/
task.rs
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/
task.rs
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// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Task creation
//!
//! An executing Rust program consists of a collection of tasks, each
//! with their own stack and local state.
//!
//! Tasks generally have their memory *isolated* from each other by
//! virtue of Rust's owned types (which of course may only be owned by
//! a single task at a time). Communication between tasks is primarily
//! done through [channels](../../std/comm/index.html), Rust's
//! message-passing types, though [other forms of task
//! synchronization](../../std/sync/index.html) are often employed to
//! achieve particular performance goals. In particular, types that
//! are guaranteed to be threadsafe are easily shared between threads
//! using the atomically-reference-counted container,
//! [`Arc`](../../std/sync/struct.Arc.html).
//!
//! Fatal logic errors in Rust cause *task panic*, during which
//! a task will unwind the stack, running destructors and freeing
//! owned resources. Task panic is unrecoverable from within
//! the panicking task (i.e. there is no 'try/catch' in Rust), but
//! panic may optionally be detected from a different task. If
//! the main task panics the application will exit with a non-zero
//! exit code.
//!
//! ## Example
//!
//! ```rust
//! spawn(proc() {
//! println!("Hello, World!");
//! })
//! ```
#![unstable = "The task spawning model will be changed as part of runtime reform, and the module \
will likely be renamed from `task` to `thread`."]
use any::Any;
use comm::channel;
use io::{Writer, stdio};
use kinds::{Send, marker};
use option::{None, Some, Option};
use boxed::Box;
use result::Result;
use rustrt::local::Local;
use rustrt::task;
use rustrt::task::Task;
use str::{Str, SendStr, IntoMaybeOwned};
use string::{String, ToString};
use sync::Future;
/// The task builder type.
///
/// Provides detailed control over the properties and behavior of new tasks.
// NB: Builders are designed to be single-use because they do stateful
// things that get weird when reusing - e.g. if you create a result future
// it only applies to a single task, so then you have to maintain Some
// potentially tricky state to ensure that everything behaves correctly
// when you try to reuse the builder to spawn a new task. We'll just
// sidestep that whole issue by making builders uncopyable and making
// the run function move them in.
pub struct TaskBuilder {
// A name for the task-to-be, for identification in panic messages
name: Option<SendStr>,
// The size of the stack for the spawned task
stack_size: Option<uint>,
// Task-local stdout
stdout: Option<Box<Writer + Send>>,
// Task-local stderr
stderr: Option<Box<Writer + Send>>,
// Optionally wrap the eventual task body
gen_body: Option<proc(v: proc():Send):Send -> proc():Send>,
nocopy: marker::NoCopy,
}
impl TaskBuilder {
/// Generate the base configuration for spawning a task, off of which more
/// configuration methods can be chained.
pub fn new() -> TaskBuilder {
TaskBuilder {
name: None,
stack_size: None,
stdout: None,
stderr: None,
gen_body: None,
nocopy: marker::NoCopy,
}
}
}
impl TaskBuilder {
/// Name the task-to-be. Currently the name is used for identification
/// only in panic messages.
#[unstable = "IntoMaybeOwned will probably change."]
pub fn named<T: IntoMaybeOwned<'static>>(mut self, name: T) -> TaskBuilder {
self.name = Some(name.into_maybe_owned());
self
}
/// Set the size of the stack for the new task.
pub fn stack_size(mut self, size: uint) -> TaskBuilder {
self.stack_size = Some(size);
self
}
/// Redirect task-local stdout.
#[experimental = "May not want to make stdio overridable here."]
pub fn stdout(mut self, stdout: Box<Writer + Send>) -> TaskBuilder {
self.stdout = Some(stdout);
self
}
/// Redirect task-local stderr.
