From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Puiu Subject: [PATCH v3] vmxnet3: fix Rx deadlock Date: Fri, 16 Dec 2016 17:36:57 +0200 Message-ID: <1481902617-16050-1-git-send-email-stefan.puiu@gmail.com> References: <1481530874-8660-1-git-send-email-stefan.puiu@gmail.com> Cc: yongwang@vmware.com, mac_leehk@yahoo.com.hk, Stefan Puiu To: dev@dpdk.org Return-path: Received: from mail-wj0-f194.google.com (mail-wj0-f194.google.com [209.85.210.194]) by dpdk.org (Postfix) with ESMTP id 34020558C for ; Fri, 16 Dec 2016 16:37:59 +0100 (CET) Received: by mail-wj0-f194.google.com with SMTP id xy5so15092153wjc.1 for ; Fri, 16 Dec 2016 07:37:59 -0800 (PST) In-Reply-To: <1481530874-8660-1-git-send-email-stefan.puiu@gmail.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Our use case is that we have an app that needs to keep mbufs around for a while. We've seen cases when calling vmxnet3_post_rx_bufs() from vmxet3_recv_pkts(), it might not succeed to add any mbufs to any RX descriptors (where it returns -err). Since there are no mbufs that the virtual hardware can use, no packets will be received after this; the driver won't refill the mbuf after this so it gets stuck in this state. I call this a deadlock for lack of a better term - the virtual HW waits for free mbufs, while the app waits for the hardware to notify it for data (by flipping the generation bit on the used Rx descriptors). Note that after this, the app can't recover. This fix is a rework of this patch by Marco Lee: http://dpdk.org/dev/patchwork/patch/6575/. I had to forward port it, address review comments and also reverted the allocation failure handling to the first version of the patch (http://dpdk.org/ml/archives/dev/2015-July/022079.html), since that's the only approach that seems to work, and seems to be what other drivers are doing (I checked ixgbe and em). Reusing the mbuf that's getting passed to the application doesn't seem to make sense, and it was causing weird issues in our app. Also, reusing rxm without checking if it's NULL could cause the code to crash. --- v3: * rework description after review, explain how HW signal receipt of packets v2: * address review comments, reworded description a bit drivers/net/vmxnet3/vmxnet3_rxtx.c | 39 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 37 insertions(+), 2 deletions(-) diff --git a/drivers/net/vmxnet3/vmxnet3_rxtx.c b/drivers/net/vmxnet3/vmxnet3_rxtx.c index b109168..93db10f 100644 --- a/drivers/net/vmxnet3/vmxnet3_rxtx.c +++ b/drivers/net/vmxnet3/vmxnet3_rxtx.c @@ -518,6 +518,32 @@ return nb_tx; } +static inline void +vmxnet3_renew_desc(vmxnet3_rx_queue_t *rxq, uint8_t ring_id, + struct rte_mbuf *mbuf) +{ + uint32_t val = 0; + struct vmxnet3_cmd_ring *ring = &rxq->cmd_ring[ring_id]; + struct Vmxnet3_RxDesc *rxd = + (struct Vmxnet3_RxDesc *)(ring->base + ring->next2fill); + vmxnet3_buf_info_t *buf_info = &ring->buf_info[ring->next2fill]; + + if (ring_id == 0) + val = VMXNET3_RXD_BTYPE_HEAD; + else + val = VMXNET3_RXD_BTYPE_BODY; + + buf_info->m = mbuf; + buf_info->len = (uint16_t)(mbuf->buf_len - RTE_PKTMBUF_HEADROOM); + buf_info->bufPA = rte_mbuf_data_dma_addr_default(mbuf); + + rxd->addr = buf_info->bufPA; + rxd->btype = val; + rxd->len = buf_info->len; + rxd->gen = ring->gen; + + vmxnet3_cmd_ring_adv_next2fill(ring); +} /* * Allocates mbufs and clusters. Post rx descriptors with buffer details * so that device can receive packets in those buffers. @@ -657,9 +683,18 @@ } while (rcd->gen == rxq->comp_ring.gen) { + struct rte_mbuf *newm; + if (nb_rx >= nb_pkts) break; + newm = rte_mbuf_raw_alloc(rxq->mp); + if (unlikely(newm == NULL)) { + PMD_RX_LOG(ERR, "Error allocating mbuf"); + rxq->stats.rx_buf_alloc_failure++; + break; + } + idx = rcd->rxdIdx; ring_idx = (uint8_t)((rcd->rqID == rxq->qid1) ? 0 : 1); rxd = (Vmxnet3_RxDesc *)rxq->cmd_ring[ring_idx].base + idx; @@ -759,8 +794,8 @@ VMXNET3_INC_RING_IDX_ONLY(rxq->cmd_ring[ring_idx].next2comp, rxq->cmd_ring[ring_idx].size); - /* It's time to allocate some new buf and renew descriptors */ - vmxnet3_post_rx_bufs(rxq, ring_idx); + /* It's time to renew descriptors */ + vmxnet3_renew_desc(rxq, ring_idx, newm); if (unlikely(rxq->shared->ctrl.updateRxProd)) { VMXNET3_WRITE_BAR0_REG(hw, rxprod_reg[ring_idx] + (rxq->queue_id * VMXNET3_REG_ALIGN), rxq->cmd_ring[ring_idx].next2fill); -- 1.9.1