diff --git a/build/Jamfile.v2 b/build/Jamfile.v2
index 3699a75f..164906c7 100644
--- a/build/Jamfile.v2
+++ b/build/Jamfile.v2
@@ -36,7 +36,6 @@ lib boost_fibers
       condition.cpp
       detail/fiber_base.cpp
       detail/scheduler.cpp
-      detail/spinlock.cpp
       fiber.cpp
       future.cpp
       interruption.cpp
diff --git a/include/boost/fiber/algorithm.hpp b/include/boost/fiber/algorithm.hpp
index 28d1e900..996f07b6 100644
--- a/include/boost/fiber/algorithm.hpp
+++ b/include/boost/fiber/algorithm.hpp
@@ -14,7 +14,6 @@
 
 #include <boost/fiber/detail/config.hpp>
 #include <boost/fiber/detail/notify.hpp>
-#include <boost/fiber/detail/spinlock.hpp>
 #include <boost/fiber/fiber.hpp>
 
 #ifdef BOOST_HAS_ABI_HEADERS
@@ -41,7 +40,7 @@ struct BOOST_FIBERS_DECL algorithm : private noncopyable
 
     virtual bool run() = 0;
 
-    virtual void wait( unique_lock< detail::spinlock > &) = 0;
+    virtual void wait() = 0;
 
     virtual void yield() = 0;
 
diff --git a/include/boost/fiber/bounded_channel.hpp b/include/boost/fiber/bounded_channel.hpp
index 584b71cd..9a90183c 100644
--- a/include/boost/fiber/bounded_channel.hpp
+++ b/include/boost/fiber/bounded_channel.hpp
@@ -12,7 +12,6 @@
 #include <cstddef>
 #include <stdexcept>
 
-#include <boost/atomic.hpp>
 #include <boost/chrono/system_clocks.hpp>
 #include <boost/config.hpp>
 #include <boost/exception/all.hpp>
@@ -73,14 +72,14 @@ private:
     template< typename X >
     friend void intrusive_ptr_release( bounded_channel< X > * p);
 
-    enum state
+    enum state_t
     {
         ACTIVE = 0,
         DEACTIVE
     };
 
-    atomic< state >             state_;
-    atomic< std::size_t >       count_;
+    state_t                     state_;
+    std::size_t                 count_;
     typename node_type::ptr     head_;
     mutable mutex               head_mtx_;
     typename node_type::ptr     tail_;
diff --git a/include/boost/fiber/condition.hpp b/include/boost/fiber/condition.hpp
index 4387b6a9..8976c311 100644
--- a/include/boost/fiber/condition.hpp
+++ b/include/boost/fiber/condition.hpp
@@ -12,7 +12,6 @@
 #include <deque>
 
 #include <boost/assert.hpp>
-#include <boost/atomic.hpp>
 #include <boost/chrono/system_clocks.hpp>
 #include <boost/config.hpp>
 #include <boost/thread/locks.hpp>
@@ -21,7 +20,6 @@
 #include <boost/fiber/detail/config.hpp>
 #include <boost/fiber/detail/notify.hpp>
 #include <boost/fiber/detail/scheduler.hpp>
-#include <boost/fiber/detail/spinlock.hpp>
 #include <boost/fiber/exceptions.hpp>
 #include <boost/fiber/interruption.hpp>
 #include <boost/fiber/mutex.hpp>
@@ -42,7 +40,6 @@ namespace fibers {
 class BOOST_FIBERS_DECL condition : private noncopyable
 {
 private:
-    detail::spinlock                       splk_;
     std::deque< detail::notify::ptr_t >    waiting_;
 
 public:
@@ -70,12 +67,11 @@ public:
             if ( n)
             {
                 // store this fiber in order to be notified later
-                unique_lock< detail::spinlock > lk( splk_);
                 waiting_.push_back( n);
                 lt.unlock();
 
                 // suspend fiber
-                detail::scheduler::instance().wait( lk);
+                detail::scheduler::instance().wait();
 
