diff --git a/opal/mca/btl/vader/btl_vader_component.c b/opal/mca/btl/vader/btl_vader_component.c
index 586ec0da21..9e2b884a6f 100644
--- a/opal/mca/btl/vader/btl_vader_component.c
+++ b/opal/mca/btl/vader/btl_vader_component.c
@@ -633,22 +633,21 @@ static void mca_btl_vader_progress_waiting (mca_btl_base_endpoint_t *ep)
         return;
     }
 
-    OPAL_THREAD_LOCK(&ep->lock);
+    OPAL_THREAD_LOCK(&ep->pending_frags_lock);
     OPAL_LIST_FOREACH_SAFE(frag, next, &ep->pending_frags, mca_btl_vader_frag_t) {
-        OPAL_THREAD_UNLOCK(&ep->lock);
         ret = vader_fifo_write_ep (frag->hdr, ep);
         if (!ret) {
+            OPAL_THREAD_UNLOCK(&ep->pending_frags_lock);
             return;
         }
 
-        OPAL_THREAD_LOCK(&ep->lock);
         (void) opal_list_remove_first (&ep->pending_frags);
     }
 
     ep->waiting = false;
     opal_list_remove_item (&mca_btl_vader_component.pending_endpoints, &ep->super);
 
-    OPAL_THREAD_UNLOCK(&ep->lock);
+    OPAL_THREAD_UNLOCK(&ep->pending_frags_lock);
 }
 
 /**
diff --git a/opal/mca/btl/vader/btl_vader_endpoint.h b/opal/mca/btl/vader/btl_vader_endpoint.h
index bc57d2d95a..2fd957dfbb 100644
--- a/opal/mca/btl/vader/btl_vader_endpoint.h
+++ b/opal/mca/btl/vader/btl_vader_endpoint.h
@@ -62,7 +62,7 @@ typedef struct mca_btl_base_endpoint_t {
 
     int32_t peer_smp_rank;  /**< my peer's SMP process rank.  Used for accessing
                              *   SMP specfic data structures. */
-    uint32_t send_count;    /**< number of fragments sent to this peer */
+    volatile uint64_t send_count;    /**< number of fragments sent to this peer */
     char *segment_base;     /**< start of the peer's segment (in the address space
                              *   of this process) */
 
@@ -84,6 +84,7 @@ typedef struct mca_btl_base_endpoint_t {
         } other;
     } segment_data;
 
+    opal_mutex_t pending_frags_lock; /**< protect pending_frags */
     opal_list_t pending_frags; /**< fragments pending fast box space */
     bool waiting;           /**< endpoint is on the component wait list */
 } mca_btl_base_endpoint_t;
@@ -94,15 +95,15 @@ OBJ_CLASS_DECLARATION(mca_btl_vader_endpoint_t);
 
 static inline void mca_btl_vader_endpoint_setup_fbox_recv (struct mca_btl_base_endpoint_t *endpoint, void *base)
 {
-    endpoint->fbox_in.buffer = base;
     endpoint->fbox_in.startp = (uint32_t *) base;
     endpoint->fbox_in.start = MCA_BTL_VADER_FBOX_ALIGNMENT;
     endpoint->fbox_in.seq = 0;
+    opal_atomic_wmb ();
+    endpoint->fbox_in.buffer = base;
 }
 
 static inline void mca_btl_vader_endpoint_setup_fbox_send (struct mca_btl_base_endpoint_t *endpoint, void *base)
 {
-    endpoint->fbox_out.buffer = base;
     endpoint->fbox_out.start = MCA_BTL_VADER_FBOX_ALIGNMENT;
     endpoint->fbox_out.end = MCA_BTL_VADER_FBOX_ALIGNMENT;
     endpoint->fbox_out.startp = (uint32_t *) base;
@@ -111,6 +112,9 @@ static inline void mca_btl_vader_endpoint_setup_fbox_send (struct mca_btl_base_e
 
     /* zero out the first header in the fast box */
     memset ((char *) base + MCA_BTL_VADER_FBOX_ALIGNMENT, 0, MCA_BTL_VADER_FBOX_ALIGNMENT);
+
+    opal_atomic_wmb ();
+    endpoint->fbox_out.buffer = base;
 }
 
