pmix2x/class: correctly handle concurrent class initialization

(back-ported from upstream commit pmix/master@ceedbd67fd)

Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>

opal/mca/pmix/pmix2x/pmix/src/class/pmix_object.c

@@ -10,6 +10,8 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2014-2016 Intel, Inc.  All rights reserved.
+ * Copyright (c) 2016      Research Organization for Information Science
+ *                         and Technology (RIST). All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -28,6 +30,7 @@
 
 
 #include <stdio.h>
+#include <pthread.h>
 
 #include "src/class/pmix_object.h"
 
@@ -48,9 +51,12 @@ pmix_class_t pmix_object_t_class = {
     sizeof(pmix_object_t) /* size of the pmix object */
 };
 
+int pmix_class_init_epoch = 1;
+
 /*
  * Local variables
  */
+static pthread_mutex_t class_mutex = PTHREAD_MUTEX_INITIALIZER;
 static void** classes = NULL;
 static int num_classes = 0;
 static int max_classes = 0;
@@ -81,7 +87,17 @@ void pmix_class_initialize(pmix_class_t *cls)
     /* Check to see if anyone initialized
        this class before we got a chance to */
 
-    if (1 == cls->cls_initialized) {
+    if (pmix_class_init_epoch == cls->cls_initialized) {
+        return;
+    }
+    pthread_mutex_lock(&class_mutex);
+
+    /* If another thread initializing this same class came in at
+       roughly the same time, it may have gotten the lock and
+       initialized.  So check again. */
+
+    if (pmix_class_init_epoch == cls->cls_initialized) {
+        pthread_mutex_unlock(&class_mutex);
         return;
     }
 
@@ -141,10 +157,12 @@ void pmix_class_initialize(pmix_class_t *cls)
     }
     *cls_destruct_array = NULL;  /* end marker for the destructors */
 
-    cls->cls_initialized = 1;
+    cls->cls_initialized = pmix_class_init_epoch;
     save_class(cls);
 
     /* All done */
+
+    pthread_mutex_unlock(&class_mutex);
 }
 
 
@@ -155,6 +173,12 @@ int pmix_class_finalize(void)
 {
     int i;
 
+    if (INT_MAX == pmix_class_init_epoch) {
+        pmix_class_init_epoch = 1;
+    } else {
+        pmix_class_init_epoch++;
+    }
+
     if (NULL != classes) {
         for (i = 0; i < num_classes; ++i) {
             if (NULL != classes[i]) {

opal/mca/pmix/pmix2x/pmix/src/class/pmix_object.h

@@ -12,6 +12,8 @@
  *                         All rights reserved.
  * Copyright (c) 2007      Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2013-2016 Intel, Inc.  All rights reserved.
+ * Copyright (c) 2016      Research Organization for Information Science
+ *                         and Technology (RIST). All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -163,6 +165,8 @@ struct pmix_class_t {
     size_t cls_sizeof;              /**< size of an object instance */
 };
 
+extern int pmix_class_init_epoch;
+
 /**
  * For static initializations of OBJects.
  *
@@ -347,7 +351,7 @@ do {                                                            \
 #define PMIX_CONSTRUCT_INTERNAL(object, type)                        \
 do {                                                                \
     PMIX_SET_MAGIC_ID((object), PMIX_OBJ_MAGIC_ID);              \
-    if (0 == (type)->cls_initialized) {                             \
+    if (pmix_class_init_epoch != (type)->cls_initialized) {                             \
         pmix_class_initialize((type));                              \
     }                                                               \
     ((pmix_object_t *) (object))->obj_class = (type);               \
@@ -467,7 +471,7 @@ static inline pmix_object_t *pmix_obj_new(pmix_class_t * cls)
     assert(cls->cls_sizeof >= sizeof(pmix_object_t));
 
     object = (pmix_object_t *) malloc(cls->cls_sizeof);
-    if (0 == cls->cls_initialized) {
+    if (pmix_class_init_epoch != cls->cls_initialized) {
         pmix_class_initialize(cls);
     }
     if (NULL != object) {