                 // check if fiber was interrupted
                 this_fiber::interruption_point();
@@ -85,9 +81,7 @@ public:
                 // notifier for main-fiber
                 n = detail::scheduler::instance().notifier();
                 // store this fiber in order to be notified later
-                unique_lock< detail::spinlock > lk( splk_);
                 waiting_.push_back( n);
-                lk.unlock();
 
                 lt.unlock();
                 while ( ! n->is_ready() )
@@ -100,7 +94,6 @@ public:
         catch (...)
         {
             // remove fiber from waiting_
-            unique_lock< detail::spinlock > lk( splk_);
             waiting_.erase(
                 std::find( waiting_.begin(), waiting_.end(), n) );
             throw;
diff --git a/include/boost/fiber/detail/fiber_base.hpp b/include/boost/fiber/detail/fiber_base.hpp
index ad6436ed..a343ea0e 100644
--- a/include/boost/fiber/detail/fiber_base.hpp
+++ b/include/boost/fiber/detail/fiber_base.hpp
@@ -11,8 +11,6 @@
 #include <iostream>
 #include <vector>
 
-#include <boost/assert.hpp>
-#include <boost/atomic.hpp>
 #include <boost/chrono/system_clocks.hpp>
 #include <boost/config.hpp>
 #include <boost/context/fcontext.hpp>
@@ -24,7 +22,6 @@
 #include <boost/fiber/detail/config.hpp>
 #include <boost/fiber/detail/flags.hpp>
 #include <boost/fiber/detail/notify.hpp>
-#include <boost/fiber/detail/spinlock.hpp>
 
 #ifdef BOOST_HAS_ABI_HEADERS
 #  include BOOST_ABI_PREFIX
@@ -43,18 +40,20 @@ private:
     template< typename X, typename Y >
     friend class fiber_object;
 
-    static const int READY;
-    static const int RUNNING;
-    static const int WAITING;
-    static const int TERMINATED;
+    enum state_t
+    {
+        READY = 0,
+        RUNNING,
+        WAITING,
+        TERMINATED
+    };
 
-    atomic< int >           state_;
-    atomic< int >           flags_;
-    atomic< int >           priority_;
+    state_t                 state_;
+    int                     flags_;
+    int                     priority_;
     context::fcontext_t     caller_;
     context::fcontext_t *   callee_;
     exception_ptr           except_;
-    spinlock                waiting_mtx_;
     std::vector< ptr_t >    waiting_;
 
 protected:
@@ -193,7 +192,8 @@ public:
         //       - other fiber calls set_ready() on this fiber happend before this
         //         fiber calls set_terminated()
         //       - this fiber stack gets unwound and set_terminated() is called at the end
-        int previous = state_.exchange( TERMINATED);
+        state_t previous = TERMINATED;
+        std::swap( state_, previous);
         BOOST_ASSERT( RUNNING == previous);
         //BOOST_ASSERT( RUNNING == previous || READY == previous);
     }
@@ -219,13 +219,15 @@ public:
         if ( result || TERMINATED == expected || READY == expected) return;
     }
 #endif
-        int previous = state_.exchange( READY);
+        state_t previous = READY;
+        std::swap( state_, previous);
         BOOST_ASSERT( WAITING == previous || RUNNING == previous || READY == previous);
     }
 
     void set_running() BOOST_NOEXCEPT
     {
-        int previous = state_.exchange( RUNNING);
+        state_t previous = RUNNING;
+        std::swap( state_, previous);
         BOOST_ASSERT( READY == previous);
     }
 
@@ -240,7 +242,8 @@ public:
         //       - other fiber calls set_ready() on this fiber happend before this
         //         fiber calls set_waiting()
         //       - this fiber might wait on some sync. primitive calling set_waiting()
-        int previous = state_.exchange( WAITING);
+        state_t previous = WAITING;
+        std::swap( state_, previous);
         BOOST_ASSERT( RUNNING == previous);
         //BOOST_ASSERT( RUNNING == previous || READY == previous);
     }
diff --git a/include/boost/fiber/detail/notify.hpp b/include/boost/fiber/detail/notify.hpp
index ddac2ce5..5567b623 100644
--- a/include/boost/fiber/detail/notify.hpp
+++ b/include/boost/fiber/detail/notify.hpp
@@ -10,7 +10,6 @@
 #include <cstddef>
 
