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Clean up transitionary glue in task/spawn.rs. Don't hold kill-little-lock for O(n) time, cf #3100, and optimize out several unneeded clone()s.

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This commit is contained in:
Ben Blum 2013-08-12 14:54:09 -04:00
parent ce48e71d28
commit 5ac8c57bd4
4 changed files with 69 additions and 138 deletions
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4
src/libstd/rt/kill.rs
View File

@ -488,8 +488,8 @@ impl Death {
rtassert!(self.unkillable == 0);
self.unkillable = 1;
// FIXME(#7544): See corresponding fixme at the callsite in task.rs.
// NB(#8192): Doesn't work with "let _ = ..."
// NB. See corresponding comment at the callsite in task.rs.
// FIXME(#8192): Doesn't work with "let _ = ..."
{ use util; util::ignore(group); }
// Step 1. Decide if we need to collect child failures synchronously.

10
src/libstd/rt/task.rs
View File

@ -253,12 +253,10 @@ impl Task {
}
}
// FIXME(#7544): We pass the taskgroup into death so that it can be
// dropped while the unkillable counter is set. This should not be
// necessary except for an extraneous clone() in task/spawn.rs that
// causes a killhandle to get dropped, which mustn't receive a kill
// signal since we're outside of the unwinder's try() scope.
// { let _ = self.taskgroup.take(); }
// NB. We pass the taskgroup into death so that it can be dropped while
// the unkillable counter is set. This is necessary for when the
// taskgroup destruction code drops references on KillHandles, which
// might require using unkillable (to synchronize with an unwrapper).
self.death.collect_failure(!self.unwinder.unwinding, self.taskgroup.take());
self.destroyed = true;
}

1
src/libstd/task/mod.rs
View File

@ -38,7 +38,6 @@
use prelude::*;
use cell::Cell;
use cmp::Eq;
use comm::{stream, Chan, GenericChan, GenericPort, Port};
use result::Result;
use result;

