Remove need to have a mutex per idle thread.

asio/include/asio/detail/null_event.hpp

@@ -43,17 +43,20 @@ public:
   }
 
   // Signal the event.
-  void signal()
+  template <typename Lock>
+  void signal(Lock&)
   {
   }
 
   // Reset the event.
-  void clear()
+  template <typename Lock>
+  void clear(Lock&)
   {
   }
 
   // Wait for the event to become signalled.
-  void wait()
+  template <typename Lock>
+  void wait(Lock&)
   {
   }
 };

asio/include/asio/detail/posix_event.hpp

@@ -24,6 +24,7 @@
 #if defined(BOOST_HAS_PTHREADS)
 
 #include "asio/detail/push_options.hpp"
+#include <boost/assert.hpp>
 #include <boost/throw_exception.hpp>
 #include <pthread.h>
 #include "asio/detail/pop_options.hpp"
@@ -42,7 +43,7 @@ public:
   posix_event()
     : signalled_(false)
   {
-    int error = ::pthread_mutex_init(&mutex_, 0);
+    int error = ::pthread_cond_init(&cond_, 0);
     if (error != 0)
     {
       asio::system_error e(
@@ -50,53 +51,43 @@ public:
           "event");
       boost::throw_exception(e);
     }
-
-    error = ::pthread_cond_init(&cond_, 0);
-    if (error != 0)
-    {
-      ::pthread_mutex_destroy(&mutex_);
-      asio::system_error e(
-          asio::error_code(error, asio::native_ecat),
-          "event");
-      boost::throw_exception(e);
-    }
   }
 
   // Destructor.
   ~posix_event()
   {
     ::pthread_cond_destroy(&cond_);
-    ::pthread_mutex_destroy(&mutex_);
   }
 
   // Signal the event.
-  void signal()
+  template <typename Lock>
+  void signal(Lock& lock)
   {
-    ::pthread_mutex_lock(&mutex_); // Ignore EINVAL and EDEADLK.
+    BOOST_ASSERT(lock.locked());
+    (void)lock;
     signalled_ = true;
     ::pthread_cond_signal(&cond_); // Ignore EINVAL.
-    ::pthread_mutex_unlock(&mutex_); // Ignore EINVAL and EPERM.
   }
 
   // Reset the event.
-  void clear()
+  template <typename Lock>
+  void clear(Lock& lock)
   {
-    ::pthread_mutex_lock(&mutex_); // Ignore EINVAL and EDEADLK.
+    BOOST_ASSERT(lock.locked());
+    (void)lock;
     signalled_ = false;
-    ::pthread_mutex_unlock(&mutex_); // Ignore EINVAL and EPERM.
   }
 
   // Wait for the event to become signalled.
-  void wait()
+  template <typename Lock>
+  void wait(Lock& lock)
   {
-    ::pthread_mutex_lock(&mutex_); // Ignore EINVAL and EDEADLK.
+    BOOST_ASSERT(lock.locked());
     while (!signalled_)
-      ::pthread_cond_wait(&cond_, &mutex_); // Ignore EINVAL.
+      ::pthread_cond_wait(&cond_, &lock.mutex().mutex_); // Ignore EINVAL.
-    ::pthread_mutex_unlock(&mutex_); // Ignore EINVAL and EPERM.
   }
 
 private:
-  ::pthread_mutex_t mutex_;
   ::pthread_cond_t cond_;
   bool signalled_;
 };

asio/include/asio/detail/posix_mutex.hpp

@@ -35,6 +35,8 @@
 namespace asio {
 namespace detail {
 
+class posix_event;
+
 class posix_mutex
   : private noncopyable
 {
@@ -87,6 +89,7 @@ public:
   }
 
 private:
+  friend class posix_event;
   ::pthread_mutex_t mutex_;
 };
 

asio/include/asio/detail/scoped_lock.hpp

@@ -63,6 +63,18 @@ public:
     }
   }
 
+  // Test whether the lock is held.
+  bool locked() const
+  {
+    return locked_;
+  }
+
+  // Get the underlying mutex.
+  Mutex& mutex()
+  {
+    return mutex_;
+  }
+
 private:
   // The underlying mutex.
   Mutex& mutex_;

asio/include/asio/detail/task_io_service.hpp

@@ -132,7 +132,7 @@ public:
   void stop()
   {
     asio::detail::mutex::scoped_lock lock(mutex_);
-    stop_all_threads();
+    stop_all_threads(lock);
   }
 
