The code tries to prevent itself from running for more then one communicator

simultaneously, but is doing it incorrectly. If the function is running already
for one communicator and it is called from another thread for other communicator
with lower cid the check comm->c_contextid != ompi_comm_lowest_cid()
will fail and the function will be executed for two different communicators by
two threads simultaneously. There is nothing in the algorithm that prevent it
from been running simultaneously for different communicators as far as I can see,
but ompi_comm_unregister_cid() assumes that it is always called for a communicator
with the lowest cid and this is not always the case. This patch removes bogus
lowest cid check and fix ompi_comm_register_cid() to properly remove cid from
the list.

This commit was SVN r16088.

ompi/communicator/comm_cid.c

@@ -11,6 +11,7 @@
  *                         All rights reserved.
  * Copyright (c) 2006-2007 University of Houston. All rights reserved.
  * Copyright (c) 2007      Cisco, Inc.  All rights reserved.
+ * Copyright (c) 2007      Voltaire All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -170,15 +171,6 @@ int ompi_comm_nextcid ( ompi_communicator_t* newcomm,
              * This is the real algorithm described in the doc 
              */
             
-            OPAL_THREAD_LOCK(&ompi_cid_lock);
-            if (comm->c_contextid != ompi_comm_lowest_cid() ) {
-                /* if not lowest cid, we do not continue, but sleep and try again */
-                OPAL_THREAD_UNLOCK(&ompi_cid_lock);
-                continue;
-            }
-            OPAL_THREAD_UNLOCK(&ompi_cid_lock);
-            
-            
             for (i=start; i < mca_pml.pml_max_contextid ; i++) {
                 flag=ompi_pointer_array_test_and_set_item(&ompi_mpi_communicators, 
                                                           i, comm);
@@ -365,10 +357,18 @@ static int ompi_comm_register_cid (uint32_t cid )
 
 static int ompi_comm_unregister_cid (uint32_t cid)
 {
-    ompi_comm_reg_t *regcom=NULL;
-    opal_list_item_t *item=opal_list_remove_first(&ompi_registered_comms);
+    ompi_comm_reg_t *regcom;
+    opal_list_item_t *item;
 
-    regcom = (ompi_comm_reg_t *) item;
+    for (item = opal_list_get_first(&ompi_registered_comms);
+         item != opal_list_get_end(&ompi_registered_comms);
+         item = opal_list_get_next(item)) {
+        regcom = (ompi_comm_reg_t *)item;
+        if(regcom->cid == cid) {
+            opal_list_remove_item(&ompi_registered_comms, item);
+            break;
+        }
+    }
     OBJ_RELEASE(regcom);
     return OMPI_SUCCESS;
 }