IB/hfi1: Remove race conditions in user_sdma send path

commit 28a9a9e83ceae2cee25b9af9ad20d53aaa9ab951 upstream

Packet queue state is over used to determine SDMA descriptor
availablitity and packet queue request state.

cpu 0  ret = user_sdma_send_pkts(req, pcount);
cpu 0  if (atomic_read(&pq->n_reqs))
cpu 1  IRQ user_sdma_txreq_cb calls pq_update() (state to _INACTIVE)
cpu 0        xchg(&pq->state, SDMA_PKT_Q_ACTIVE);

At this point pq->n_reqs == 0 and pq->state is incorrectly
SDMA_PKT_Q_ACTIVE.  The close path will hang waiting for the state
to return to _INACTIVE.

This can also change the state from _DEFERRED to _ACTIVE.  However,
this is a mostly benign race.

Remove the racy code path.

Use n_reqs to determine if a packet queue is active or not.

Cc: <stable@vger.kernel.org> # 4.9.0
Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/hfi1/user_sdma.h b/drivers/infiniband/hw/hfi1/user_sdma.h
index 39001714f551..09dd843a13de 100644
--- a/drivers/infiniband/hw/hfi1/user_sdma.h
+++ b/drivers/infiniband/hw/hfi1/user_sdma.h
@@ -53,6 +53,11 @@
 
 extern uint extended_psn;
 
+enum pkt_q_sdma_state {
+	SDMA_PKT_Q_ACTIVE,
+	SDMA_PKT_Q_DEFERRED,
+};
+
 struct hfi1_user_sdma_pkt_q {
 	struct list_head list;
 	unsigned ctxt;
@@ -65,7 +70,7 @@ struct hfi1_user_sdma_pkt_q {
 	struct user_sdma_request *reqs;
 	unsigned long *req_in_use;
 	struct iowait busy;
-	unsigned state;
+	enum pkt_q_sdma_state state;
 	wait_queue_head_t wait;
 	unsigned long unpinned;
 	struct mmu_rb_handler *handler;