192
src/libstd/task/spawn.rs
View File

@ -22,10 +22,9 @@
*
* A new one of these is created each spawn_linked or spawn_supervised.
*
* (2) The "tcb" 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), a flag for
* whether it's part of the 'main'/'root' taskgroup, and an optionally
* (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
@ -84,7 +83,6 @@ use local_data;
use task::{Failure, SingleThreaded};
use task::{Success, TaskOpts, TaskResult};
use task::unkillable;
use to_bytes::IterBytes;
use uint;
use util;
use unstable::sync::Exclusive;
@ -101,29 +99,7 @@ use rt::work_queue::WorkQueue;
#[cfg(test)] use comm;
#[cfg(test)] use task;
// Transitionary.
#[deriving(Eq)]
enum TaskHandle {
NewTask(KillHandle),
}
impl Clone for TaskHandle {
fn clone(&self) -> TaskHandle {
match *self {
NewTask(ref x) => NewTask(x.clone()),
}
}
}
impl IterBytes for TaskHandle {
fn iter_bytes(&self, lsb0: bool, f: &fn(buf: &[u8]) -> bool) -> bool {
match *self {
NewTask(ref x) => x.iter_bytes(lsb0, f),
}
}
}
struct TaskSet(HashSet<TaskHandle>);
struct TaskSet(HashSet<KillHandle>);
impl TaskSet {
#[inline]
@ -131,17 +107,17 @@ impl TaskSet {
TaskSet(HashSet::new())
}
#[inline]
fn insert(&mut self, task: TaskHandle) {
fn insert(&mut self, task: KillHandle) {
let didnt_overwrite = (**self).insert(task);
assert!(didnt_overwrite);
}
#[inline]
fn remove(&mut self, task: &TaskHandle) {
fn remove(&mut self, task: &KillHandle) {
let was_present = (**self).remove(task);
assert!(was_present);
}
#[inline]
fn move_iter(self) -> HashSetMoveIterator<TaskHandle> {
fn move_iter(self) -> HashSetMoveIterator<KillHandle> {
(*self).move_iter()
}
}
@ -291,7 +267,7 @@ fn each_ancestor(list: &mut AncestorList,
None => nobe_is_dead
};
// Call iterator block. (If the group is dead, it's
// safe to skip it. This will leave our TaskHandle
// 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.)
@ -338,7 +314,6 @@ pub struct Taskgroup {
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,
is_main: bool,
notifier: Option<AutoNotify>,
}
@ -355,14 +330,18 @@ impl Drop for Taskgroup {
for x in this.notifier.mut_iter() {
x.failed = true;
}
// Take everybody down with us.
do access_group(&self.tasks) |tg| {
kill_taskgroup(tg, &me, self.is_main);
}
// 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);
leave_taskgroup(tg, me, true);
}
}
// It doesn't matter whether this happens before or after dealing
@ -370,7 +349,7 @@ impl Drop for Taskgroup {
// 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);
leave_taskgroup(ancestor_group, me, false);
true
};
}
@ -380,7 +359,6 @@ impl Drop for Taskgroup {
pub fn Taskgroup(tasks: TaskGroupArc,
ancestors: AncestorList,
is_main: bool,
mut notifier: Option<AutoNotify>) -> Taskgroup {
for x in notifier.mut_iter() {
x.failed = false;
@ -389,7 +367,6 @@ pub fn Taskgroup(tasks: TaskGroupArc,
Taskgroup {
tasks: tasks,
ancestors: ancestors,
is_main: is_main,
notifier: notifier
}
}
@ -413,7 +390,7 @@ fn AutoNotify(chan: Chan<TaskResult>) -> AutoNotify {
}
}
fn enlist_in_taskgroup(state: TaskGroupInner, me: TaskHandle,
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.
@ -428,8 +405,7 @@ fn enlist_in_taskgroup(state: TaskGroupInner, me: TaskHandle,
}
// NB: Runs in destructor/post-exit context. Can't 'fail'.
fn leave_taskgroup(state: TaskGroupInner, me: &TaskHandle,
is_member: bool) {
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| {
@ -442,43 +418,23 @@ fn leave_taskgroup(state: TaskGroupInner, me: &TaskHandle,
}
// NB: Runs in destructor/post-exit context. Can't 'fail'.
fn kill_taskgroup(state: TaskGroupInner, me: &TaskHandle, is_main: bool) {
unsafe {
// NB: We could do the killing iteration outside of the group arc, by
// having "let mut newstate" here, swapping inside, and iterating
// after. But that would let other exiting tasks fall-through and exit
// while we were trying to kill them, causing potential
// use-after-free. A task's presence in the arc guarantees it's alive
// only while we hold the lock, so if we're failing, all concurrently
// exiting tasks must wait for us. To do it differently, we'd have to
// use the runtime's task refcounting, but that could leave task
// structs around long after their task exited.
let newstate = util::replace(state, None);
// 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.)
if newstate.is_some() {
let TaskGroupData { members: members, descendants: descendants } =
newstate.unwrap();
for sibling in members.move_iter() {
// Skip self - killing ourself won't do much good.
if &sibling != me {
RuntimeGlue::kill_task(sibling);
}
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);
}
// Only one task should ever do this.
if is_main {
RuntimeGlue::kill_all_tasks(me);
}
// Do NOT restore state to Some(..)! It stays None to indicate
// that the whole taskgroup is failing, to forbid new spawns.
