Changeset 484

Timestamp:

01/08/11 06:32:57 (14 years ago)

Author:

sean

Message:

Added a comment to core.thread explaining the rationale behind the latest change.

Files:

• trunk/src/core/thread.d (modified) (1 diff)

trunk/src/core/thread.d

@@ -1670 +1670 @@
-    //
-    static void add( Thread t )
-    in
-    {
-        assert( t );
-        assert( !t.next && !t.prev );
-        assert( t.isRunning );
-    }
-    body
-    {
+        // NOTE: This loop is necessary to avoid a race between newly created
+        //       threads and the GC.  If a collection starts between the time
+        //       Thread.start is called and the new thread calls Thread.add,
+        //       the thread could manipulate global state while the collection
+        //       is running, and by being added to the thread list it could be
+        //       resumed by the GC when it was never suspended, which would
+        //       result in an exception thrown by the GC code.  An alternative
+        //       would be to have Thread.start call Thread.add for the new
+        //       thread, but this introduces its own problems, since the
+        //       thread object isn't entirely ready to be operated on by the
+        //       GC.  This could be fixed by tracking thread startup status,
+        //       but it's far easier to simply have Thread.add wait for any
+        //       running collection to stop before altering the thread list.
+        
-        while( true )
-        {
-            synchronized( slock )
-            {
-                if( !suspendDepth )
-                {
-                    if( sm_tbeg )
-                    {
-                        t.next = sm_tbeg;
-                        sm_tbeg.prev = t;