Commit 12f75e8a authored by Michael J. Ruhl's avatar Michael J. Ruhl Committed by Greg Kroah-Hartman

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: <> # 4.14.0>
Reviewed-by: default avatarMitko Haralanov <>
Reviewed-by: default avatarMike Marciniszyn <>
Signed-off-by: default avatarMichael J. Ruhl <>
Signed-off-by: default avatarSasha Levin <>
parent 8f8a5a9b
......@@ -187,7 +187,6 @@ int hfi1_user_sdma_alloc_queues(struct hfi1_ctxtdata *uctxt,
pq->ctxt = uctxt->ctxt;
pq->subctxt = fd->subctxt;
pq->n_max_reqs = hfi1_sdma_comp_ring_size;
pq->state = SDMA_PKT_Q_INACTIVE;
atomic_set(&pq->n_reqs, 0);
atomic_set(&pq->n_locked, 0);
......@@ -276,7 +275,7 @@ int hfi1_user_sdma_free_queues(struct hfi1_filedata *fd,
/* Wait until all requests have been freed. */
......@@ -312,6 +311,13 @@ static u8 dlid_to_selector(u16 dlid)
return mapping[hash];
* hfi1_user_sdma_process_request() - Process and start a user sdma request
* @fd: valid file descriptor
* @iovec: array of io vectors to process
* @dim: overall iovec array size
* @count: number of io vector array entries processed
int hfi1_user_sdma_process_request(struct hfi1_filedata *fd,
struct iovec *iovec, unsigned long dim,
unsigned long *count)
......@@ -560,20 +566,12 @@ int hfi1_user_sdma_process_request(struct hfi1_filedata *fd,
req->ahg_idx = sdma_ahg_alloc(req->sde);
set_comp_state(pq, cq, info.comp_idx, QUEUED, 0);
pq->state = SDMA_PKT_Q_ACTIVE;
/* Send the first N packets in the request to buy us some time */
ret = user_sdma_send_pkts(req, pcount);
if (unlikely(ret < 0 && ret != -EBUSY))
goto free_req;
* It is possible that the SDMA engine would have processed all the
* submitted packets by the time we get here. Therefore, only set
* packet queue state to ACTIVE if there are still uncompleted
* requests.
if (atomic_read(&pq->n_reqs))
xchg(&pq->state, SDMA_PKT_Q_ACTIVE);
* This is a somewhat blocking send implementation.
* The driver will block the caller until all packets of the
......@@ -1391,10 +1389,8 @@ static void user_sdma_txreq_cb(struct sdma_txreq *txreq, int status)
static inline void pq_update(struct hfi1_user_sdma_pkt_q *pq)
if (atomic_dec_and_test(&pq->n_reqs)) {
xchg(&pq->state, SDMA_PKT_Q_INACTIVE);
if (atomic_dec_and_test(&pq->n_reqs))
static void user_sdma_free_request(struct user_sdma_request *req, bool unpin)
......@@ -94,9 +94,10 @@
#define TXREQ_FLAGS_REQ_ACK BIT(0) /* Set the ACK bit in the header */
#define TXREQ_FLAGS_REQ_DISABLE_SH BIT(1) /* Disable header suppression */
enum pkt_q_sdma_state {
* Maximum retry attempts to submit a TX request
......@@ -124,7 +125,7 @@ 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;
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