 #include <boost/assert.hpp>
-#include <boost/atomic.hpp>
 #include <boost/config.hpp>
 #include <boost/intrusive_ptr.hpp>
 #include <boost/utility.hpp>
@@ -28,7 +27,7 @@ namespace detail {
 class notify : private noncopyable
 {
 private:
-    atomic< std::size_t >   use_count_;
+    std::size_t     use_count_;
 
 public:
     typedef intrusive_ptr< notify >     ptr_t;
diff --git a/include/boost/fiber/detail/spinlock.hpp b/include/boost/fiber/detail/spinlock.hpp
deleted file mode 100644
index ccdb7a1a..00000000
--- a/include/boost/fiber/detail/spinlock.hpp
+++ /dev/null
@@ -1,39 +0,0 @@
-
-//          Copyright Oliver Kowalke 2009.
-// 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)
-//
-//  based on boost::interprocess::sync::interprocess_spin::mutex
-
-#ifndef BOOST_FIBERS_SPINLOCK_H
-#define BOOST_FIBERS_SPINLOCK_H
-
-#include <boost/atomic.hpp>
-#include <boost/utility.hpp>
-
-#include <boost/fiber/detail/config.hpp>
-
-namespace boost {
-namespace fibers {
-namespace detail {
-
-class BOOST_FIBERS_DECL spinlock : private noncopyable
-{
-private:
-	static const int LOCKED;
-	static const int UNLOCKED;
-
-	atomic< int >   state_;
-
-public:
-	spinlock();
-
-	void lock();
-
-	void unlock();
-};
-
-}}}
-
-#endif // BOOST_FIBERS_SPINLOCK_H
diff --git a/include/boost/fiber/future/detail/future_base.hpp b/include/boost/fiber/future/detail/future_base.hpp
index 85006b25..c651ade6 100644
--- a/include/boost/fiber/future/detail/future_base.hpp
+++ b/include/boost/fiber/future/detail/future_base.hpp
@@ -10,7 +10,6 @@
 #include <cstddef>
 
 #include <boost/assert.hpp>
-#include <boost/atomic.hpp>
 #include <boost/config.hpp>
 #include <boost/exception_ptr.hpp>
 #include <boost/intrusive_ptr.hpp>
@@ -36,7 +35,7 @@ template< typename R >
 class future_base : public noncopyable
 {
 private:
-    atomic< std::size_t >   use_count_;
+    std::size_t             use_count_;
     mutable mutex           mtx_;
     mutable condition       waiters_;
     bool                    ready_;
@@ -228,7 +227,7 @@ template< typename R >
 class future_base< R & > : public noncopyable
 {
 private:
-    atomic< std::size_t >   use_count_;
+    std::size_t             use_count_;
     mutable mutex           mtx_;
     mutable condition       waiters_;
     bool                    ready_;
@@ -372,7 +371,7 @@ template<>
 class future_base< void > : public noncopyable
 {
 private:
-    atomic< std::size_t >   use_count_;
+    std::size_t             use_count_;
     mutable mutex           mtx_;
     mutable condition       waiters_;
     bool                    ready_;
diff --git a/include/boost/fiber/future/detail/task_base.hpp b/include/boost/fiber/future/detail/task_base.hpp
index a4f2833d..6773d8e9 100644
--- a/include/boost/fiber/future/detail/task_base.hpp
+++ b/include/boost/fiber/future/detail/task_base.hpp
@@ -9,7 +9,6 @@
 
