[rust.git] / src / libstd / task / spawn.rs

// 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.

/*!**************************************************************************
 * Spawning & linked failure
 *
 * Several data structures are involved in task management to allow properly
 * propagating failure across linked/supervised tasks.
 *
 * (1) The "taskgroup_arc" is an unsafe::exclusive which contains a hashset of
 *     all tasks that are part of the group. Some tasks are 'members', which
 *     means if they fail, they will kill everybody else in the taskgroup.
 *     Other tasks are 'descendants', which means they will not kill tasks
 *     from this group, but can be killed by failing members.
 *
 *     A new one of these is created each spawn_linked or spawn_supervised.
 *
 * (2) The "taskgroup" is a per-task control structure that tracks a task's
 *     spawn configuration. It contains a reference to its taskgroup_arc, a
 *     reference to its node in the ancestor list (below), and an optionally
 *     configured notification port. These are stored in TLS.
 *
 * (3) The "ancestor_list" is a cons-style list of unsafe::exclusives which
 *     tracks 'generations' of taskgroups -- a group's ancestors are groups
 *     which (directly or transitively) spawn_supervised-ed them. Each task
 *     is recorded in the 'descendants' of each of its ancestor groups.
 *
 *     Spawning a supervised task is O(n) in the number of generations still
 *     alive, and exiting (by success or failure) that task is also O(n).
 *
 * This diagram depicts the references between these data structures:
 *
 *          linked_________________________________
 *        ___/                   _________         \___
 *       /   \                  | group X |        /   \
 *      (  A  ) - - - - - - - > | {A,B} {}|< - - -(  B  )
 *       \___/                  |_________|        \___/
 *      unlinked
 *         |      __ (nil)
 *         |      //|                         The following code causes this:
 *         |__   //   /\         _________
 *        /   \ //    ||        | group Y |     fn taskA() {
 *       (  C  )- - - ||- - - > |{C} {D,E}|         spawn(taskB);
 *        \___/      /  \=====> |_________|         spawn_unlinked(taskC);
 *      supervise   /gen \                          ...
 *         |    __  \ 00 /                      }
 *         |    //|  \__/                       fn taskB() { ... }
 *         |__ //     /\         _________      fn taskC() {
 *        /   \/      ||        | group Z |         spawn_supervised(taskD);
 *       (  D  )- - - ||- - - > | {D} {E} |         ...
 *        \___/      /  \=====> |_________|     }
 *      supervise   /gen \                      fn taskD() {
 *         |    __  \ 01 /                          spawn_supervised(taskE);
 *         |    //|  \__/                           ...
 *         |__ //                _________      }
 *        /   \/                | group W |     fn taskE() { ... }
 *       (  E  )- - - - - - - > | {E}  {} |
 *        \___/                 |_________|
 *
 *        "tcb"               "taskgroup_arc"
 *             "ancestor_list"
 *
 ****************************************************************************/

#[doc(hidden)];

use prelude::*;

use cast::transmute;
use cast;
use cell::Cell;
use container::MutableMap;
use comm::{Chan, GenericChan, oneshot};
use hashmap::{HashSet, HashSetMoveIterator};
use local_data;
use task::{Failure, SingleThreaded};
use task::{Success, TaskOpts, TaskResult};
use task::unkillable;
use uint;
use util;
use unstable::sync::Exclusive;
use rt::in_green_task_context;
use rt::local::Local;
use rt::task::{Task, Sched};
use rt::kill::KillHandle;
use rt::sched::Scheduler;
use rt::uv::uvio::UvEventLoop;
use rt::thread::Thread;
use rt::work_queue::WorkQueue;

