1 // Copyright 2013-2014 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.
11 //! Language-level runtime services that should reasonably expected
12 //! to be available 'everywhere'. Local heaps, GC, unwinding,
13 //! local storage, and logging. Even a 'freestanding' Rust would likely want
14 //! to implement this.
22 use iter::{Iterator, Take};
26 use option::{Option, Some, None};
28 use result::{Result, Ok, Err};
31 use rt::local_heap::LocalHeap;
32 use rt::rtio::LocalIo;
33 use rt::unwind::Unwinder;
35 use sync::arc::UnsafeArc;
36 use sync::atomics::{AtomicUint, SeqCst};
37 use task::{TaskResult, TaskOpts};
38 use unstable::finally::Finally;
40 /// The Task struct represents all state associated with a rust
41 /// task. There are at this point two primary "subtypes" of task,
42 /// however instead of using a subtype we just have a "task_type" field
43 /// in the struct. This contains a pointer to another struct that holds
44 /// the type-specific state.
47 pub gc: GarbageCollector,
48 pub storage: LocalStorage,
49 pub unwinder: Unwinder,
52 pub name: Option<SendStr>,
54 pub stdout: Option<~Writer:Send>,
55 pub stderr: Option<~Writer:Send>,
57 imp: Option<~Runtime:Send>,
60 pub struct GarbageCollector;
61 pub struct LocalStorage(pub Option<local_data::Map>);
63 /// A handle to a blocked task. Usually this means having the ~Task pointer by
64 /// ownership, but if the task is killable, a killer can steal it at any time.
65 pub enum BlockedTask {
67 Shared(UnsafeArc<AtomicUint>),
70 pub enum DeathAction {
71 /// Action to be done with the exit code. If set, also makes the task wait
72 /// until all its watched children exit before collecting the status.
73 Execute(proc(TaskResult):Send),
74 /// A channel to send the result of the task on when the task exits
75 SendMessage(Sender<TaskResult>),
78 /// Per-task state related to task death, killing, failure, etc.
80 pub on_exit: Option<DeathAction>,
83 pub struct BlockedTasks {
84 inner: UnsafeArc<AtomicUint>,
88 pub fn new() -> Task {
90 heap: LocalHeap::new(),
92 storage: LocalStorage(None),
93 unwinder: Unwinder::new(),
103 /// Executes the given closure as if it's running inside this task. The task
104 /// is consumed upon entry, and the destroyed task is returned from this
105 /// function in order for the caller to free. This function is guaranteed to
106 /// not unwind because the closure specified is run inside of a `rust_try`
107 /// block. (this is the only try/catch block in the world).
109 /// This function is *not* meant to be abused as a "try/catch" block. This
110 /// is meant to be used at the absolute boundaries of a task's lifetime, and
111 /// only for that purpose.
112 pub fn run(~self, f: ||) -> ~Task {
113 // Need to put ourselves into TLS, but also need access to the unwinder.
114 // Unsafely get a handle to the task so we can continue to use it after
115 // putting it in tls (so we can invoke the unwinder).
116 let handle: *mut Task = unsafe {
117 *cast::transmute::<&~Task, &*mut Task>(&self)
121 // The only try/catch block in the world. Attempt to run the task's
122 // client-specified code and catch any failures.
125 // Run the task main function, then do some cleanup.
127 #[allow(unused_must_use)]
129 let mut task = Local::borrow(None::<Task>);
130 let stderr = task.stderr.take();
131 let stdout = task.stdout.take();
133 match stdout { Some(mut w) => { w.flush(); }, None => {} }
134 match stderr { Some(mut w) => { w.flush(); }, None => {} }
137 // First, flush/destroy the user stdout/logger because these
138 // destructors can run arbitrary code.
141 // First, destroy task-local storage. This may run user dtors.
143 // FIXME #8302: Dear diary. I'm so tired and confused.
144 // There's some interaction in rustc between the box
145 // annihilator and the TLS dtor by which TLS is
146 // accessed from annihilated box dtors *after* TLS is
147 // destroyed. Somehow setting TLS back to null, as the
148 // old runtime did, makes this work, but I don't currently
149 // understand how. I would expect that, if the annihilator
150 // reinvokes TLS while TLS is uninitialized, that
151 // TLS would be reinitialized but never destroyed,
152 // but somehow this works. I have no idea what's going
153 // on but this seems to make things magically work. FML.
155 // (added after initial comment) A possible interaction here is
156 // that the destructors for the objects in TLS themselves invoke
157 // TLS, or possibly some destructors for those objects being
158 // annihilated invoke TLS. Sadly these two operations seemed to
159 // be intertwined, and miraculously work for now...