 #include <cstddef>
 
-#include <boost/atomic.hpp>
 #include <boost/config.hpp>
 #include <boost/intrusive_ptr.hpp>
 #include <boost/throw_exception.hpp>
diff --git a/include/boost/fiber/future/packaged_task.hpp b/include/boost/fiber/future/packaged_task.hpp
index 96d2ddd2..34f16399 100644
--- a/include/boost/fiber/future/packaged_task.hpp
+++ b/include/boost/fiber/future/packaged_task.hpp
@@ -9,7 +9,6 @@
 
 #include <memory>
 
-#include <boost/atomic.hpp>
 #include <boost/config.hpp>
 #include <boost/move/move.hpp>
 #include <boost/throw_exception.hpp>
@@ -40,7 +39,7 @@ private:
 
     typedef void ( dummy::*safe_bool)();
 
-    atomic< bool >  obtained_;
+    bool            obtained_;
     ptr_t           task_;
 
     BOOST_MOVABLE_BUT_NOT_COPYABLE( packaged_task);
@@ -304,7 +303,7 @@ public:
     void swap( packaged_task & other) BOOST_NOEXCEPT
     {
         //TODO: exchange the shared states of two packaged_task
-        obtained_ = other.obtained_.exchange( obtained_.load() );
+        std::swap( obtained_, other.obtained_);
         task_.swap( other.task_);
     }
 
@@ -371,7 +370,7 @@ private:
 
     typedef void ( dummy::*safe_bool)();
 
-    atomic< bool >  obtained_;
+    bool            obtained_;
     ptr_t           task_;
 
     BOOST_MOVABLE_BUT_NOT_COPYABLE( packaged_task);
@@ -635,7 +634,7 @@ public:
     void swap( packaged_task & other) BOOST_NOEXCEPT
     {
         //TODO: exchange the shared states of two packaged_task
-        obtained_ = other.obtained_.exchange( obtained_.load() );
+        std::swap( obtained_, other.obtained_);
         task_.swap( other.task_);
     }
 
diff --git a/include/boost/fiber/future/promise.hpp b/include/boost/fiber/future/promise.hpp
index ca3ff50c..19048301 100644
--- a/include/boost/fiber/future/promise.hpp
+++ b/include/boost/fiber/future/promise.hpp
@@ -9,7 +9,6 @@
 
 #include <memory>
 
-#include <boost/atomic.hpp>
 #include <boost/config.hpp>
 #include <boost/move/move.hpp>
 #include <boost/throw_exception.hpp>
@@ -34,7 +33,7 @@ private:
 
     typedef void ( dummy::*safe_bool)();
 
-    atomic< bool >  obtained_;
+    bool            obtained_;
     ptr_t           future_;
 
     BOOST_MOVABLE_BUT_NOT_COPYABLE( promise);
@@ -124,7 +123,7 @@ public:
     void swap( promise & other) BOOST_NOEXCEPT
     {
         //TODO: exchange the shared states of two promises
-        obtained_ = other.obtained_.exchange( obtained_.load() );
+        std::swap( obtained_, other.obtained_);
         future_.swap( other.future_);
     }
 
@@ -215,7 +214,7 @@ private:
 
     typedef void ( dummy::*safe_bool)();
 
-    atomic< bool >  obtained_;
+    bool            obtained_;
     ptr_t           future_;
 
     BOOST_MOVABLE_BUT_NOT_COPYABLE( promise);
@@ -305,7 +304,7 @@ public:
     void swap( promise & other) BOOST_NOEXCEPT
     {
         //TODO: exchange the shared states of two promises
-        obtained_ = other.obtained_.exchange( obtained_.load() );
+        std::swap( obtained_, other.obtained_);
         future_.swap( other.future_);
     }
 
@@ -368,7 +367,7 @@ private:
 
     typedef void ( dummy::*safe_bool)();
 
-    atomic< bool >  obtained_;
+    bool            obtained_;
     ptr_t           future_;
 
