From 74cff0e2a51111fcea3a945246b3fed5083d501c Mon Sep 17 00:00:00 2001
From: Samuel Gutierrez <samuel@lanl.gov>
Date: Mon, 29 Nov 2010 15:57:54 +0000
Subject: [PATCH] Update memory barriers in shared memory (sm) BTL.  Fixes
 periodic segmentation faults when using Intel 10.0.025 or PGI 9.0-3.  See
 #2619 for more details.  Thanks Brian and George!

This commit was SVN r24095.
---
 ompi/mca/btl/sm/btl_sm.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ompi/mca/btl/sm/btl_sm.h b/ompi/mca/btl/sm/btl_sm.h
index 1058b8a7f6..fabdbd4348 100644
--- a/ompi/mca/btl/sm/btl_sm.h
+++ b/ompi/mca/btl/sm/btl_sm.h
@@ -334,12 +334,13 @@ static inline int sm_fifo_write(void *value, sm_fifo_t *fifo)
     volatile void **q = (volatile void **) RELATIVE2VIRTUAL(fifo->queue);
 
     /* if there is no free slot to write, report exhausted resource */
+    opal_atomic_rmb();
     if ( SM_FIFO_FREE != q[fifo->head] )
         return OMPI_ERR_OUT_OF_RESOURCE;
 
     /* otherwise, write to the slot and advance the head index */
-    opal_atomic_rmb();
     q[fifo->head] = value;
+    opal_atomic_wmb();
     fifo->head = (fifo->head + 1) & fifo->mask;
     opal_atomic_wmb(); 
     return OMPI_SUCCESS;