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std::rt: Don't allow schedulers to exit before handling all messages

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Every time run_sched_once performs a 'scheduling action' it needs to guarantee
that it runs at least one more time, so enqueue another run_sched_once callback.
The primary reason it needs to do this is because not all async callbacks
are guaranteed to run, it's only guaranteed that *a* callback will run after
enqueing one - some may get dropped.

At the moment this means we wastefully create lots of callbacks to ensure that
there will *definitely* be a callback queued up to continue running the scheduler.
The logic really needs to be tightened up here.
This commit is contained in:
Brian Anderson 2013-08-03 23:29:21 -07:00
parent f0f7e1b3fc
commit a27f339cb4
1 changed files with 10 additions and 0 deletions
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10
src/libstd/rt/sched.rs
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@ -172,6 +172,10 @@ impl Scheduler {
rtdebug!("stopping scheduler %u", stask.sched.get_ref().sched_id());
// Should not have any messages
let message = stask.sched.get_mut_ref().message_queue.pop();
assert!(message.is_none());
stask.destroyed = true;
}
@ -336,11 +340,14 @@ impl Scheduler {
match this.message_queue.pop() {
Some(PinnedTask(task)) => {
let mut task = task;
this.event_loop.callback(Scheduler::run_sched_once);
task.give_home(Sched(this.make_handle()));
this.resume_task_immediately(task);
return None;
}
Some(TaskFromFriend(task)) => {
this.event_loop.callback(Scheduler::run_sched_once);
rtdebug!("got a task from a friend. lovely!");
return this.sched_schedule_task(task);
}
Some(Wake) => {
@ -395,6 +402,7 @@ impl Scheduler {
/// Take a non-homed task we aren't allowed to run here and send
/// it to the designated friend scheduler to execute.
fn send_to_friend(&mut self, task: ~Task) {
rtdebug!("sending a task to friend");
match self.friend_handle {
Some(ref mut handle) => {
handle.send(TaskFromFriend(task));
@ -426,12 +434,14 @@ impl Scheduler {
Scheduler::send_task_home(task);
return Some(this);
} else {
this.event_loop.callback(Scheduler::run_sched_once);
task.give_home(Sched(home_handle));
this.resume_task_immediately(task);
return None;
}
}
AnySched if this.run_anything => {
this.event_loop.callback(Scheduler::run_sched_once);
task.give_home(AnySched);
this.resume_task_immediately(task);
return None;