160 let mut task = Local::borrow(None::<Task>);
162 let &LocalStorage(ref mut optmap) = &mut task.storage;
168 // Destroy remaining boxes. Also may run user dtors.
169 unsafe { cleanup::annihilate(); }
171 // Finally, just in case user dtors printed/logged during TLS
172 // cleanup and annihilation, re-destroy stdout and the logger.
173 // Note that these will have been initialized with a
174 // runtime-provided type which we have control over what the
180 unsafe { (*handle).unwinder.try(try_block); }
182 // Here we must unsafely borrow the task in order to not remove it from
183 // TLS. When collecting failure, we may attempt to send on a channel (or
184 // just run aribitrary code), so we must be sure to still have a local
187 let me: *mut Task = Local::unsafe_borrow();
188 (*me).death.collect_failure((*me).unwinder.result());
190 let mut me: ~Task = Local::take();
195 /// Inserts a runtime object into this task, transferring ownership to the
196 /// task. It is illegal to replace a previous runtime object in this task
197 /// with this argument.
198 pub fn put_runtime(&mut self, ops: ~Runtime:Send) {
199 assert!(self.imp.is_none());
200 self.imp = Some(ops);
203 /// Attempts to extract the runtime as a specific type. If the runtime does
204 /// not have the provided type, then the runtime is not removed. If the
205 /// runtime does have the specified type, then it is removed and returned
206 /// (transfer of ownership).
208 /// It is recommended to only use this method when *absolutely necessary*.
209 /// This function may not be available in the future.
210 pub fn maybe_take_runtime<T: 'static>(&mut self) -> Option<~T> {
211 // This is a terrible, terrible function. The general idea here is to
212 // take the runtime, cast it to ~Any, check if it has the right type,
213 // and then re-cast it back if necessary. The method of doing this is
214 // pretty sketchy and involves shuffling vtables of trait objects
215 // around, but it gets the job done.
217 // FIXME: This function is a serious code smell and should be avoided at
218 // all costs. I have yet to think of a method to avoid this
219 // function, and I would be saddened if more usage of the function
222 let imp = self.imp.take_unwrap();
223 let &(vtable, _): &(uint, uint) = cast::transmute(&imp);
224 match imp.wrap().move::<T>() {
227 let (_, obj): (uint, uint) = cast::transmute(t);
228 let obj: ~Runtime:Send = cast::transmute((vtable, obj));
229 self.put_runtime(obj);
236 /// Spawns a sibling to this task. The newly spawned task is configured with
237 /// the `opts` structure and will run `f` as the body of its code.
238 pub fn spawn_sibling(mut ~self, opts: TaskOpts, f: proc():Send) {
239 let ops = self.imp.take_unwrap();
240 ops.spawn_sibling(self, opts, f)
243 /// Deschedules the current task, invoking `f` `amt` times. It is not
244 /// recommended to use this function directly, but rather communication
245 /// primitives in `std::comm` should be used.
246 pub fn deschedule(mut ~self, amt: uint,
247 f: |BlockedTask| -> Result<(), BlockedTask>) {
248 let ops = self.imp.take_unwrap();
249 ops.deschedule(amt, self, f)
252 /// Wakes up a previously blocked task, optionally specifying whether the
253 /// current task can accept a change in scheduling. This function can only
254 /// be called on tasks that were previously blocked in `deschedule`.
255 pub fn reawaken(mut ~self) {
256 let ops = self.imp.take_unwrap();
260 /// Yields control of this task to another task. This function will
261 /// eventually return, but possibly not immediately. This is used as an
262 /// opportunity to allow other tasks a chance to run.
263 pub fn yield_now(mut ~self) {
264 let ops = self.imp.take_unwrap();
268 /// Similar to `yield_now`, except that this function may immediately return
269 /// without yielding (depending on what the runtime decides to do).