#[cfg(test)] use task::default_task_opts;
#[cfg(test)] use comm;
#[cfg(test)] use task;

struct TaskSet(HashSet<KillHandle>);

impl TaskSet {
    #[inline]
    fn new() -> TaskSet {
        TaskSet(HashSet::new())
    }
    #[inline]
    fn insert(&mut self, task: KillHandle) {
        let didnt_overwrite = (**self).insert(task);
        assert!(didnt_overwrite);
    }
    #[inline]
    fn remove(&mut self, task: &KillHandle) {
        let was_present = (**self).remove(task);
        assert!(was_present);
    }
    #[inline]
    fn move_iter(self) -> HashSetMoveIterator<KillHandle> {
        (*self).move_iter()
    }
}

// One of these per group of linked-failure tasks.
struct TaskGroupData {
    // All tasks which might kill this group. When this is empty, the group
    // can be "GC"ed (i.e., its link in the ancestor list can be removed).
    members:     TaskSet,
    // All tasks unidirectionally supervised by (directly or transitively)
    // tasks in this group.
    descendants: TaskSet,
}
type TaskGroupArc = Exclusive<Option<TaskGroupData>>;

type TaskGroupInner<'self> = &'self mut Option<TaskGroupData>;

// A taskgroup is 'dead' when nothing can cause it to fail; only members can.
fn taskgroup_is_dead(tg: &TaskGroupData) -> bool {
    tg.members.is_empty()
}

// A list-like structure by which taskgroups keep track of all ancestor groups
// which may kill them. Needed for tasks to be able to remove themselves from
// ancestor groups upon exit. The list has a node for each "generation", and
// ends either at the root taskgroup (which has no ancestors) or at a
// taskgroup which was spawned-unlinked. Tasks from intermediate generations
// have references to the middle of the list; when intermediate generations
// die, their node in the list will be collected at a descendant's spawn-time.
struct AncestorNode {
    // Since the ancestor list is recursive, we end up with references to
    // exclusives within other exclusives. This is dangerous business (if
    // circular references arise, deadlock and memory leaks are imminent).
    // Hence we assert that this counter monotonically decreases as we
    // approach the tail of the list.
    generation:     uint,
    // Handle to the tasks in the group of the current generation.
    parent_group:   TaskGroupArc,
    // Recursive rest of the list.
    ancestors:      AncestorList,
}

struct AncestorList(Option<Exclusive<AncestorNode>>);

// Accessors for taskgroup arcs and ancestor arcs that wrap the unsafety.
#[inline]
fn access_group<U>(x: &TaskGroupArc, blk: &fn(TaskGroupInner) -> U) -> U {
    unsafe {
        x.with(blk)
    }
}

#[inline]
fn access_ancestors<U>(x: &Exclusive<AncestorNode>,
                       blk: &fn(x: &mut AncestorNode) -> U) -> U {
    unsafe {
        x.with(blk)
    }
}

#[inline] #[cfg(test)]
fn check_generation(younger: uint, older: uint) { assert!(younger > older); }
#[inline] #[cfg(not(test))]
fn check_generation(_younger: uint, _older: uint) { }

#[inline] #[cfg(test)]
fn incr_generation(ancestors: &AncestorList) -> uint {
    ancestors.map_default(0, |arc| access_ancestors(arc, |a| a.generation+1))
}
#[inline] #[cfg(not(test))]
fn incr_generation(_ancestors: &AncestorList) -> uint { 0 }

// Iterates over an ancestor list.
// (1) Runs forward_blk on each ancestral taskgroup in the list
// (2) If forward_blk "break"s, runs optional bail_blk on all ancestral
//     taskgroups that forward_blk already ran on successfully (Note: bail_blk
//     is NOT called on the block that forward_blk broke on!).
// (3) As a bonus, coalesces away all 'dead' taskgroup nodes in the list.
fn each_ancestor(list:        &mut AncestorList,
                 bail_blk:    &fn(TaskGroupInner),
                 forward_blk: &fn(TaskGroupInner) -> bool)
              -> bool {
    // "Kickoff" call - there was no last generation.
    return !coalesce(list, bail_blk, forward_blk, uint::max_value);

