pthread_once non conformant

[Jerome Souquieres <jerome.souquieres@gmail.com>]

Hi,

I think I've spotted a bug in pthread_once (in ecos v3.0). The current
implementation does not enforce the part of the specification that
says: "On return from pthread_once(), it is guaranteed that
init_routine() has completed".

Here is a proposal for a patch, I did not post it to ecos-patches
because I currently don't have a working eCos target to test this.


--- pthread.cxx	2009-01-29 18:47:52.000000000 +0100
+++ pthread-fixonce.cxx	2009-11-01 21:07:42.639875000 +0100
@@ -1328,22 +1328,23 @@ externC int pthread_once (pthread_once_t
     PTHREAD_ENTRY();

     PTHREAD_CHECK( once_control );
     PTHREAD_CHECK( init_routine );

-    pthread_once_t old;
-
-    // Do a test and set on the once_control object.
     pthread_mutex.lock();

-    old = *once_control;
-    *once_control = 1;
+    // If the once_control is zero, call the init_routine().
+    // the mutex must stay locked during init_routine because
+    // concurrent threads must be blocked until init_routine has
+    // done its business
+    if ( !*once_control )
+    {
+        init_routine();
+        *once_control = 1;
+    }

     pthread_mutex.unlock();
-
-    // If the once_control was zero, call the init_routine().
-    if( !old ) init_routine();

     PTHREAD_RETURN(0);
 }