auto merge of #8195 : bblum/rust/task-cleanup, r=brson

In the first commit it is obvious why some of the barriers can be changed to ```Relaxed```, but it is not as obvious for the once I changed in ```kill.rs```. The rationale for those is documented as part of the documenting commit.

Also the last commit is a temporary hack to prevent kill signals from being received in taskgroup cleanup code, which could be fixed in a more principled way once the old runtime is gone.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/libstd/rt/task.rs b/src/libstd/rt/task.rs
index 23a0d28e457..b242ee13fa6 100644
--- a/src/libstd/rt/task.rs
+++ b/src/libstd/rt/task.rs
@@ -212,8 +212,13 @@ impl Task {
     pub fn run(&mut self, f: &fn()) {
         rtdebug!("run called on task: %u", borrow::to_uint(self));
         self.unwinder.try(f);
-        { let _ = self.taskgroup.take(); }
-        self.death.collect_failure(!self.unwinder.unwinding);
+        // 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(); }
+        self.death.collect_failure(!self.unwinder.unwinding, self.taskgroup.take());
         self.destroy();
     }