#[experimental = "May not want to make stdio overridable here."]
pub fn stderr(mut self, stderr: Box<Writer + Send>) -> TaskBuilder {
self.stderr = Some(stderr);
self
}
// Where spawning actually happens (whether yielding a future or not)
fn spawn_internal(self, f: proc():Send,
on_exit: Option<proc(Result<(), Box<Any + Send>>):Send>) {
let TaskBuilder {
name, stack_size, stdout, stderr, mut gen_body, nocopy: _
} = self;
let f = match gen_body.take() {
Some(gen) => gen(f),
None => f
};
let opts = task::TaskOpts {
on_exit: on_exit,
name: name,
stack_size: stack_size,
};
if stdout.is_some() || stderr.is_some() {
Task::spawn(opts, proc() {
let _ = stdout.map(stdio::set_stdout);
let _ = stderr.map(stdio::set_stderr);
f();
})
} else {
Task::spawn(opts, f)
}
}
/// Creates and executes a new child task.
///
/// Sets up a new task with its own call stack and schedules it to run
/// the provided proc. The task has the properties and behavior
/// specified by the `TaskBuilder`.
pub fn spawn(self, f: proc():Send) {
self.spawn_internal(f, None)
}
/// Execute a proc in a newly-spawned task and return a future representing
/// the task's result. The task has the properties and behavior
/// specified by the `TaskBuilder`.
///
/// Taking the value of the future will block until the child task
/// terminates.
///
/// # Return value
///
/// If the child task executes successfully (without panicking) then the
/// future returns `result::Ok` containing the value returned by the
/// function. If the child task panics then the future returns `result::Err`
/// containing the argument to `panic!(...)` as an `Any` trait object.
#[experimental = "Futures are experimental."]
pub fn try_future<T:Send>(self, f: proc():Send -> T)
-> Future<Result<T, Box<Any + Send>>> {
// currently, the on_exit proc provided by librustrt only works for unit
// results, so we use an additional side-channel to communicate the
// result.
let (tx_done, rx_done) = channel(); // signal that task has exited
let (tx_retv, rx_retv) = channel(); // return value from task
let on_exit = proc(res) { let _ = tx_done.send_opt(res); };
self.spawn_internal(proc() { let _ = tx_retv.send_opt(f()); },
Some(on_exit));
Future::from_fn(proc() {
rx_done.recv().map(|_| rx_retv.recv())
})
}
/// Execute a function in a newly-spawnedtask and block until the task
/// completes or panics. Equivalent to `.try_future(f).unwrap()`.
#[unstable = "Error type may change."]
pub fn try<T:Send>(self, f: proc():Send -> T) -> Result<T, Box<Any + Send>> {
self.try_future(f).unwrap()
}
}
/* Convenience functions */
/// Creates and executes a new child task
///
/// Sets up a new task with its own call stack and schedules it to run
/// the provided unique closure.
///
/// This function is equivalent to `TaskBuilder::new().spawn(f)`.
pub fn spawn(f: proc(): Send) {
TaskBuilder::new().spawn(f)
}
/// Execute a function in a newly-spawned task and return either the return
/// value of the function or an error if the task panicked.
///
/// This is equivalent to `TaskBuilder::new().try`.
#[unstable = "Error type may change."]
pub fn try<T: Send>(f: proc(): Send -> T) -> Result<T, Box<Any + Send>> {
TaskBuilder::new().try(f)
}
/// Execute a function in another task and return a future representing the
/// task's result.
///
/// This is equivalent to `TaskBuilder::new().try_future`.
#[experimental = "Futures are experimental."]
pub fn try_future<T:Send>(f: proc():Send -> T) -> Future<Result<T, Box<Any + Send>>> {
TaskBuilder::new().try_future(f)
}
/* Lifecycle functions */
/// Read the name of the current task.
#[stable]
pub fn name() -> Option<String> {
use rustrt::task::Task;
let task = Local::borrow(None::<Task>);
match task.name {
Some(ref name) => Some(name.as_slice().to_string()),
None => None
}
}
/// Yield control to the task scheduler.
#[unstable = "Name will change."]
pub fn deschedule() {
use rustrt::task::Task;
Task::yield_now();
}
/// True if the running task is currently panicking (e.g. will return `true` inside a
/// destructor that is run while unwinding the stack after a call to `panic!()`).
