rt: Add a hack to fix a port detach bug

Author: brson

src/libcore/comm.rs

@@ -44,6 +44,7 @@ native mod rustrt {
     fn del_port(po: *rust_port);
     fn rust_port_begin_detach(po: *rust_port,
                               yield: *ctypes::uintptr_t);
+    fn rust_port_end_detach(po: *rust_port);
     fn get_port_id(po: *rust_port) -> port_id;
     fn rust_port_size(po: *rust_port) -> ctypes::size_t;
     fn port_recv(dptr: *uint, po: *rust_port,
@@ -92,6 +93,7 @@ resource port_ptr<T: send>(po: *rust_port) {
         // in a bogus state.
         task::yield();
     }
+    rustrt::rust_port_end_detach(po);
 
     // Drain the port so that all the still-enqueued items get dropped
     while rustrt::rust_port_size(po) > 0u {

src/rt/rust_builtin.cpp

@@ -488,12 +488,16 @@ rust_port_begin_detach(rust_port *port, uintptr_t *yield) {
     port->begin_detach(yield);
 }
 
+extern "C" CDECL void
+rust_port_end_detach(rust_port *port) {
+    port->end_detach();
+}
+
 extern "C" CDECL void
 del_port(rust_port *port) {
     rust_task *task = rust_task_thread::get_task();
     LOG(task, comm, "del_port(0x%" PRIxPTR ")", (uintptr_t) port);
     A(task->thread, port->get_ref_count() == 0, "Expected port ref_count == 0");
-    port->end_detach();
     delete port;
 }
 

src/rt/rust_port.cpp

@@ -44,6 +44,10 @@ void rust_port::begin_detach(uintptr_t *yield) {
 }
 
 void rust_port::end_detach() {
+    // FIXME: For some reason we can sometimes get here without the
+    // refcount decreasing to 0. This is definitely a bug
+    while (get_ref_count() != 0) { }
+
     // Just take the lock to make sure that the thread that signaled
     // the detach_cond isn't still holding it
     scoped_lock with(detach_lock);

src/rt/rustrt.def.in

@@ -35,6 +35,7 @@ rust_list_files
 rust_log_console_on
 rust_log_console_off
 rust_port_begin_detach
+rust_port_end_detach
 rust_port_size
 rust_process_wait
 rust_ptr_eq