    // Recursively iterates, and coalesces afterwards if needed. Returns
    // whether or not unwinding is needed (i.e., !successful iteration).
    fn coalesce(list:            &mut AncestorList,
                bail_blk:        &fn(TaskGroupInner),
                forward_blk:     &fn(TaskGroupInner) -> bool,
                last_generation: uint) -> bool {
        let (coalesce_this, early_break) =
            iterate(list, bail_blk, forward_blk, last_generation);
        // What should our next ancestor end up being?
        if coalesce_this.is_some() {
            // Needed coalesce. Our next ancestor becomes our old
            // ancestor's next ancestor. ("next = old_next->next;")
            *list = coalesce_this.unwrap();
        }
        return early_break;
    }

    // Returns an optional list-to-coalesce and whether unwinding is needed.
    // Option<ancestor_list>:
    //     Whether or not the ancestor taskgroup being iterated over is
    //     dead or not; i.e., it has no more tasks left in it, whether or not
    //     it has descendants. If dead, the caller shall coalesce it away.
    // bool:
    //     True if the supplied block did 'break', here or in any recursive
    //     calls. If so, must call the unwinder on all previous nodes.
    fn iterate(ancestors:       &mut AncestorList,
               bail_blk:        &fn(TaskGroupInner),
               forward_blk:     &fn(TaskGroupInner) -> bool,
               last_generation: uint)
            -> (Option<AncestorList>, bool) {
        // At each step of iteration, three booleans are at play which govern
        // how the iteration should behave.
        // 'nobe_is_dead' - Should the list should be coalesced at this point?
        //                  Largely unrelated to the other two.
        // 'need_unwind'  - Should we run the bail_blk at this point? (i.e.,
        //                  do_continue was false not here, but down the line)
        // 'do_continue'  - Did the forward_blk succeed at this point? (i.e.,
        //                  should we recurse? or should our callers unwind?)

        let forward_blk = Cell::new(forward_blk);

        // The map defaults to None, because if ancestors is None, we're at
        // the end of the list, which doesn't make sense to coalesce.
        do ancestors.map_default((None,false)) |ancestor_arc| {
            // NB: Takes a lock! (this ancestor node)
            do access_ancestors(ancestor_arc) |nobe| {
                // Argh, but we couldn't give it to coalesce() otherwise.
                let forward_blk = forward_blk.take();
                // Check monotonicity
                check_generation(last_generation, nobe.generation);
                /*##########################################################*
                 * Step 1: Look at this ancestor group (call iterator block).
                 *##########################################################*/
                let mut nobe_is_dead = false;
                let do_continue =
                    // NB: Takes a lock! (this ancestor node's parent group)
                    do access_group(&nobe.parent_group) |tg_opt| {
                        // Decide whether this group is dead. Note that the
                        // group being *dead* is disjoint from it *failing*.
                        nobe_is_dead = match *tg_opt {
                            Some(ref tg) => taskgroup_is_dead(tg),
                            None => nobe_is_dead
                        };
                        // Call iterator block. (If the group is dead, it's
                        // safe to skip it. This will leave our KillHandle
                        // hanging around in the group even after it's freed,
                        // but that's ok because, by virtue of the group being
                        // dead, nobody will ever kill-all (for) over it.)
                        if nobe_is_dead { true } else { forward_blk(tg_opt) }
                    };
                /*##########################################################*
                 * Step 2: Recurse on the rest of the list; maybe coalescing.
                 *##########################################################*/
                // 'need_unwind' is only set if blk returned true above, *and*
                // the recursive call early-broke.
                let mut need_unwind = false;
                if do_continue {
                    // NB: Takes many locks! (ancestor nodes & parent groups)
                    need_unwind = coalesce(&mut nobe.ancestors, |tg| bail_blk(tg),
                                           forward_blk, nobe.generation);
                }
                /*##########################################################*
                 * Step 3: Maybe unwind; compute return info for our caller.
                 *##########################################################*/
                if need_unwind && !nobe_is_dead {
                    do access_group(&nobe.parent_group) |tg_opt| {
                        bail_blk(tg_opt)
                    }
                }
                // Decide whether our caller should unwind.
                need_unwind = need_unwind || !do_continue;
                // Tell caller whether or not to coalesce and/or unwind
                if nobe_is_dead {
                    // Swap the list out here; the caller replaces us with it.
                    let rest = util::replace(&mut nobe.ancestors,
                                             AncestorList(None));
                    (Some(rest), need_unwind)
                } else {
                    (None, need_unwind)
                }
            }
        }
    }
}

