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Fix select deschedule environment race for real this time, in light of task killing.

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This commit is contained in:
Ben Blum 2013-08-13 17:31:13 -04:00
parent 0d817ee869
commit 65cf75af67
1 changed files with 24 additions and 19 deletions
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43
src/libstd/select.rs
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@ -20,6 +20,7 @@ use rt::select::{SelectInner, SelectPortInner};
use rt::local::Local;
use rt::rtio::EventLoop;
use task;
use unstable::finally::Finally;
use vec::{OwnedVector, MutableVector};
/// Trait for message-passing primitives that can be select()ed on.
@ -57,27 +58,31 @@ pub fn select<A: Select>(ports: &mut [A]) -> uint {
let p = Cell::new(p);
let c = Cell::new(c);
let sched = Local::take::<Scheduler>();
do sched.deschedule_running_task_and_then |sched, task| {
let task_handles = task.make_selectable(ports.len());
for (index, (port, task_handle)) in
ports.mut_iter().zip(task_handles.move_iter()).enumerate() {
// If one of the ports has data by now, it will wake the handle.
if port.block_on(sched, task_handle) {
ready_index = index;
break;
}
}
do (|| {
let c = Cell::new(c.take());
do sched.event_loop.callback { c.take().send_deferred(()) }
}
let sched = Local::take::<Scheduler>();
do sched.deschedule_running_task_and_then |sched, task| {
let task_handles = task.make_selectable(ports.len());
// Unkillable is necessary not because getting killed is dangerous here,
// but to force the recv not to use the same kill-flag that we used for
// selecting. Otherwise a user-sender could spuriously wakeup us here.
do task::unkillable { p.take().recv(); }
for (index, (port, task_handle)) in
ports.mut_iter().zip(task_handles.move_iter()).enumerate() {
// If one of the ports has data by now, it will wake the handle.
if port.block_on(sched, task_handle) {
ready_index = index;
break;
}
}
let c = Cell::new(c.take());
do sched.event_loop.callback { c.take().send_deferred(()) }
}
}).finally {
let p = Cell::new(p.take());
// Unkillable is necessary not because getting killed is dangerous here,
// but to force the recv not to use the same kill-flag that we used for
// selecting. Otherwise a user-sender could spuriously wakeup us here.
do task::unkillable { p.take().recv(); }
}
// Task resumes. Now unblock ourselves from all the ports we blocked on.
// If the success index wasn't reset, 'take' will just take all of them.