rcache/udreg: make reference count thread safe

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

opal/mca/rcache/udreg/rcache_udreg_module.c

@@ -301,7 +301,7 @@ static int mca_rcache_udreg_register(mca_rcache_base_module_t *rcache, void *add
     OPAL_THREAD_UNLOCK(&rcache_udreg->lock);
 
     *reg = udreg_reg;
-    ++udreg_reg->ref_count;
+    (void) OPAL_THREAD_ADD32(&udreg_reg->ref_count, 1);
     udreg_reg->rcache_context = udreg_entry;
 
     return OPAL_SUCCESS;
@@ -318,16 +318,15 @@ static int mca_rcache_udreg_deregister(mca_rcache_base_module_t *rcache,
                                       mca_rcache_base_registration_t *reg)
 {
     mca_rcache_udreg_module_t *rcache_udreg = (mca_rcache_udreg_module_t *) rcache;
+    int32_t ref_count = OPAL_THREAD_ADD32 (&reg->ref_count, -1);
 
-    assert(reg->ref_count > 0);
-
-    --reg->ref_count;
+    assert(ref_count >= 0);
 
     if (!(reg->flags & MCA_RCACHE_FLAGS_CACHE_BYPASS)) {
         OPAL_THREAD_LOCK(&rcache_udreg->lock);
         UDREG_DecrRefcount (rcache_udreg->udreg_handle, reg->rcache_context);
         OPAL_THREAD_UNLOCK(&rcache_udreg->lock);
-    } else if (!reg->ref_count) {
+    } else if (!ref_count) {
         mca_rcache_udreg_dereg_func (reg, rcache);
     }