// One of these per task.
pub struct Taskgroup {
    // List of tasks with whose fates this one's is intertwined.
    tasks:      TaskGroupArc, // 'none' means the group has failed.
    // Lists of tasks who will kill us if they fail, but whom we won't kill.
    ancestors:  AncestorList,
    notifier:   Option<AutoNotify>,
}

impl Drop for Taskgroup {
    // Runs on task exit.
    fn drop(&self) {
        unsafe {
            // FIXME(#4330) Need self by value to get mutability.
            let this: &mut Taskgroup = transmute(self);

            // If we are failing, the whole taskgroup needs to die.
            do RuntimeGlue::with_task_handle_and_failing |me, failing| {
                if failing {
                    for x in this.notifier.mut_iter() {
                        x.failed = true;
                    }
                    // Take everybody down with us. After this point, every
                    // other task in the group will see 'tg' as none, which
                    // indicates the whole taskgroup is failing (and forbids
                    // new spawns from succeeding).
                    let tg = do access_group(&self.tasks) |tg| { tg.take() };
                    // It's safe to send kill signals outside the lock, because
                    // we have a refcount on all kill-handles in the group.
                    kill_taskgroup(tg, me);
                } else {
                    // Remove ourselves from the group(s).
                    do access_group(&self.tasks) |tg| {
                        leave_taskgroup(tg, me, true);
                    }
                }
                // It doesn't matter whether this happens before or after dealing
                // with our own taskgroup, so long as both happen before we die.
                // We remove ourself from every ancestor we can, so no cleanup; no
                // break.
                do each_ancestor(&mut this.ancestors, |_| {}) |ancestor_group| {
                    leave_taskgroup(ancestor_group, me, false);
                    true
                };
            }
        }
    }
}

pub fn Taskgroup(tasks: TaskGroupArc,
       ancestors: AncestorList,
       mut notifier: Option<AutoNotify>) -> Taskgroup {
    for x in notifier.mut_iter() {
        x.failed = false;
    }

    Taskgroup {
        tasks: tasks,
        ancestors: ancestors,
        notifier: notifier
    }
}

struct AutoNotify {
    notify_chan: Chan<TaskResult>,
    failed: bool,
}

impl Drop for AutoNotify {
    fn drop(&self) {
        let result = if self.failed { Failure } else { Success };
        self.notify_chan.send(result);
    }
}

fn AutoNotify(chan: Chan<TaskResult>) -> AutoNotify {
    AutoNotify {
        notify_chan: chan,
        failed: true // Un-set above when taskgroup successfully made.
    }
}

fn enlist_in_taskgroup(state: TaskGroupInner, me: KillHandle,
                           is_member: bool) -> bool {
    let me = Cell::new(me); // :(
    // If 'None', the group was failing. Can't enlist.
    do state.map_mut_default(false) |group| {
        (if is_member {
            &mut group.members
        } else {
            &mut group.descendants
        }).insert(me.take());
        true
    }
}

