From 140dce7614371cb8885ca03308c1803cd04632e6 Mon Sep 17 00:00:00 2001
From: Gleb Natapov <gleb@voltaire.com>
Date: Tue, 11 Sep 2007 15:40:30 +0000
Subject: [PATCH] Fix ABA problem in atomic_lifo code. This is temporary
 solution for now. We are looking for a better one.

This commit was SVN r16091.
---
 opal/class/opal_atomic_lifo.h | 14 ++++++++++----
 opal/class/opal_list.c        |  2 ++
 opal/class/opal_list.h        |  2 ++
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/opal/class/opal_atomic_lifo.h b/opal/class/opal_atomic_lifo.h
index caf35b10a0..25aa26fbc3 100644
--- a/opal/class/opal_atomic_lifo.h
+++ b/opal/class/opal_atomic_lifo.h
@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2007      Voltaire All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -71,8 +72,10 @@ static inline opal_list_item_t* opal_atomic_lifo_push( opal_atomic_lifo_t* lifo,
         item->opal_list_next = lifo->opal_lifo_head;
         if( opal_atomic_cmpset_ptr( &(lifo->opal_lifo_head),
                                     (void*)item->opal_list_next,
-                                    item ) )
+                                    item ) ) {
+            opal_atomic_cmpset_32((volatile int32_t*)&item->item_free, 1, 0);
             return (opal_list_item_t*)item->opal_list_next;
+        }
         /* DO some kind of pause to release the bus */
     } while( 1 );
 #else
@@ -89,14 +92,17 @@ static inline opal_list_item_t* opal_atomic_lifo_pop( opal_atomic_lifo_t* lifo )
 {
     opal_list_item_t* item;
 #if OMPI_HAVE_THREAD_SUPPORT
-    do {
-        item = lifo->opal_lifo_head;
+    while((item = lifo->opal_lifo_head) != &(lifo->opal_lifo_ghost))
+    {
+        if(!opal_atomic_cmpset_32((volatile int32_t*)&item->item_free, 0, 1))
+            continue;
         if( opal_atomic_cmpset_ptr( &(lifo->opal_lifo_head),
                                     item,
                                     (void*)item->opal_list_next ) )
             break;
+        opal_atomic_cmpset_32((volatile int32_t*)&item->item_free, 1, 0);
         /* Do some kind of pause to release the bus */
-    } while( 1 );
+    } 
 #else
     item = lifo->opal_lifo_head;
     lifo->opal_lifo_head = (opal_list_item_t*)item->opal_list_next;
diff --git a/opal/class/opal_list.c b/opal/class/opal_list.c
index c8a5568165..7231c5338c 100644
--- a/opal/class/opal_list.c
+++ b/opal/class/opal_list.c
@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2007      Voltaire All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -55,6 +56,7 @@ OBJ_CLASS_INSTANCE(
 static void opal_list_item_construct(opal_list_item_t *item)
 {
     item->opal_list_next = item->opal_list_prev = NULL;
+    item->item_free = 1;
 #if OMPI_ENABLE_DEBUG
     item->opal_list_item_refcount = 0;
     item->opal_list_item_belong_to = NULL;
diff --git a/opal/class/opal_list.h b/opal/class/opal_list.h
index 83fa57ba68..ea9b327198 100644
--- a/opal/class/opal_list.h
+++ b/opal/class/opal_list.h
@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2007      Voltaire All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -102,6 +103,7 @@ struct opal_list_item_t
     /**< Pointer to next list item */
     volatile struct opal_list_item_t *opal_list_prev;
     /**< Pointer to previous list item */
+    int32_t item_free;
 
 #if OMPI_ENABLE_DEBUG
     /** Atomic reference count for debugging */