introduce new queue for terminated fibers

include/boost/fiber/detail/terminated_queue.hpp

@@ -0,0 +1,62 @@
+
+//          Copyright Oliver Kowalke 2013.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_FIBERS_DETAIL_TERMINATED_QUEUE_H
+#define BOOST_FIBERS_DETAIL_TERMINATED_QUEUE_H
+
+#include <algorithm>
+#include <cstddef>
+
+#include <boost/config.hpp>
+
+#include <boost/fiber/detail/config.hpp>
+
+#ifdef BOOST_HAS_ABI_HEADERS
+#  include BOOST_ABI_PREFIX
+#endif
+
+namespace boost {
+namespace fibers {
+
+class fiber_context;
+
+namespace detail {
+
+class terminated_queue {
+public:
+    terminated_queue() noexcept :
+        head_( nullptr),
+        tail_( & head_) {
+    }
+
+    terminated_queue( terminated_queue const&) = delete;
+    terminated_queue & operator=( terminated_queue const&) = delete;
+
+    void push( fiber_context * item) noexcept;
+
+    void clear() noexcept;
+
+    void swap( terminated_queue & other) {
+        std::swap( head_, other.head_);
+        std::swap( tail_, other.tail_);
+    }
+
+private:
+    fiber_context   *   head_;
+    // tail_ points to the nxt field that contains the null that marks the end
+    // of the terminated_queue. When the terminated_queue is empty, tail_ points to head_. tail_ must
+    // never be null: it always points to a real fiber_context*. However, in
+    // normal use, (*tail_) is always null.
+    fiber_context   **  tail_;
+};
+
+}}}
+
+#ifdef BOOST_HAS_ABI_HEADERS
+#  include BOOST_ABI_SUFFIX
+#endif
+
+#endif // BOOST_FIBERS_DETAIL_TERMINATED_QUEUE_H

include/boost/fiber/fiber_manager.hpp

@@ -14,8 +14,8 @@
 
 #include <boost/fiber/detail/config.hpp>
 #include <boost/fiber/detail/convert.hpp>
-#include <boost/fiber/detail/fifo.hpp>
 #include <boost/fiber/detail/spinlock.hpp>
+#include <boost/fiber/detail/terminated_queue.hpp>
 #include <boost/fiber/detail/waiting_queue.hpp>
 
 #ifdef BOOST_HAS_ABI_HEADERS
@@ -31,7 +31,7 @@ struct sched_algorithm;
 struct fiber_manager {
 private:
     typedef detail::waiting_queue                   wqueue_t;
-    typedef detail::fifo                            tqueue_t;
+    typedef detail::terminated_queue                tqueue_t;
 
     sched_algorithm                             *   sched_algo_;
     fiber_context                               *   active_fiber_;