     BOOST_MOVABLE_BUT_NOT_COPYABLE( promise);
@@ -458,7 +457,7 @@ public:
     void swap( promise & other) BOOST_NOEXCEPT
     {
         //TODO: exchange the shared states of two promises
-        obtained_ = other.obtained_.exchange( obtained_.load() );
+        std::swap( obtained_, other.obtained_);
         future_.swap( other.future_);
     }
 
diff --git a/include/boost/fiber/mutex.hpp b/include/boost/fiber/mutex.hpp
index 82585766..0f0b7c5d 100644
--- a/include/boost/fiber/mutex.hpp
+++ b/include/boost/fiber/mutex.hpp
@@ -11,14 +11,12 @@
 
 #include <deque>
 
-#include <boost/atomic.hpp>
 #include <boost/config.hpp>
 #include <boost/thread/locks.hpp>
 #include <boost/utility.hpp>
 
 #include <boost/fiber/detail/config.hpp>
 #include <boost/fiber/detail/notify.hpp>
-#include <boost/fiber/detail/spinlock.hpp>
 
 #ifdef BOOST_HAS_ABI_HEADERS
 #  include BOOST_ABI_PREFIX
@@ -35,11 +33,13 @@ namespace fibers {
 class BOOST_FIBERS_DECL mutex : private noncopyable
 {
 private:
-    static const int LOCKED;
-    static const int UNLOCKED;
+    enum state_t
+    {
+        LOCKED = 0,
+        UNLOCKED
+    };
 
-    atomic< int >                   state_;
-    detail::spinlock                splk_;
+    volatile state_t                state_;
     std::deque<
         detail::notify::ptr_t
     >                               waiting_;
diff --git a/include/boost/fiber/round_robin.hpp b/include/boost/fiber/round_robin.hpp
index 29cad4e1..f6b914d1 100644
--- a/include/boost/fiber/round_robin.hpp
+++ b/include/boost/fiber/round_robin.hpp
@@ -18,7 +18,6 @@
 
 #include <boost/fiber/detail/config.hpp>
 #include <boost/fiber/detail/notify.hpp>
-#include <boost/fiber/detail/spinlock.hpp>
 #include <boost/fiber/fiber.hpp>
 #include <boost/fiber/algorithm.hpp>
 
@@ -43,7 +42,6 @@ private:
     detail::fiber_base::ptr_t   active_fiber_;
     detail::notify::ptr_t       notifier_;
     wqueue_t                    wqueue_;
-    detail::spinlock            rqueue_mtx_;
     rqueue_t                    rqueue_;
 
 public:
@@ -62,7 +60,7 @@ public:
 
     bool run();
 
-    void wait( unique_lock< detail::spinlock > &);
+    void wait();
 
     void yield();
 
diff --git a/src/condition.cpp b/src/condition.cpp
index 41ef451f..1447f9cd 100644
--- a/src/condition.cpp
+++ b/src/condition.cpp
@@ -20,7 +20,6 @@ namespace boost {
 namespace fibers {
 
 condition::condition() :
-    splk_(),
     waiting_()
 {}
 
@@ -33,12 +32,10 @@ condition::notify_one()
     detail::notify::ptr_t n;
 
     // get one waiting fiber
-    unique_lock< detail::spinlock > lk( splk_);
     if ( ! waiting_.empty() ) {
         n.swap( waiting_.front() );
         waiting_.pop_front();
     }
-    lk.unlock();
 
     // notify waiting fiber
     if ( n)
@@ -51,9 +48,7 @@ condition::notify_all()
     std::deque< detail::notify::ptr_t > waiting;
 
     // get all waiting fibers
-    unique_lock< detail::spinlock > lk( splk_);
     waiting.swap( waiting_);
-    lk.unlock();
 
     // notify all waiting fibers
     while ( ! waiting.empty() )
diff --git a/src/detail/fiber_base.cpp b/src/detail/fiber_base.cpp
index d4872c2e..9673d6c0 100644
--- a/src/detail/fiber_base.cpp
+++ b/src/detail/fiber_base.cpp
@@ -22,11 +22,6 @@ namespace boost {
 namespace fibers {
 namespace detail {
 
