2 files changed, 56 insertions, 0 deletions
diff --git a/src/libstd/rt/bookkeeping.rs b/src/libstd/rt/bookkeeping.rs
new file mode 100644
index 00000000000..5851a6a39c6
--- /dev/null
+++ b/src/libstd/rt/bookkeeping.rs
@@ -0,0 +1,52 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Task bookkeeping
+//!
+//! This module keeps track of the number of running tasks so that entry points
+//! with libnative know when it's possible to exit the program (once all tasks
+//! have exited).
+//!
+//! The green counterpart for this is bookkeeping on sched pools, and it's up to
+//! each respective runtime to make sure that they call increment() and
+//! decrement() manually.
+
+#[experimental]; // this is a massive code smell
+#[doc(hidden)];
+
+use sync::atomics;
+use unstable::mutex::{StaticNativeMutex, NATIVE_MUTEX_INIT};
+
+static mut TASK_COUNT: atomics::AtomicUint = atomics::INIT_ATOMIC_UINT;
+static mut TASK_LOCK: StaticNativeMutex = NATIVE_MUTEX_INIT;
+
+pub fn increment() {
+    let _ = unsafe { TASK_COUNT.fetch_add(1, atomics::SeqCst) };
+}
+
+pub fn decrement() {
+    unsafe {
+        if TASK_COUNT.fetch_sub(1, atomics::SeqCst) == 1 {
+            let mut guard = TASK_LOCK.lock();
+            guard.signal();
+        }
+    }
+}
+
+/// Waits for all other native tasks in the system to exit. This is only used by
+/// the entry points of native programs
+pub fn wait_for_other_tasks() {
+    unsafe {
+        let mut guard = TASK_LOCK.lock();
+        while TASK_COUNT.load(atomics::SeqCst) > 0 {
+            guard.wait();
+        }
+    }
+}
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index 2f1a6989092..459bc061c56 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -128,6 +128,9 @@ pub mod args;
 // Support for running procedures when a program has exited.
 mod at_exit_imp;
 
+// Bookkeeping for task counts
+pub mod bookkeeping;
+
 // Stack overflow protection
 pub mod stack;
 
@@ -207,6 +210,7 @@ pub fn at_exit(f: proc()) {
 /// Invoking cleanup while portions of the runtime are still in use may cause
 /// undefined behavior.
 pub unsafe fn cleanup() {
+    bookkeeping::wait_for_other_tasks();
     at_exit_imp::run();
     args::cleanup();
     local_ptr::cleanup();