[PATCH v2 02/20] IB/hfi1: Race hazard avoidance in user SDMA driver

[Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

From: Michael J. Ruhl <michael.j.ruhl-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Set the errcode before the state and add the smb_wmb() to avoid a
potential race condition with the user.

Reviewed-by: Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Michael Ruhl <michael.j.ruhl-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 drivers/infiniband/hw/hfi1/user_sdma.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/user_sdma.c b/drivers/infiniband/hw/hfi1/user_sdma.c
index e6811c4..060e374 100644
--- a/drivers/infiniband/hw/hfi1/user_sdma.c
+++ b/drivers/infiniband/hw/hfi1/user_sdma.c
@@ -1615,9 +1615,10 @@ static inline void set_comp_state(struct hfi1_user_sdma_pkt_q *pq,
 {
 	hfi1_cdbg(SDMA, "[%u:%u:%u:%u] Setting completion status %u %d",
 		  pq->dd->unit, pq->ctxt, pq->subctxt, idx, state, ret);
-	cq->comps[idx].status = state;
 	if (state == ERROR)
 		cq->comps[idx].errcode = -ret;
+	smp_wmb(); /* make sure errcode is visible first */
+	cq->comps[idx].status = state;
 	trace_hfi1_sdma_user_completion(pq->dd, pq->ctxt, pq->subctxt,
 					idx, state, ret);
 }

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