mca/base: revive mca_base_component_repository_retain_component

This commit revives the component retention functionality that was
removed as part of the component repository rewrite. The new
mca_base_component_repository_retain_component function works by
preventing the dlclosing of a dynamic component until a matching call
to mca_base_component_repository_release is made.

Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>

opal/mca/base/mca_base_component_repository.c

@@ -280,30 +280,57 @@ static void mca_base_component_repository_release_internal (mca_base_component_r
 }
 #endif
 
-void mca_base_component_repository_release(const mca_base_component_t *component)
-{
 #if OPAL_HAVE_DL_SUPPORT
+static mca_base_component_repository_item_t *find_component (const char *type, const char *name)
+{
     mca_base_component_repository_item_t *ri;
     opal_list_t *component_list;
     int ret;
 
-    ret = opal_hash_table_get_value_ptr (&mca_base_component_repository, component->mca_type_name,
-                                         strlen (component->mca_type_name), (void **) &component_list);
+    ret = opal_hash_table_get_value_ptr (&mca_base_component_repository, type,
+                                         strlen (type), (void **) &component_list);
     if (OPAL_SUCCESS != ret) {
         /* component does not exist in the repository */
-        return;
+        return NULL;
     }
 
     OPAL_LIST_FOREACH(ri, component_list, mca_base_component_repository_item_t) {
-        if (0 == strcmp (ri->ri_name, component->mca_component_name)) {
-            /* go ahead and dlclose the component if it is open */
-            mca_base_component_repository_release_internal (ri);
-            break;
+        if (0 == strcmp (ri->ri_name, name)) {
+            return ri;
         }
     }
+
+    return NULL;
+}
+#endif
+
+void mca_base_component_repository_release(const mca_base_component_t *component)
+{
+#if OPAL_HAVE_DL_SUPPORT
+    mca_base_component_repository_item_t *ri;
+
+    ri = find_component (component->mca_type_name, component->mca_component_name);
+    if (NULL != ri && !(--ri->ri_refcnt)) {
+        mca_base_component_repository_release_internal (ri);
+    }
 #endif
 }
 
+int mca_base_component_repository_retain_component (const char *type, const char *name)
+{
+#if OPAL_HAVE_DL_SUPPORT
+    mca_base_component_repository_item_t *ri = find_component(type, name);
+
+    if (NULL != ri) {
+        ++ri->ri_refcnt;
+        return OPAL_SUCCESS;
+    }
+
+    return OPAL_ERR_NOT_FOUND;
+#else
+    return OPAL_ERR_NOT_SUPPORTED;
+#endif
+}
 
 int mca_base_component_repository_open (mca_base_framework_t *framework,
                                         mca_base_component_repository_item_t *ri)
@@ -443,6 +470,7 @@ int mca_base_component_repository_open (mca_base_framework_t *framework,
            component to be closed later. */
 
         ri->ri_component_struct = mitem->cli_component = component_struct;
+        ri->ri_refcnt = 1;
         opal_list_append(&framework->framework_components, &mitem->super);
 
         opal_output_verbose (MCA_BASE_VERBOSE_INFO, 0, "mca_base_component_repository_open: opened dynamic %s MCA "

opal/mca/base/mca_base_component_repository.h

@@ -1,3 +1,4 @@
+/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
@@ -10,6 +11,8 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2015 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2015      Los Alamos National Security, LLC. All rights
+ *                         reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -50,6 +53,8 @@ struct mca_base_component_repository_item_t {
 
     opal_dl_handle_t *ri_dlhandle;
     const mca_base_component_t *ri_component_struct;
+
+    int ri_refcnt;
 };
 typedef struct mca_base_component_repository_item_t mca_base_component_repository_item_t;
 
@@ -102,7 +107,25 @@ int mca_base_component_repository_open (mca_base_framework_t *framework,
                                         mca_base_component_repository_item_t *ri);
 
 
-void mca_base_component_repository_release(const mca_base_component_t *component);
+/**
+ * @brief Reduce the reference count of a component and dlclose it if necessary
+ */
+void mca_base_component_repository_release (const mca_base_component_t *component);
+
+/**
+ * @brief Increase the reference count of a component
+ *
+ * Each component repository item starts with a reference count of 0. This ensures that
+ * when a framework closes it's components the repository items are all correctly
+ * dlclosed. This function can be used to prevent the dlclose if a component is needed
+ * after its framework has closed the associated component. Users of this function
+ * should call mca_base_component_repository_release() once they are finished with the
+ * component.
+ *
+ * @note all components are automatically unloaded by the
+ * mca_base_component_repository_finalize() call.
+ */
+int mca_base_component_repository_retain_component (const char *type, const char *name);
 
 END_C_DECLS