#[unstable = "May move to a different module."]
pub fn failing() -> bool {
use rustrt::task::Task;
Local::borrow(None::<Task>).unwinder.unwinding()
}
#[cfg(test)]
mod test {
use any::{Any, AnyRefExt};
use boxed::BoxAny;
use result;
use result::{Ok, Err};
use string::String;
use std::io::{ChanReader, ChanWriter};
use prelude::*;
use super::*;
// !!! These tests are dangerous. If something is buggy, they will hang, !!!
// !!! instead of exiting cleanly. This might wedge the buildbots. !!!
#[test]
fn test_unnamed_task() {
try(proc() {
assert!(name().is_none());
}).map_err(|_| ()).unwrap();
}
#[test]
fn test_owned_named_task() {
TaskBuilder::new().named("ada lovelace".to_string()).try(proc() {
assert!(name().unwrap() == "ada lovelace".to_string());
}).map_err(|_| ()).unwrap();
}
#[test]
fn test_static_named_task() {
TaskBuilder::new().named("ada lovelace").try(proc() {
assert!(name().unwrap() == "ada lovelace".to_string());
}).map_err(|_| ()).unwrap();
}
#[test]
fn test_send_named_task() {
TaskBuilder::new().named("ada lovelace".into_maybe_owned()).try(proc() {
assert!(name().unwrap() == "ada lovelace".to_string());
}).map_err(|_| ()).unwrap();
}
#[test]
fn test_run_basic() {
let (tx, rx) = channel();
TaskBuilder::new().spawn(proc() {
tx.send(());
});
rx.recv();
}
#[test]
fn test_try_future() {
let result = TaskBuilder::new().try_future(proc() {});
assert!(result.unwrap().is_ok());
let result = TaskBuilder::new().try_future(proc() -> () {
panic!();
});
assert!(result.unwrap().is_err());
}
#[test]
fn test_try_success() {
match try(proc() {
"Success!".to_string()
}).as_ref().map(|s| s.as_slice()) {
result::Ok("Success!") => (),
_ => panic!()
}
}
#[test]
fn test_try_panic() {
match try(proc() {
panic!()
}) {
result::Err(_) => (),
result::Ok(()) => panic!()
}
}
#[test]
fn test_spawn_sched() {
use clone::Clone;
let (tx, rx) = channel();
fn f(i: int, tx: Sender<()>) {
let tx = tx.clone();
spawn(proc() {
if i == 0 {
tx.send(());
} else {
f(i - 1, tx);
}
});
}
f(10, tx);
rx.recv();
}
#[test]
fn test_spawn_sched_childs_on_default_sched() {
let (tx, rx) = channel();
spawn(proc() {
spawn(proc() {
tx.send(());
});
});
rx.recv();
}
fn avoid_copying_the_body(spawnfn: |v: proc():Send|) {
let (tx, rx) = channel::<uint>();
let x = box 1;
let x_in_parent = (&*x) as *const int as uint;
spawnfn(proc() {
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(spawn);
}
#[test]
fn test_avoid_copying_the_body_task_spawn() {
avoid_copying_the_body(|f| {
let builder = TaskBuilder::new();
builder.spawn(proc() {
f();
});
})
}
#[test]
fn test_avoid_copying_the_body_try() {
avoid_copying_the_body(|f| {
let _ = try(proc() {
f()
});
})
}
#[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) -> proc(): Send {
return proc() {
if x < GENERATIONS {
TaskBuilder::new().spawn(child_no(x+1));
}
}
}
TaskBuilder::new().spawn(child_no(0));
}
#[test]
fn test_simple_newsched_spawn() {
spawn(proc()())
}
#[test]
fn test_try_panic_message_static_str() {
match try(proc() {
panic!("static string");
}) {
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 try(proc() {
panic!("owned string".to_string());
}) {
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 try(proc() {
panic!(box 413u16 as Box<Any + Send>);
}) {
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 try(proc() {
panic!(Juju)
}) {
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 = TaskBuilder::new().stdout(box stdout as Box<Writer + Send>)
.try(proc() {
print!("Hello, world!");
});
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.
}
#[test]
fn task_abort_no_kill_runtime() {
use std::io::timer;
use time::Duration;
use mem;
let tb = TaskBuilder::new();
let rx = tb.try_future(proc() {});
mem::drop(rx);
timer::sleep(Duration::milliseconds(1000));
}