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

src/libstd/select.rs

@@ -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.
@@ -57,6 +58,8 @@ pub fn select<A: Select>(ports: &mut [A]) -> uint {
     let p = Cell::new(p);
     let c = Cell::new(c);
 
+    do (|| {
+        let c = Cell::new(c.take());
         let sched = Local::take::<Scheduler>();
         do sched.deschedule_running_task_and_then |sched, task| {
             let task_handles = task.make_selectable(ports.len());
@@ -73,11 +76,13 @@ pub fn select<A: Select>(ports: &mut [A]) -> uint {
             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.