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Subject[PATCH 4.19 03/67] IB/hfi1: Remove race conditions in user_sdma send path
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

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> # 4.19.x
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: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/hw/hfi1/user_sdma.c | 24 ++++++++++--------------
drivers/infiniband/hw/hfi1/user_sdma.h | 9 +++++----
2 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/user_sdma.c b/drivers/infiniband/hw/hfi1/user_sdma.c
index 39134dd305f5..51831bfbf90f 100644
--- a/drivers/infiniband/hw/hfi1/user_sdma.c
+++ b/drivers/infiniband/hw/hfi1/user_sdma.c
@@ -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);
init_waitqueue_head(&pq->wait);
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. */
wait_event_interruptible(
pq->wait,
- (READ_ONCE(pq->state) == SDMA_PKT_Q_INACTIVE));
+ !atomic_read(&pq->n_reqs));
kfree(pq->reqs);
kfree(pq->req_in_use);
kmem_cache_destroy(pq->txreq_cache);
@@ -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
@@ -1409,10 +1407,8 @@ 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))
wake_up(&pq->wait);
- }
}

static void user_sdma_free_request(struct user_sdma_request *req, bool unpin)
diff --git a/drivers/infiniband/hw/hfi1/user_sdma.h b/drivers/infiniband/hw/hfi1/user_sdma.h
index 0ae06456c868..91c343f91776 100644
--- a/drivers/infiniband/hw/hfi1/user_sdma.h
+++ b/drivers/infiniband/hw/hfi1/user_sdma.h
@@ -105,9 +105,10 @@ static inline int ahg_header_set(u32 *arr, int idx, size_t array_size,
#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 */

-#define SDMA_PKT_Q_INACTIVE BIT(0)
-#define SDMA_PKT_Q_ACTIVE BIT(1)
-#define SDMA_PKT_Q_DEFERRED BIT(2)
+enum pkt_q_sdma_state {
+ SDMA_PKT_Q_ACTIVE,
+ SDMA_PKT_Q_DEFERRED,
+};

/*
* Maximum retry attempts to submit a TX request
@@ -133,7 +134,7 @@ 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;
--
2.19.1


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