// NB: Runs in destructor/post-exit context. Can't 'fail'.
fn leave_taskgroup(state: TaskGroupInner, me: &KillHandle, is_member: bool) {
    let me = Cell::new(me); // :(
    // If 'None', already failing and we've already gotten a kill signal.
    do state.map_mut |group| {
        (if is_member {
            &mut group.members
        } else {
            &mut group.descendants
        }).remove(me.take());
    };
}

// NB: Runs in destructor/post-exit context. Can't 'fail'.
fn kill_taskgroup(state: Option<TaskGroupData>, me: &KillHandle) {
    // Might already be None, if somebody is failing simultaneously.
    // That's ok; only one task needs to do the dirty work. (Might also
    // see 'None' if somebody already failed and we got a kill signal.)
    do state.map_move |TaskGroupData { members: members, descendants: descendants }| {
        for sibling in members.move_iter() {
            // Skip self - killing ourself won't do much good.
            if &sibling != me {
                RuntimeGlue::kill_task(sibling);
            }
        }
        for child in descendants.move_iter() {
            assert!(&child != me);
            RuntimeGlue::kill_task(child);
        }
    };
    // (note: multiple tasks may reach this point)
}

// FIXME (#2912): Work around core-vs-coretest function duplication. Can't use
// a proper closure because the #[test]s won't understand. Have to fake it.
fn taskgroup_key() -> local_data::Key<@@mut Taskgroup> {
    unsafe { cast::transmute(-2) }
}

// Transitionary.
struct RuntimeGlue;
impl RuntimeGlue {
    fn kill_task(mut handle: KillHandle) {
        do handle.kill().map_move |killed_task| {
            let killed_task = Cell::new(killed_task);
            do Local::borrow |sched: &mut Scheduler| {
                sched.enqueue_task(killed_task.take());
            }
        };
    }

    fn with_task_handle_and_failing(blk: &fn(&KillHandle, bool)) {
        rtassert!(in_green_task_context());
        unsafe {
            // Can't use safe borrow, because the taskgroup destructor needs to
            // access the scheduler again to send kill signals to other tasks.
            let me: *mut Task = Local::unsafe_borrow();
            blk((*me).death.kill_handle.get_ref(), (*me).unwinder.unwinding)
        }
    }

    fn with_my_taskgroup<U>(blk: &fn(&Taskgroup) -> U) -> U {
        rtassert!(in_green_task_context());
        unsafe {
            // Can't use safe borrow, because creating new hashmaps for the
            // tasksets requires an rng, which needs to borrow the sched.
            let me: *mut Task = Local::unsafe_borrow();
            blk(match (*me).taskgroup {
                None => {
                    // First task in its (unlinked/unsupervised) taskgroup.
                    // Lazily initialize.
                    let mut members = TaskSet::new();
                    let my_handle = (*me).death.kill_handle.get_ref().clone();
                    members.insert(my_handle);
                    let tasks = Exclusive::new(Some(TaskGroupData {
                        members: members,
                        descendants: TaskSet::new(),
                    }));
                    let group = Taskgroup(tasks, AncestorList(None), None);
                    (*me).taskgroup = Some(group);
                    (*me).taskgroup.get_ref()
                }
                Some(ref group) => group,
            })
        }
    }
}

// Returns 'None' in the case where the child's TG should be lazily initialized.
fn gen_child_taskgroup(linked: bool, supervised: bool)
    -> Option<(TaskGroupArc, AncestorList)> {
    if linked || supervised {
        // with_my_taskgroup will lazily initialize the parent's taskgroup if
        // it doesn't yet exist. We don't want to call it in the unlinked case.
        do RuntimeGlue::with_my_taskgroup |spawner_group| {
            let ancestors = AncestorList(spawner_group.ancestors.map(|x| x.clone()));
            if linked {
                // Child is in the same group as spawner.
                // Child's ancestors are spawner's ancestors.
                Some((spawner_group.tasks.clone(), ancestors))
            } else {
                // Child is in a separate group from spawner.
                let g = Exclusive::new(Some(TaskGroupData {
                    members:     TaskSet::new(),
                    descendants: TaskSet::new(),
                }));
                let a = if supervised {
                    let new_generation = incr_generation(&ancestors);
                    assert!(new_generation < uint::max_value);
                    // Child's ancestors start with the spawner.
                    // Build a new node in the ancestor list.
                    AncestorList(Some(Exclusive::new(AncestorNode {
                        generation: new_generation,
                        parent_group: spawner_group.tasks.clone(),
                        ancestors: ancestors,
                    })))
                } else {
                    // Child has no ancestors.
                    AncestorList(None)
                };
                Some((g, a))
            }
        }
    } else {
        None
    }
}

