IB/ipath: Add barrier before updating WC head in shared memory
Add a barrier to make sure the CPU doesn't reorder writes to memory,
since user programs can be polling on the head index update and the
entry should be written before that.
Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/ipath/ipath_ud.c b/drivers/infiniband/hw/ipath/ipath_ud.c
index 38ba771..f9a3338 100644
--- a/drivers/infiniband/hw/ipath/ipath_ud.c
+++ b/drivers/infiniband/hw/ipath/ipath_ud.c
@@ -176,6 +176,8 @@
dev->n_pkt_drops++;
goto bail_sge;
}
+ /* Make sure entry is read after head index is read. */
+ smp_rmb();
wqe = get_rwqe_ptr(rq, tail);
if (++tail >= rq->size)
tail = 0;