 #endif /* MCA_BTL_VADER_ENDPOINT_H */
diff --git a/opal/mca/btl/vader/btl_vader_fbox.h b/opal/mca/btl/vader/btl_vader_fbox.h
index d646263054..dfef75bb38 100644
--- a/opal/mca/btl/vader/btl_vader_fbox.h
+++ b/opal/mca/btl/vader/btl_vader_fbox.h
@@ -117,6 +117,7 @@ static inline unsigned char *mca_btl_vader_reserve_fbox (mca_btl_base_endpoint_t
 
         if (OPAL_UNLIKELY(buffer_free < size)) {
             ep->fbox_out.end = (hbs << 31) | end;
+            opal_atomic_wmb ();
             OPAL_THREAD_UNLOCK(&ep->lock);
             return NULL;
         }
@@ -141,6 +142,7 @@ static inline unsigned char *mca_btl_vader_reserve_fbox (mca_btl_base_endpoint_t
 
     /* align the buffer */
     ep->fbox_out.end = ((uint32_t) hbs << 31) | end;
+    opal_atomic_wmb ();
     OPAL_THREAD_UNLOCK(&ep->lock);
 
     return dst + sizeof (mca_btl_vader_fbox_hdr_t);
@@ -247,6 +249,7 @@ static inline bool mca_btl_vader_check_fboxes (void)
 
             /* save where we left off */
             /* let the sender know where we stopped */
+            opal_atomic_mb ();
             ep->fbox_in.start = ep->fbox_in.startp[0] = ((uint32_t) hbs << 31) | start;
             processed = true;
         }
@@ -258,8 +261,7 @@ static inline bool mca_btl_vader_check_fboxes (void)
 
 static inline void mca_btl_vader_try_fbox_setup (mca_btl_base_endpoint_t *ep, mca_btl_vader_hdr_t *hdr)
 {
-    if (NULL == ep->fbox_out.buffer && mca_btl_vader_component.fbox_threshold == ++ep->send_count) {
-
+    if (OPAL_UNLIKELY(NULL == ep->fbox_out.buffer && mca_btl_vader_component.fbox_threshold == OPAL_THREAD_ADD64 ((volatile int64_t *) &ep->send_count, 1))) {
         /* protect access to mca_btl_vader_component.segment_offset */
         OPAL_THREAD_LOCK(&mca_btl_vader_component.lock);
 
diff --git a/opal/mca/btl/vader/btl_vader_module.c b/opal/mca/btl/vader/btl_vader_module.c
index 094eb505f1..1464d007b4 100644
--- a/opal/mca/btl/vader/btl_vader_module.c
+++ b/opal/mca/btl/vader/btl_vader_module.c
@@ -524,12 +524,14 @@ static struct mca_btl_base_descriptor_t *vader_prepare_src (struct mca_btl_base_
 static void mca_btl_vader_endpoint_constructor (mca_btl_vader_endpoint_t *ep)
 {
     OBJ_CONSTRUCT(&ep->pending_frags, opal_list_t);
+    OBJ_CONSTRUCT(&ep->pending_frags_lock, opal_mutex_t);
     ep->fifo = NULL;
 }
 
 static void mca_btl_vader_endpoint_destructor (mca_btl_vader_endpoint_t *ep)
 {
     OBJ_DESTRUCT(&ep->pending_frags);
+    OBJ_DESTRUCT(&ep->pending_frags_lock);
 
 #if OPAL_BTL_VADER_HAVE_XPMEM
     if (MCA_BTL_VADER_XPMEM == mca_btl_vader_component.single_copy_mechanism) {
diff --git a/opal/mca/btl/vader/btl_vader_send.c b/opal/mca/btl/vader/btl_vader_send.c
index 59a10c366a..08bfa5a623 100644
--- a/opal/mca/btl/vader/btl_vader_send.c
+++ b/opal/mca/btl/vader/btl_vader_send.c
@@ -57,7 +57,7 @@ int mca_btl_vader_send (struct mca_btl_base_module_t *btl,
     /* post the relative address of the descriptor into the peer's fifo */
     if (opal_list_get_size (&endpoint->pending_frags) || !vader_fifo_write_ep (frag->hdr, endpoint)) {
         frag->base.des_flags |= MCA_BTL_DES_SEND_ALWAYS_CALLBACK;
-        OPAL_THREAD_LOCK(&endpoint->lock);
+        OPAL_THREAD_LOCK(&endpoint->pending_frags_lock);
         opal_list_append (&endpoint->pending_frags, (opal_list_item_t *) frag);
         if (!endpoint->waiting) {
             OPAL_THREAD_LOCK(&mca_btl_vader_component.lock);
@@ -65,7 +65,7 @@ int mca_btl_vader_send (struct mca_btl_base_module_t *btl,
             OPAL_THREAD_UNLOCK(&mca_btl_vader_component.lock);
             endpoint->waiting = true;
         }
-        OPAL_THREAD_UNLOCK(&endpoint->lock);
+        OPAL_THREAD_UNLOCK(&endpoint->pending_frags_lock);
         return OPAL_SUCCESS;
     }