[Boost-commit] svn:boost r57882 - trunk/boost/thread/win32

Subject: [Boost-commit] svn:boost r57882 - trunk/boost/thread/win32
From: anthony_at_[hidden]
Date: 2009-11-24 04:59:21

Author: anthonyw
Date: 2009-11-24 04:59:21 EST (Tue, 24 Nov 2009)
New Revision: 57882
URL: http://svn.boost.org/trac/boost/changeset/57882

Log:
Only allocate an event if there is contention in call_once
Text files modified: 
   trunk/boost/thread/win32/once.hpp |   168 +++++++++++++++++++++------------------ 
   1 files changed, 92 insertions(+), 76 deletions(-)

Modified: trunk/boost/thread/win32/once.hpp
==============================================================================
--- trunk/boost/thread/win32/once.hpp	(original)
+++ trunk/boost/thread/win32/once.hpp	2009-11-24 04:59:21 EST (Tue, 24 Nov 2009)
@@ -30,81 +30,33 @@
 
 namespace boost
 {
-    typedef long once_flag;
+    struct once_flag
+    {
+        long status;
+        long count;
+        long throw_count;
+        void* event_handle;
+    };
 
-#define BOOST_ONCE_INIT 0
+#define BOOST_ONCE_INIT {0,0,0,0}
 
     namespace detail
     {
-        struct win32_mutex_scoped_lock
-        {
-            void* const mutex_handle;
-            explicit win32_mutex_scoped_lock(void* mutex_handle_):
-                mutex_handle(mutex_handle_)
-            {
-                BOOST_VERIFY(!win32::WaitForSingleObject(mutex_handle,win32::infinite));
-            }
-            ~win32_mutex_scoped_lock()
-            {
-                BOOST_VERIFY(win32::ReleaseMutex(mutex_handle)!=0);
-            }
-        private:
-            void operator=(win32_mutex_scoped_lock&);
-        };
-
-#ifdef BOOST_NO_ANSI_APIS
-        template <class I>
-        void int_to_string(I p, wchar_t* buf)
-        {
-            for(unsigned i=0; i < sizeof(I)*2; ++i,++buf)
-            {
-                *buf = L'A' + static_cast<wchar_t>((p >> (i*4)) & 0x0f);
-            }
-            *buf = 0;
-        }
-#else
-        template <class I>
-        void int_to_string(I p, char* buf)
+        inline void* allocate_event_handle(void*& handle)
         {
-            for(unsigned i=0; i < sizeof(I)*2; ++i,++buf)
+            void* const new_handle=::boost::detail::win32::create_anonymous_event(
+                ::boost::detail::win32::manual_reset_event,
+                ::boost::detail::win32::event_initially_reset);
+            
+            void* event_handle=BOOST_INTERLOCKED_COMPARE_EXCHANGE_POINTER(&handle,
+                                                                          new_handle,0);
+            if(event_handle)
             {
-                *buf = 'A' + static_cast<char>((p >> (i*4)) & 0x0f);
+                ::boost::detail::win32::CloseHandle(new_handle);
+                return event_handle;
             }
-            *buf = 0;
+            return new_handle;
         }
-#endif
-
-        // create a named mutex. It doesn't really matter what this name is
-        // as long as it is unique both to this process, and to the address of "flag":
-        inline void* create_once_mutex(void* flag_address)
-        {
-        
-#ifdef BOOST_NO_ANSI_APIS
-            typedef wchar_t char_type;
-            static const char_type fixed_mutex_name[]=L"{C15730E2-145C-4c5e-B005-3BC753F42475}-once-flag";
-#else
-            typedef char char_type;
-            static const char_type fixed_mutex_name[]="{C15730E2-145C-4c5e-B005-3BC753F42475}-once-flag";
-#endif
-            unsigned const once_mutex_name_fixed_buffer_size=sizeof(fixed_mutex_name)/sizeof(char_type);
-            unsigned const once_mutex_name_fixed_length=once_mutex_name_fixed_buffer_size-1;
-            unsigned const once_mutex_name_length=once_mutex_name_fixed_buffer_size+sizeof(void*)*2+sizeof(unsigned long)*2;
-            char_type mutex_name[once_mutex_name_length];
-            
-            std::memcpy(mutex_name,fixed_mutex_name,sizeof(fixed_mutex_name));
-
-            BOOST_STATIC_ASSERT(sizeof(void*) == sizeof(std::ptrdiff_t));
-            detail::int_to_string(reinterpret_cast<std::ptrdiff_t>(flag_address), mutex_name + once_mutex_name_fixed_length);
-            detail::int_to_string(win32::GetCurrentProcessId(), mutex_name + once_mutex_name_fixed_length + sizeof(void*)*2);
-
-#ifdef BOOST_NO_ANSI_APIS
-            return win32::CreateMutexW(0, 0, mutex_name);
-#else
-            return win32::CreateMutexA(0, 0, mutex_name);
-#endif
-        }
-
-        
     }
     