// Set up membership in taskgroup and descendantship in all ancestor
// groups. If any enlistment fails, Some task was already failing, so
// don't let the child task run, and undo every successful enlistment.
fn enlist_many(child: &KillHandle, child_arc: &TaskGroupArc,
               ancestors: &mut AncestorList) -> bool {
    // Join this taskgroup.
    let mut result = do access_group(child_arc) |child_tg| {
        enlist_in_taskgroup(child_tg, child.clone(), true) // member
    };
    if result {
        // Unwinding function in case any ancestral enlisting fails
        let bail: &fn(TaskGroupInner) = |tg| { leave_taskgroup(tg, child, false) };
        // Attempt to join every ancestor group.
        result = do each_ancestor(ancestors, bail) |ancestor_tg| {
            // Enlist as a descendant, not as an actual member.
            // Descendants don't kill ancestor groups on failure.
            enlist_in_taskgroup(ancestor_tg, child.clone(), false)
        };
        // If any ancestor group fails, need to exit this group too.
        if !result {
            do access_group(child_arc) |child_tg| {
                leave_taskgroup(child_tg, child, true); // member
            }
        }
    }
    result
}

pub fn spawn_raw(mut opts: TaskOpts, f: ~fn()) {
    use rt::sched::*;

    rtassert!(in_green_task_context());

    let child_data = Cell::new(gen_child_taskgroup(opts.linked, opts.supervised));
    let indestructible = opts.indestructible;

    let child_wrapper: ~fn() = || {
        // Child task runs this code.

        // If child data is 'None', the enlist is vacuously successful.
        let enlist_success = do child_data.take().map_move_default(true) |child_data| {
            let child_data = Cell::new(child_data); // :(
            do Local::borrow |me: &mut Task| {
                let (child_tg, ancestors) = child_data.take();
                let mut ancestors = ancestors;
                let handle = me.death.kill_handle.get_ref();
                // Atomically try to get into all of our taskgroups.
                if enlist_many(handle, &child_tg, &mut ancestors) {
                    // Got in. We can run the provided child body, and can also run
                    // the taskgroup's exit-time-destructor afterward.
                    me.taskgroup = Some(Taskgroup(child_tg, ancestors, None));
                    true
                } else {
                    false
                }
            }
        };
        // Should be run after the local-borrowed task is returned.
        if enlist_success {
            if indestructible {
                do unkillable { f() }
            } else {
                f()
            }
        }
    };

    let mut task = if opts.sched.mode != SingleThreaded {
        if opts.watched {
            Task::build_child(opts.stack_size, child_wrapper)
        } else {
            Task::build_root(opts.stack_size, child_wrapper)
        }
    } else {
        unsafe {
            // Creating a 1:1 task:thread ...
            let sched: *mut Scheduler = Local::unsafe_borrow();
            let sched_handle = (*sched).make_handle();

            // Since this is a 1:1 scheduler we create a queue not in
            // the stealee set. The run_anything flag is set false
            // which will disable stealing.
            let work_queue = WorkQueue::new();

            // Create a new scheduler to hold the new task
            let new_loop = ~UvEventLoop::new();
            let mut new_sched = ~Scheduler::new_special(new_loop,
                                                        work_queue,
                                                        (*sched).work_queues.clone(),
                                                        (*sched).sleeper_list.clone(),
                                                        false,
                                                        Some(sched_handle));
            let mut new_sched_handle = new_sched.make_handle();

