Messages in this thread Patch in this message |  | | Subject | Re: [PATCH v5 3/3] RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs #2 | From | Sinan Kaya <> | Date | Mon, 2 Apr 2018 22:29:53 -0400 |
| |
On 3/22/2018 12:26 PM, Sinan Kaya wrote: > @@ -860,7 +860,7 @@ static void doorbell_cq(struct qedr_cq *cq, u32 cons, u8 flags) > wmb(); > cq->db.data.agg_flags = flags; > cq->db.data.value = cpu_to_le32(cons); > - writeq(cq->db.raw, cq->db_addr); > + writeq_relaxed(cq->db.raw, cq->db_addr);
Given the direction to get rid of wmb() in front of writeX() functions, I have been reviewing this code. Under normal circumstances, I can get rid of all wmb() as follows.
However, I started having my doubts now. Are these wmb() used as a SMP barrier too? I can't find any smp_Xmb() in drivers/infiniband/hw/qedr directory.
static void doorbell_cq(struct qedr_cq *cq, u32 cons, u8 flags) { - /* Flush data before signalling doorbell */ - wmb(); cq->db.data.agg_flags = flags; cq->db.data.value = cpu_to_le32(cons); writeq(cq->db.raw, cq->db_addr); @@ -1870,8 +1868,7 @@ static int qedr_update_qp_state(struct qedr_dev *dev, */
if (rdma_protocol_roce(&dev->ibdev, 1)) { - wmb(); - writel_relaxed(qp->rq.db_data.raw, qp->rq.db); + writel(qp->rq.db_data.raw, qp->rq.db); /* Make sure write takes effect */ mmiowb(); } @@ -3275,8 +3272,7 @@ int qedr_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr, * unchanged). For performance reasons we avoid checking for this * redundant doorbell. */ - wmb(); - writel_relaxed(qp->sq.db_data.raw, qp->sq.db); + writel(qp->sq.db_data.raw, qp->sq.db);
/* Make sure write sticks */ mmiowb(); @@ -3362,9 +3358,6 @@ int qedr_post_recv(struct ib_qp *ibqp, struct ib_recv_wr *wr,
qedr_inc_sw_prod(&qp->rq);
- /* Flush all the writes before signalling doorbell */ - wmb();
-- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
|  |