}
// (note: multiple tasks may reach this point)
}
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
@ -490,38 +446,23 @@ fn taskgroup_key() -> local_data::Key<@@mut Taskgroup> {
// Transitionary.
struct RuntimeGlue;
impl RuntimeGlue {
unsafe fn kill_task(task: TaskHandle) {
match task {
NewTask(handle) => {
let mut handle = handle;
do handle.kill().map_move |killed_task| {
let killed_task = Cell::new(killed_task);
do Local::borrow::<Scheduler, ()> |sched| {
sched.enqueue_task(killed_task.take());
}
};
fn kill_task(handle: KillHandle) {
let mut handle = handle;
do handle.kill().map_move |killed_task| {
let killed_task = Cell::new(killed_task);
do Local::borrow::<Scheduler, ()> |sched| {
sched.enqueue_task(killed_task.take());
}
}
};
}
unsafe fn kill_all_tasks(task: &TaskHandle) {
match *task {
// FIXME(#7544): Remove the kill_all feature entirely once the
// oldsched goes away.
NewTask(ref _handle) => rtabort!("can't kill_all in newsched"),
}
}
fn with_task_handle_and_failing(blk: &fn(TaskHandle, bool)) {
fn with_task_handle_and_failing(blk: &fn(&KillHandle, bool)) {
if 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 = Local::unsafe_borrow::<Task>();
// FIXME(#7544): Get rid of this clone by passing by-ref.
// Will probably have to wait until the old rt is gone.
blk(NewTask((*me).death.kill_handle.get_ref().clone()),
(*me).unwinder.unwinding)
blk((*me).death.kill_handle.get_ref(), (*me).unwinder.unwinding)
}
} else {
rtabort!("task dying in bad context")
@ -540,15 +481,12 @@ impl RuntimeGlue {
// Lazily initialize.
let mut members = TaskSet::new();
let my_handle = (*me).death.kill_handle.get_ref().clone();
members.insert(NewTask(my_handle));
members.insert(my_handle);
let tasks = Exclusive::new(Some(TaskGroupData {
members: members,
descendants: TaskSet::new(),
}));
// FIXME(#7544): Remove the is_main flag entirely once
// the newsched goes away. The main taskgroup has no special
// behaviour.
let group = Taskgroup(tasks, AncestorList(None), false, None);
let group = Taskgroup(tasks, AncestorList(None), None);
(*me).taskgroup = Some(group);
(*me).taskgroup.get_ref()
}
@ -563,9 +501,7 @@ impl RuntimeGlue {
// 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, bool)> {
// FIXME(#7544): Not safe to lazily initialize in the old runtime. Remove
// this context check once 'spawn_raw_oldsched' is gone.
-> 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.
@ -574,8 +510,7 @@ fn gen_child_taskgroup(linked: bool, supervised: bool)
if linked {
// Child is in the same group as spawner.
// Child's ancestors are spawner's ancestors.
// Propagate main-ness.
Some((spawner_group.tasks.clone(), ancestors, spawner_group.is_main))
Some((spawner_group.tasks.clone(), ancestors))
} else {
// Child is in a separate group from spawner.
let g = Exclusive::new(Some(TaskGroupData {
@ -596,7 +531,7 @@ fn gen_child_taskgroup(linked: bool, supervised: bool)
// Child has no ancestors.
AncestorList(None)
};
Some((g, a, false))
Some((g, a))
}
}
} else {
@ -607,7 +542,7 @@ fn gen_child_taskgroup(linked: bool, supervised: bool)
// 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: TaskHandle, child_arc: &TaskGroupArc,
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| {
@ -615,7 +550,7 @@ fn enlist_many(child: TaskHandle, child_arc: &TaskGroupArc,
};
if result {
// Unwinding function in case any ancestral enlisting fails
let bail: &fn(TaskGroupInner) = |tg| { leave_taskgroup(tg, &child, false) };
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.
@ -625,7 +560,7 @@ fn enlist_many(child: TaskHandle, child_arc: &TaskGroupArc,
// 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
leave_taskgroup(child_tg, child, true); // member
}
}
}
@ -653,15 +588,14 @@ fn spawn_raw_newsched(mut opts: TaskOpts, f: ~fn()) {
let enlist_success = do child_data.take().map_move_default(true) |child_data| {
let child_data = Cell::new(child_data); // :(
do Local::borrow::<Task, bool> |me| {
let (child_tg, ancestors, is_main) = child_data.take();
let (child_tg, ancestors) = child_data.take();
let mut ancestors = ancestors;
// FIXME(#7544): Optimize out the xadd in this clone, somehow.
let handle = me.death.kill_handle.get_ref().clone();
let handle = me.death.kill_handle.get_ref();
// Atomically try to get into all of our taskgroups.
if enlist_many(NewTask(handle), &child_tg, &mut ancestors) {
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, is_main, None));
me.taskgroup = Some(Taskgroup(child_tg, ancestors, None));
true
} else {
false
@ -678,14 +612,14 @@ fn spawn_raw_newsched(mut opts: TaskOpts, f: ~fn()) {
}
};
let mut task = unsafe {
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)
}
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 = Local::unsafe_borrow::<Scheduler>();
let sched_handle = (*sched).make_handle();