From 2aab2491aacafe4804a8a71970d9b4bd81680c59 Mon Sep 17 00:00:00 2001
From: Ichthyostega <prg@ichthyostega.de>
Date: Fri, 2 Jan 2009 08:02:27 +0100
Subject: [PATCH] deal with a race regarding argument passing

---
 src/lib/thread-wrapper.hpp | 54 +++++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 12 deletions(-)

diff --git a/src/lib/thread-wrapper.hpp b/src/lib/thread-wrapper.hpp
index 8c90295b4..b927f3d51 100644
--- a/src/lib/thread-wrapper.hpp
+++ b/src/lib/thread-wrapper.hpp
@@ -25,27 +25,36 @@
 #define LUMIERA_THREADWRAPPER_H
 
 
-#include "backend/threads.h"
 #include "include/nobugcfg.h"
+#include "lib/sync.hpp"
+
+extern "C" {
+#include "backend/threads.h"
+}
 
 #include <tr1/functional>
 #include <boost/noncopyable.hpp>
 
 
 namespace lumiera {
-
+  
   using std::tr1::bind;
   using std::tr1::function;
   using std::tr1::placeholders::_1;
   
+  using lib::Sync;
+  using lib::NonrecursiveLock_Waitable;
+  
   
   /**
    * A thin convenience wrapper for dealing with threads,
    * as implemented by the backend (on top of pthread).
    * Using this wrapper...
    * - helps with passing data to the function executed in the new thread
-   * - allows to bind to various kinds of functions
+   * - allows to bind to various kinds of functions including member functions
    * - supports integrating with an existing object monitor based lock (planned)
+   * The new thread starts immediately within the ctor; after returning, the new
+   * thread has already copied the arguments and indeed actively started to run.
    * 
    * @note this class is \em not a thread handle. Within Lumiera, we do all of
    *       our thread management such as to avoid using global thread handles.
@@ -56,35 +65,56 @@ namespace lumiera {
    *       was just being shaped. It may well be possible that such a wrapper
    *       is superfluous in the final application. Re-evaluate this!
    */
-  class Thread : boost::noncopyable
+  class Thread
+    : public Sync<NonrecursiveLock_Waitable>,
+      boost::noncopyable
     {
+      volatile bool started_;
+      
       typedef function<void(void)> Operation;
+      Operation const& operation_;
       
       static void
       run (void* arg)
         { 
           ASSERT (arg);
-          Operation doIt_ = *reinterpret_cast<Operation*>(arg);
+          Thread* startingWrapper = reinterpret_cast<Thread*>(arg);
+          Operation _doIt_(startingWrapper->operation_);
+          {
+            Lock sync(startingWrapper);
+            startingWrapper->started_ = true;
+            sync.notify(); // handshake signalling we've gotten the parameter
+          }
           
-          doIt_();
+          _doIt_(); // execute the actual operation in the new thread
         }
       
       
     public:
-      Thread (Literal& purpose, Operation operation, struct nobug_flag *logging_flag = &NOBUG_FLAG(operate))
+      Thread (Literal& purpose, Operation const& operation, struct nobug_flag *logging_flag = &NOBUG_FLAG(operate))
+        : started_(false),
+          operation_(operation)
         {
+          Lock sync(this);
+          LumieraThread res = 
           lumiera_thread_run ( LUMIERA_THREAD_INTERACTIVE
                              , &run         // invoking the run helper and..
-                             , &operation   // passing the actual operation as parameter
+                             , this         // passing this start context as parameter
                              , 0            // no condition variable provided (for now...)
                              , purpose.c_str()
                              , logging_flag
                              );
+          
+          if (!res)
+            throw error::State("failed to create new thread.");
+          
+          // make sure the new thread had the opportunity to take the Operation
+          // prior to leaving and thereby possibly destroying this local context
+          sync.wait (started_);
         }
     };
-    
   
-
-   
-} // namespace lumiera
+  
+  
+ } // namespace lumiera
 #endif