Hi I was evaluating whether it is feasible to use QAT with dm-crypt (the answer is that it is not - QAT is slower than AES-NI for this type of workload; QAT starts to be benefical for encryption requests longer than 64k). And I got some deadlocks. The reason for the deadlocks is this: suppose that one of the "if" conditions in "qat_alg_send_message_maybacklog" is true and we jump to the "enqueue" label. At this point, an interrupt comes in and clears all pending messages. Now, the interrupt returns, we grab backlog->lock, add the message to the backlog, drop backlog->lock - and there is no one to remove the backlogged message out of the list and submit it. I fixed it with this patch - with this patch, the test passes and there are no longer any deadlocks. I didn't want to add a spinlock to the hot path, so I take it only if some of the condition suggests that queuing may be required. Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/crypto/intel/qat/qat_common/qat_algs_send.c | 31 ++++++++++++-------- 1 file changed, 20 insertions(+), 11 deletions(-) Index: linux-2.6/drivers/crypto/intel/qat/qat_common/qat_algs_send.c =================================================================== --- linux-2.6.orig/drivers/crypto/intel/qat/qat_common/qat_algs_send.c +++ linux-2.6/drivers/crypto/intel/qat/qat_common/qat_algs_send.c @@ -40,16 +40,6 @@ void qat_alg_send_backlog(struct qat_ins spin_unlock_bh(&backlog->lock); } -static void qat_alg_backlog_req(struct qat_alg_req *req, - struct qat_instance_backlog *backlog) -{ - INIT_LIST_HEAD(&req->list); - - spin_lock_bh(&backlog->lock); - list_add_tail(&req->list, &backlog->list); - spin_unlock_bh(&backlog->lock); -} - static int qat_alg_send_message_maybacklog(struct qat_alg_req *req) { struct qat_instance_backlog *backlog = req->backlog; @@ -71,8 +61,27 @@ static int qat_alg_send_message_maybackl return -EINPROGRESS; enqueue: - qat_alg_backlog_req(req, backlog); + spin_lock_bh(&backlog->lock); + + /* If any request is already backlogged, then add to backlog list */ + if (!list_empty(&backlog->list)) + goto enqueue2; + /* If ring is nearly full, then add to backlog list */ + if (adf_ring_nearly_full(tx_ring)) + goto enqueue2; + + /* If adding request to HW ring fails, then add to backlog list */ + if (adf_send_message(tx_ring, fw_req)) + goto enqueue2; + + spin_unlock_bh(&backlog->lock); + return -EINPROGRESS; + +enqueue2: + list_add_tail(&req->list, &backlog->list); + + spin_unlock_bh(&backlog->lock); return -EBUSY; }