   // Reset in preparation for a subsequent run invocation.
@@ -154,7 +154,7 @@ public:
   {
     asio::detail::mutex::scoped_lock lock(mutex_);
     if (--outstanding_work_ == 0)
-      stop_all_threads();
+      stop_all_threads(lock);
   }
 
   // Request invocation of the given handler.
@@ -199,7 +199,7 @@ public:
     ++outstanding_work_;
 
     // Wake up a thread to execute the handler.
-    if (!interrupt_one_idle_thread())
+    if (!interrupt_one_idle_thread(lock))
       if (task_handler_.next_ == 0 && handler_queue_end_ != &task_handler_)
         task_.interrupt();
   }
@@ -212,7 +212,7 @@ private:
   {
     if (outstanding_work_ == 0 && !stopped_)
     {
-      stop_all_threads();
+      stop_all_threads(lock);
       ec = asio::error_code();
       return 0;
     }
@@ -267,10 +267,8 @@ private:
         // Nothing to run right now, so just wait for work to do.
         this_idle_thread->next = first_idle_thread_;
         first_idle_thread_ = this_idle_thread;
-        this_idle_thread->wakeup_event.clear();
+        this_idle_thread->wakeup_event.clear(lock);
-        lock.unlock();
+        this_idle_thread->wakeup_event.wait(lock);
-        this_idle_thread->wakeup_event.wait();
-        lock.lock();
       }
       else
       {
@@ -284,38 +282,41 @@ private:
   }
 
   // Stop the task and all idle threads.
-  void stop_all_threads()
+  void stop_all_threads(
+      asio::detail::mutex::scoped_lock& lock)
   {
     stopped_ = true;
-    interrupt_all_idle_threads();
+    interrupt_all_idle_threads(lock);
     if (task_handler_.next_ == 0 && handler_queue_end_ != &task_handler_)
       task_.interrupt();
   }
 
   // Interrupt a single idle thread. Returns true if a thread was interrupted,
   // false if no running thread could be found to interrupt.
-  bool interrupt_one_idle_thread()
+  bool interrupt_one_idle_thread(
+      asio::detail::mutex::scoped_lock& lock)
   {
     if (first_idle_thread_)
     {
       idle_thread_info* idle_thread = first_idle_thread_;
       first_idle_thread_ = idle_thread->next;
       idle_thread->next = 0;
-      idle_thread->wakeup_event.signal();
+      idle_thread->wakeup_event.signal(lock);
       return true;
     }
     return false;
   }
 
   // Interrupt all idle threads.
-  void interrupt_all_idle_threads()
+  void interrupt_all_idle_threads(
+      asio::detail::mutex::scoped_lock& lock)
   {
     while (first_idle_thread_)
     {
       idle_thread_info* idle_thread = first_idle_thread_;
       first_idle_thread_ = idle_thread->next;
       idle_thread->next = 0;
-      idle_thread->wakeup_event.signal();
+      idle_thread->wakeup_event.signal(lock);
     }
   }
 
@@ -459,7 +460,7 @@ private:
     {
       lock_.lock();
       if (--task_io_service_.outstanding_work_ == 0)
-        task_io_service_.stop_all_threads();
+        task_io_service_.stop_all_threads(lock_);
     }
 
   private:

asio/include/asio/detail/win_event.hpp

@@ -28,6 +28,7 @@
 #include "asio/detail/socket_types.hpp"
 
 #include "asio/detail/push_options.hpp"
+#include <boost/assert.hpp>
 #include <boost/throw_exception.hpp>
 #include "asio/detail/pop_options.hpp"
 
@@ -59,21 +60,31 @@ public:
   }
 
   // Signal the event.
-  void signal()
+  template <typename Lock>
+  void signal(Lock& lock)
   {
+    BOOST_ASSERT(lock.locked());
+    (void)lock;
     ::SetEvent(event_);
   }
 
   // Reset the event.
-  void clear()
+  template <typename Lock>
+  void clear(Lock& lock)
   {
+    BOOST_ASSERT(lock.locked());
+    (void)lock;
     ::ResetEvent(event_);
   }
 
   // Wait for the event to become signalled.
-  void wait()
+  template <typename Lock>
+  void wait(Lock& lock)
   {
+    BOOST_ASSERT(lock.locked());
+    lock.unlock();
     ::WaitForSingleObject(event_, INFINITE);
+    lock.lock();
   }
 
 private: