simple_newsched_spawn() {
|
|
Thread::spawn(move || {}).detach();
|
|
}
|
|
|
|
#[test]
|
|
fn test_try_panic_message_static_str() {
|
|
match Thread::spawn(move|| {
|
|
panic!("static string");
|
|
}).join() {
|
|
Err(e) => {
|
|
type T = &'static str;
|
|
assert!(e.is::<T>());
|
|
assert_eq!(*e.downcast::<T>().unwrap(), "static string");
|
|
}
|
|
Ok(()) => panic!()
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_try_panic_message_owned_str() {
|
|
match Thread::spawn(move|| {
|
|
panic!("owned string".to_string());
|
|
}).join() {
|
|
Err(e) => {
|
|
type T = String;
|
|
assert!(e.is::<T>());
|
|
assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
|
|
}
|
|
Ok(()) => panic!()
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_try_panic_message_any() {
|
|
match Thread::spawn(move|| {
|
|
panic!(box 413u16 as Box<Any + Send>);
|
|
}).join() {
|
|
Err(e) => {
|
|
type T = Box<Any + Send>;
|
|
assert!(e.is::<T>());
|
|
let any = e.downcast::<T>().unwrap();
|
|
assert!(any.is::<u16>());
|
|
assert_eq!(*any.downcast::<u16>().unwrap(), 413u16);
|
|
}
|
|
Ok(()) => panic!()
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_try_panic_message_unit_struct() {
|
|
struct Juju;
|
|
|
|
match Thread::spawn(move|| {
|
|
panic!(Juju)
|
|
}).join() {
|
|
Err(ref e) if e.is::<Juju>() => {}
|
|
Err(_) | Ok(()) => panic!()
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_stdout() {
|
|
let (tx, rx) = channel();
|
|
let mut reader = ChanReader::new(rx);
|
|
let stdout = ChanWriter::new(tx);
|
|
|
|
let r = Builder::new().stdout(box stdout as Box<Writer + Send>).spawn(move|| {
|
|
print!("Hello, world!");
|
|
}).join();
|
|
assert!(r.is_ok());
|
|
|
|
let output = reader.read_to_string().unwrap();
|
|
assert_eq!(output, "Hello, world!".to_string());
|
|
}
|
|
|
|
// NOTE: the corresponding test for stderr is in run-pass/task-stderr, due
|
|
// to the test harness apparently interfering with stderr configuration.
|
|
}
|