 
@@ -114,20 +66,84 @@
         // Try for a quick win: if the procedure has already been called
         // just skip through:
         long const function_complete_flag_value=0xc15730e2;
+        long const running_value=0x7f0725e3;
+        long status;
+        bool counted=false;
+        void* event_handle=0;
+        long throw_count=0;
 
-        if(::boost::detail::interlocked_read_acquire(&flag)!=function_complete_flag_value)
+        while((status=::boost::detail::interlocked_read_acquire(&flag.status))
+              !=function_complete_flag_value)
         {
-            void* const mutex_handle(::boost::detail::create_once_mutex(&flag));
-            BOOST_ASSERT(mutex_handle);
-            detail::win32::handle_manager const closer(mutex_handle);
-            detail::win32_mutex_scoped_lock const lock(mutex_handle);
-      
-            if(flag!=function_complete_flag_value)
+            status=BOOST_INTERLOCKED_COMPARE_EXCHANGE(&flag.status,running_value,0);
+            if(!status)
             {
-                f();
-                BOOST_INTERLOCKED_EXCHANGE(&flag,function_complete_flag_value);
+                try
+                {
+                    f();
+                    if(!counted)
+                    {
+                        BOOST_INTERLOCKED_INCREMENT(&flag.count);
+                        counted=true;
+                    }
+                    BOOST_INTERLOCKED_EXCHANGE(&flag.status,function_complete_flag_value);
+                    if(!event_handle && 
+                       (::boost::detail::interlocked_read_acquire(&flag.count)>1))
+                    {
+                        event_handle=::boost::detail::allocate_event_handle(flag.event_handle);
+                    }
+                    if(event_handle)
+                    {
+                        ::boost::detail::win32::SetEvent(event_handle);
+                    }
+                    throw_count=::boost::detail::interlocked_read_acquire(&flag.throw_count);
+                    break;
+                }
+                catch(...)
+                {
+                    if(counted)
+                    {
+                        BOOST_INTERLOCKED_INCREMENT(&flag.throw_count);
+                    }
+                    BOOST_INTERLOCKED_EXCHANGE(&flag.status,0);
+                    throw;
+                }
             }
+
+            if(!counted)
+            {
+                BOOST_INTERLOCKED_INCREMENT(&flag.count);
+                counted=true;
+                status=::boost::detail::interlocked_read_acquire(&flag.status);
+                if(status==function_complete_flag_value)
+                {
+                    break;
+                }
+                event_handle=::boost::detail::interlocked_read_acquire(&flag.event_handle);
+                if(!event_handle)
+                {
+                    event_handle=::boost::detail::allocate_event_handle(flag.event_handle);
+                    continue;
+                }
+            }
+            
         }
+        if(counted || throw_count)
+        {
+            if(!BOOST_INTERLOCKED_EXCHANGE_ADD(&flag.count,(counted?1:0)+throw_count))
+            {
+                if(!event_handle)
+                {
+                    event_handle=::boost::detail::interlocked_read_acquire(&flag.event_handle);
+                }
+                if(event_handle)
+                {
+                    BOOST_INTERLOCKED_EXCHANGE_POINTER(&flag.event_handle,0);
+                    ::boost::detail::win32::CloseHandle(event_handle);
+                }
+            }
+        }
+        
     }
 }