            // Allow the scheduler to exit when the pinned task exits
            new_sched_handle.send(Shutdown);

            // Pin the new task to the new scheduler
            let new_task = if opts.watched {
                Task::build_homed_child(opts.stack_size, child_wrapper, Sched(new_sched_handle))
            } else {
                Task::build_homed_root(opts.stack_size, child_wrapper, Sched(new_sched_handle))
            };

            // Create a task that will later be used to join with the new scheduler
            // thread when it is ready to terminate
            let (thread_port, thread_chan) = oneshot();
            let thread_port_cell = Cell::new(thread_port);
            let join_task = do Task::build_child(None) {
                rtdebug!("running join task");
                let thread_port = thread_port_cell.take();
                let thread: Thread = thread_port.recv();
                thread.join();
            };

            // Put the scheduler into another thread
            let new_sched_cell = Cell::new(new_sched);
            let orig_sched_handle_cell = Cell::new((*sched).make_handle());
            let join_task_cell = Cell::new(join_task);

            let thread = do Thread::start {
                let mut new_sched = new_sched_cell.take();
                let mut orig_sched_handle = orig_sched_handle_cell.take();
                let join_task = join_task_cell.take();

                let bootstrap_task = ~do Task::new_root(&mut new_sched.stack_pool, None) || {
                    rtdebug!("boostrapping a 1:1 scheduler");
                };
                new_sched.bootstrap(bootstrap_task);

                rtdebug!("enqueing join_task");
                // Now tell the original scheduler to join with this thread
                // by scheduling a thread-joining task on the original scheduler
                orig_sched_handle.send(TaskFromFriend(join_task));

                // NB: We can't simply send a message from here to another task
                // because this code isn't running in a task and message passing doesn't
                // work outside of tasks. Hence we're sending a scheduler message
                // to execute a new task directly to a scheduler.
            };

            // Give the thread handle to the join task
            thread_chan.send(thread);

            // When this task is enqueued on the current scheduler it will then get
            // forwarded to the scheduler to which it is pinned
            new_task
        }
    };

    if opts.notify_chan.is_some() {
        let notify_chan = opts.notify_chan.take_unwrap();
        let notify_chan = Cell::new(notify_chan);
        let on_exit: ~fn(bool) = |success| {
            notify_chan.take().send(
                if success { Success } else { Failure }
            )
        };
        task.death.on_exit = Some(on_exit);
    }

    task.name = opts.name.take();
    rtdebug!("spawn calling run_task");
    Scheduler::run_task(task);

}

#[test]
fn test_spawn_raw_simple() {
    let (po, ch) = stream();
    do spawn_raw(default_task_opts()) {
        ch.send(());
    }
    po.recv();
}

#[test]
fn test_spawn_raw_unsupervise() {
    let opts = task::TaskOpts {
        linked: false,
        watched: false,
        notify_chan: None,
        .. default_task_opts()
    };
    do spawn_raw(opts) {
        fail!();
    }
}

#[test]
fn test_spawn_raw_notify_success() {
    let (notify_po, notify_ch) = comm::stream();

    let opts = task::TaskOpts {
        notify_chan: Some(notify_ch),
        .. default_task_opts()
    };
    do spawn_raw(opts) {
    }
    assert_eq!(notify_po.recv(), Success);
}

#[test]
fn test_spawn_raw_notify_failure() {
    // New bindings for these
    let (notify_po, notify_ch) = comm::stream();

    let opts = task::TaskOpts {
        linked: false,
        watched: false,
        notify_chan: Some(notify_ch),
        .. default_task_opts()
    };
    do spawn_raw(opts) {
        fail!();
    }
    assert_eq!(notify_po.recv(), Failure);
}