-const int fiber_base::READY = 0;
-const int fiber_base::RUNNING = 1;
-const int fiber_base::WAITING = 2;
-const int fiber_base::TERMINATED = 3;
-
 fiber_base::fiber_base( context::fcontext_t * callee, bool preserve_fpu) :
     state_( READY),
     flags_( 0),
@@ -34,7 +29,6 @@ fiber_base::fiber_base( context::fcontext_t * callee, bool preserve_fpu) :
     caller_(),
     callee_( callee),
     except_(),
-    waiting_mtx_(),
     waiting_()
 { if ( preserve_fpu) flags_ |= flag_preserve_fpu; }
 
@@ -72,9 +66,7 @@ fiber_base::release()
     std::vector< ptr_t > waiting;
 
     // get all waiting fibers
-    unique_lock< spinlock > lk( waiting_mtx_);
     waiting.swap( waiting_);
-    lk.unlock();
 
     // notify all waiting fibers
     BOOST_FOREACH( fiber_base::ptr_t p, waiting)
@@ -85,7 +77,6 @@ bool
 fiber_base::join( ptr_t const& p)
 {
     // protect against concurrent access to waiting_
-    unique_lock< spinlock > lk( waiting_mtx_);
     if ( is_terminated() ) return false;
     waiting_.push_back( p);
     return true;
diff --git a/src/detail/spinlock.cpp b/src/detail/spinlock.cpp
deleted file mode 100644
index 30246efe..00000000
--- a/src/detail/spinlock.cpp
+++ /dev/null
@@ -1,44 +0,0 @@
-
-//          Copyright Oliver Kowalke 2009.
-// 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)
-
-#define BOOST_FIBERS_SOURCE
-
-#include <boost/fiber/detail/spinlock.hpp>
-
-#include <boost/assert.hpp>
-
-#include <boost/fiber/detail/scheduler.hpp>
-#include <boost/fiber/detail/thread_yield.hpp>
-
-namespace boost {
-namespace fibers {
-namespace detail {
-
-const int spinlock::LOCKED = 0;
-const int spinlock::UNLOCKED = 1;
-
-spinlock::spinlock() :
-    state_( UNLOCKED)
-{}
-
-void
-spinlock::lock()
-{
-    while ( LOCKED == state_.exchange( LOCKED) )
-    {
-        // busy-wait
-        if ( scheduler::instance().active() )
-            scheduler::instance().yield();
-        else
-            thread_yield();
-    }
-}
-
-void
-spinlock::unlock()
-{ state_ = UNLOCKED; }
-
-}}}
diff --git a/src/mutex.cpp b/src/mutex.cpp
index 44fd464a..93c6b000 100644
--- a/src/mutex.cpp
+++ b/src/mutex.cpp
@@ -22,12 +22,8 @@
 namespace boost {
 namespace fibers {
 
-const int mutex::LOCKED = 0;
-const int mutex::UNLOCKED = 1;
-
 mutex::mutex() :
 	state_( UNLOCKED),
-    splk_(),
     waiting_()
 {}
 
@@ -37,7 +33,7 @@ mutex::~mutex()
 void
 mutex::lock()
 {
-    while ( LOCKED == state_.exchange( LOCKED) )
+    while ( LOCKED == state_)
     {
         detail::notify::ptr_t n( detail::scheduler::instance().active() );
         try
@@ -45,11 +41,10 @@ mutex::lock()
             if ( n)
             {
                 // store this fiber in order to be notified later
-                unique_lock< detail::spinlock > lk( splk_);
                 waiting_.push_back( n);
 
                 // suspend this fiber
-                detail::scheduler::instance().wait( lk);
+                detail::scheduler::instance().wait();
             }
             else
             {
@@ -57,9 +52,7 @@ mutex::lock()
                 n = detail::scheduler::instance().notifier();
 
