Windows improvements : manual backport of

htttp://lists.mysql.com/commits/50957?f=plain
      
Always use TLS functions instead of __declspec(thread) to access 
thread local storage variables.
The change removes the necessity to recomplile the same source
files twice -  with USE_TLS for DLLs and without USE_TLS for EXEs.
Real benefit of this change is better readability and maintainability
of TLS functions within MySQL.
              
There is a performance loss using TlsXXX functions compared to __declspec 
but the difference is negligible in practice. In a sysbench-like benchmark 
I ran with with TlsGetValue, pthread_[get|set]_specific was called 600000000 
times and took 0.17sec of total 35min CPU time, or 0.008%.

2 files changed, 0 insertions, 28 deletions

diff --git a/mysys/my_thr_init.c b/mysys/my_thr_init.c
index 2278c467f32..2c346145cf5 100644
--- a/mysys/my_thr_init.c
+++ b/mysys/my_thr_init.c
@@ -23,11 +23,7 @@
 #include <signal.h>
 
 #ifdef THREAD
-#ifdef USE_TLS
 pthread_key(struct st_my_thread_var*, THR_KEY_mysys);
-#else
-pthread_key(struct st_my_thread_var, THR_KEY_mysys);
-#endif /* USE_TLS */
 pthread_mutex_t THR_LOCK_malloc,THR_LOCK_open,
 	        THR_LOCK_lock,THR_LOCK_isam,THR_LOCK_myisam,THR_LOCK_heap,
                 THR_LOCK_net, THR_LOCK_charset, THR_LOCK_threads, THR_LOCK_time;
@@ -258,7 +254,6 @@ my_bool my_thread_init(void)
           (ulong) pthread_self());
 #endif  
 
-#if !defined(__WIN__) || defined(USE_TLS)
   if (my_pthread_getspecific(struct st_my_thread_var *,THR_KEY_mysys))
   {
 #ifdef EXTRA_DEBUG_THREADS
@@ -273,15 +268,6 @@ my_bool my_thread_init(void)
     goto end;
   }
   pthread_setspecific(THR_KEY_mysys,tmp);
-
-#else /* defined(__WIN__) && !(defined(USE_TLS) */
-  /*
-    Skip initialization if the thread specific variable is already initialized
-  */
-  if (THR_KEY_mysys.id)
-    goto end;
-  tmp= &THR_KEY_mysys;
-#endif
 #if defined(__WIN__) && defined(EMBEDDED_LIBRARY)
   tmp->pthread_self= (pthread_t) getpid();
 #else
@@ -342,11 +328,7 @@ void my_thread_end(void)
     pthread_cond_destroy(&tmp->suspend);
 #endif
     pthread_mutex_destroy(&tmp->mutex);
-#if !defined(__WIN__) || defined(USE_TLS)
     free(tmp);
-#else
-    tmp->init= 0;
-#endif
 
     /*
       Decrement counter for number of running threads. We are using this
@@ -360,10 +342,7 @@ void my_thread_end(void)
       pthread_cond_signal(&THR_COND_threads);
    pthread_mutex_unlock(&THR_LOCK_threads);
   }
-  /* The following free has to be done, even if my_thread_var() is 0 */
-#if !defined(__WIN__) || defined(USE_TLS)
   pthread_setspecific(THR_KEY_mysys,0);
-#endif
 }
 
 struct st_my_thread_var *_my_thread_var(void)
diff --git a/mysys/my_winthread.c b/mysys/my_winthread.c
index e94369bec32..543e1787fb6 100644
--- a/mysys/my_winthread.c
+++ b/mysys/my_winthread.c
@@ -129,12 +129,5 @@ void pthread_exit(void *a)
   _endthread();
 }
 
-/* This is neaded to get the macro pthread_setspecific to work */
-
-int win_pthread_setspecific(void *a,void *b,uint length)
-{
-  memcpy(a,b,length);
-  return 0;
-}
 
 #endif