270 pub fn maybe_yield(mut ~self) {
271 let ops = self.imp.take_unwrap();
272 ops.maybe_yield(self);
275 /// Acquires a handle to the I/O factory that this task contains, normally
276 /// stored in the task's runtime. This factory may not always be available,
277 /// which is why the return type is `Option`
278 pub fn local_io<'a>(&'a mut self) -> Option<LocalIo<'a>> {
279 self.imp.get_mut_ref().local_io()
282 /// Returns the stack bounds for this task in (lo, hi) format. The stack
283 /// bounds may not be known for all tasks, so the return value may be
285 pub fn stack_bounds(&self) -> (uint, uint) {
286 self.imp.get_ref().stack_bounds()
289 /// Returns whether it is legal for this task to block the OS thread that it
291 pub fn can_block(&self) -> bool {
292 self.imp.get_ref().can_block()
298 rtdebug!("called drop for a task: {}", self as *mut Task as uint);
299 rtassert!(self.destroyed);
303 impl Iterator<BlockedTask> for BlockedTasks {
304 fn next(&mut self) -> Option<BlockedTask> {
305 Some(Shared(self.inner.clone()))
310 /// Returns Some if the task was successfully woken; None if already killed.
311 pub fn wake(self) -> Option<~Task> {
313 Owned(task) => Some(task),
314 Shared(arc) => unsafe {
315 match (*arc.get()).swap(0, SeqCst) {
317 n => Some(cast::transmute(n)),
323 // This assertion has two flavours because the wake involves an atomic op.
324 // In the faster version, destructors will fail dramatically instead.
325 #[cfg(not(test))] pub fn trash(self) { }
326 #[cfg(test)] pub fn trash(self) { assert!(self.wake().is_none()); }
328 /// Create a blocked task, unless the task was already killed.
329 pub fn block(task: ~Task) -> BlockedTask {
333 /// Converts one blocked task handle to a list of many handles to the same.
334 pub fn make_selectable(self, num_handles: uint) -> Take<BlockedTasks> {
335 let arc = match self {
337 let flag = unsafe { AtomicUint::new(cast::transmute(task)) };
340 Shared(arc) => arc.clone(),
342 BlockedTasks{ inner: arc }.take(num_handles)
345 /// Convert to an unsafe uint value. Useful for storing in a pipe's state
348 pub unsafe fn cast_to_uint(self) -> uint {
351 let blocked_task_ptr: uint = cast::transmute(task);
352 rtassert!(blocked_task_ptr & 0x1 == 0);
356 let blocked_task_ptr: uint = cast::transmute(~arc);
357 rtassert!(blocked_task_ptr & 0x1 == 0);
358 blocked_task_ptr | 0x1
363 /// Convert from an unsafe uint value. Useful for retrieving a pipe's state
366 pub unsafe fn cast_from_uint(blocked_task_ptr: uint) -> BlockedTask {
367 if blocked_task_ptr & 0x1 == 0 {
368 Owned(cast::transmute(blocked_task_ptr))
370 let ptr: ~UnsafeArc<AtomicUint> =
371 cast::transmute(blocked_task_ptr & !1);
378 pub fn new() -> Death {
379 Death { on_exit: None, }
382 /// Collect failure exit codes from children and propagate them to a parent.
383 pub fn collect_failure(&mut self, result: TaskResult) {
384 match self.on_exit.take() {
385 Some(Execute(f)) => f(result),
386 Some(SendMessage(ch)) => { let _ = ch.send_opt(result); }
392 impl Drop for Death {
394 // make this type noncopyable
415 local_data_key!(key: @~str)
416 local_data::set(key, @"data".to_owned());
417 assert!(*local_data::get(key, |k| k.map(|k| *k)).unwrap() == "data".to_owned());
418 local_data_key!(key2: @~str)
419 local_data::set(key2, @"data".to_owned());
420 assert!(*local_data::get(key2, |k| k.map(|k| *k)).unwrap() == "data".to_owned());
425 let result = task::try(proc()());
426 rtdebug!("trying first assert");
427 assert!(result.is_ok());
428 let result = task::try::<()>(proc() fail!());
429 rtdebug!("trying second assert");
430 assert!(result.is_err());
435 use rand::{StdRng, Rng};
436 let mut r = StdRng::new().unwrap();
437 let _ = r.next_u32();
442 info!("here i am. logging in a newsched task");
447 let (tx, rx) = channel();
449 assert!(rx.recv() == 10);
453 fn comm_shared_chan() {
454 let (tx, rx) = channel();
456 assert!(rx.recv() == 10);
462 use option::{Option, Some, None};
465 next: Option<@RefCell<List>>,
468 let a = @RefCell::new(List { next: None });
469 let b = @RefCell::new(List { next: Some(a) });
472 let mut a = a.borrow_mut();
479 fn test_begin_unwind() {
480 use rt::unwind::begin_unwind;
481 begin_unwind("cause", file!(), line!())
484 // Task blocking tests
487 fn block_and_wake() {
488 let task = ~Task::new();
489 let mut task = BlockedTask::block(task).wake().unwrap();
490 task.destroyed = true;