                 // store this fiber in order to be notified later
-                unique_lock< detail::spinlock > lk( splk_);
                 waiting_.push_back( n);
-                lk.unlock();
 
                 // wait until main-fiber gets notified
                 while ( ! n->is_ready() )
@@ -72,29 +65,34 @@ mutex::lock()
         catch (...)
         {
             // remove fiber from waiting_
-            unique_lock< detail::spinlock > lk( splk_);
             waiting_.erase(
                 std::find( waiting_.begin(), waiting_.end(), n) );
             throw;
         }
     }
+    state_ = LOCKED;
 }
 
 bool
 mutex::try_lock()
-{ return UNLOCKED == state_.exchange( LOCKED); }
+{
+    if ( UNLOCKED == state_)
+    {
+        state_ = LOCKED;
+        return true;
+    }
+    return false;
+}
 
 void
 mutex::unlock()
 {
     detail::notify::ptr_t n;
 
-    unique_lock< detail::spinlock > lk( splk_);
     if ( ! waiting_.empty() ) {
         n.swap( waiting_.front() );
         waiting_.pop_front();
     }
-    lk.unlock();
 
 	state_ = UNLOCKED;
 
diff --git a/src/round_robin.cpp b/src/round_robin.cpp
index b8e3630c..b70943b0 100644
--- a/src/round_robin.cpp
+++ b/src/round_robin.cpp
@@ -34,7 +34,7 @@ namespace detail {
 class main_notifier : public detail::notify
 {
 private:
-    mutable atomic< bool >   ready_;
+    mutable bool   ready_;
 
 public:
     main_notifier() :
@@ -42,7 +42,14 @@ public:
     {}
 
     bool is_ready() const BOOST_NOEXCEPT
-    { return ready_.exchange( false); }
+    {
+        if ( ready_)
+        {
+            ready_ = false;
+            return true;
+        }
+        return false;
+    }
 
     void set_ready() BOOST_NOEXCEPT
     { ready_ = true; }
@@ -54,7 +61,6 @@ round_robin::round_robin() :
     active_fiber_(),
     notifier_( new detail::main_notifier() ),
     wqueue_(),
-    rqueue_mtx_(),
     rqueue_()
 {}
 
@@ -62,7 +68,6 @@ round_robin::~round_robin()
 {
 #if 0
     BOOST_ASSERT( ! active_fiber_);
-    unique_lock< detail::spinlock > lk( rqueue_mtx_);
     BOOST_FOREACH( detail::fiber_base::ptr_t const& p, rqueue_)
     {
         p->release();
@@ -113,10 +118,7 @@ round_robin::run()
         if ( f->interruption_requested() )
             f->set_ready();
         if ( f->is_ready() )
-        {
-            unique_lock< detail::spinlock > lk( rqueue_mtx_);
             rqueue_.push_back( f);
-        }
         else wqueue.push_back( f);
     }
     // exchange local with global waiting queue
@@ -127,11 +129,9 @@ round_robin::run()
     detail::fiber_base::ptr_t f;
     do
     {
-        unique_lock< detail::spinlock > lk( rqueue_mtx_);
         if ( rqueue_.empty() ) return false;
         f.swap( rqueue_.front() );
         rqueue_.pop_front();
-        lk.unlock();
 
         if ( f->is_ready() ) break;
         if ( f->is_waiting() ) wqueue_.push_back( f);
@@ -146,7 +146,7 @@ round_robin::run()
 }
 
 void
-round_robin::wait( unique_lock< detail::spinlock > & lk)
+round_robin::wait()
 {
     BOOST_ASSERT( active_fiber_);
     //FIXME: mabye other threads can change the state of active fiber?
@@ -158,8 +158,6 @@ round_robin::wait( unique_lock< detail::spinlock > & lk)
     wqueue_.push_back( active_fiber_);
     // store active fiber in local var
     detail::fiber_base::ptr_t tmp = active_fiber_;
-    // release lock
-    lk.unlock();
     // suspend fiber
     tmp->suspend();
     // fiber is resumed