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[2603:8081:140c:1a00:5c63:4cee:84ac:42bc]) by smtp.googlemail.com with ESMTPSA id t21sm8304929otq.81.2022.01.31.14.10.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Jan 2022 14:10:11 -0800 (PST) From: Bob Pearson To: jgg@nvidia.com, zyjzyj2000@gmail.com, linux-rdma@vger.kernel.org Cc: Bob Pearson Subject: [PATCH for-next v10 10/17] RDMA/rxe: Split rxe_rcv_mcast_pkt into two phases Date: Mon, 31 Jan 2022 16:08:43 -0600 Message-Id: <20220131220849.10170-11-rpearsonhpe@gmail.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220131220849.10170-1-rpearsonhpe@gmail.com> References: <20220131220849.10170-1-rpearsonhpe@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org Currently rxe_rcv_mcast_pkt performs most of its work under the mcg->mcg_lock and calls into rxe_rcv which queues the packets to the responder and completer tasklets holding the lock which is a very bad idea. This patch walks the qp_list in mcg and copies the qp addresses to a dynamically allocated array under the lock but does the rest of the work without holding the lock. The critical section is now very small. Signed-off-by: Bob Pearson --- drivers/infiniband/sw/rxe/rxe_mcast.c | 11 ++++--- drivers/infiniband/sw/rxe/rxe_recv.c | 41 +++++++++++++++++++++------ drivers/infiniband/sw/rxe/rxe_verbs.h | 2 +- 3 files changed, 38 insertions(+), 16 deletions(-) diff --git a/drivers/infiniband/sw/rxe/rxe_mcast.c b/drivers/infiniband/sw/rxe/rxe_mcast.c index 29e6c9e11c77..52bd46ca22c9 100644 --- a/drivers/infiniband/sw/rxe/rxe_mcast.c +++ b/drivers/infiniband/sw/rxe/rxe_mcast.c @@ -122,16 +122,16 @@ static int rxe_mcast_add_grp_elem(struct rxe_dev *rxe, struct rxe_qp *qp, } mca = new_mca; - if (mcg->num_qp >= rxe->attr.max_mcast_qp_attach) { + if (atomic_read(&mcg->qp_num) >= rxe->attr.max_mcast_qp_attach) { err = -ENOMEM; goto out; } - mcg->num_qp++; + atomic_inc(&mcg->qp_num); mca->qp = qp; atomic_inc(&qp->mcg_num); - list_add(&mca->qp_list, &mcg->qp_list); + list_add_tail(&mca->qp_list, &mcg->qp_list); err = 0; out: @@ -154,8 +154,7 @@ static int rxe_mcast_drop_grp_elem(struct rxe_dev *rxe, struct rxe_qp *qp, list_for_each_entry_safe(mca, tmp, &mcg->qp_list, qp_list) { if (mca->qp == qp) { list_del(&mca->qp_list); - mcg->num_qp--; - if (mcg->num_qp <= 0) + if (atomic_dec_return(&mcg->qp_num) <= 0) __rxe_destroy_mcg(mcg); atomic_dec(&qp->mcg_num); @@ -190,7 +189,7 @@ int rxe_attach_mcast(struct ib_qp *ibqp, union ib_gid *mgid, u16 mlid) err = rxe_mcast_add_grp_elem(rxe, qp, mcg); - if (mcg->num_qp == 0) + if (atomic_read(&mcg->qp_num) == 0) __rxe_destroy_mcg(mcg); rxe_drop_ref(mcg); diff --git a/drivers/infiniband/sw/rxe/rxe_recv.c b/drivers/infiniband/sw/rxe/rxe_recv.c index 10020103ea4a..ed80125f1dc5 100644 --- a/drivers/infiniband/sw/rxe/rxe_recv.c +++ b/drivers/infiniband/sw/rxe/rxe_recv.c @@ -229,6 +229,11 @@ static inline void rxe_rcv_pkt(struct sk_buff *skb) rxe_comp_queue_pkt(RXECB(skb)->qp, skb); } +/* split processing of the qp list into two stages. + * first just make a simple linear array from the + * current list while holding the lock and then + * process each qp without holding the lock. + */ static void rxe_rcv_mcast_pkt(struct sk_buff *skb) { struct sk_buff *s; @@ -237,7 +242,9 @@ static void rxe_rcv_mcast_pkt(struct sk_buff *skb) struct rxe_mcg *mcg; struct rxe_mca *mca; struct rxe_qp *qp; + struct rxe_qp **qp_array; union ib_gid dgid; + int n, nmax; int err; if (skb->protocol == htons(ETH_P_IP)) @@ -251,15 +258,32 @@ static void rxe_rcv_mcast_pkt(struct sk_buff *skb) if (!mcg) goto drop; /* mcast group not registered */ + /* this is the current number of qp's attached to mcg plus a + * little room in case new qp's are attached. It isn't wrong + * to miss some qp's since it is just a matter of precisely + * when the packet is assumed to be received. + */ + nmax = atomic_read(&mcg->qp_num) + 2; + qp_array = kmalloc_array(nmax, sizeof(qp), GFP_KERNEL); + + n = 0; spin_lock_bh(&mcg->mcg_lock); + list_for_each_entry(mca, &mcg->qp_list, qp_list) { + rxe_add_ref(mca->qp); + qp_array[n++] = mca->qp; + if (n == nmax) + break; + } + spin_unlock_bh(&mcg->mcg_lock); + nmax = n; /* this is unreliable datagram service so we let * failures to deliver a multicast packet to a * single QP happen and just move on and try * the rest of them on the list */ - list_for_each_entry(mca, &mcg->qp_list, qp_list) { - qp = mca->qp; + for (n = 0; n < nmax; n++) { + qp = qp_array[n]; /* validate qp for incoming packet */ err = check_type_state(rxe, pkt, qp); @@ -274,28 +298,27 @@ static void rxe_rcv_mcast_pkt(struct sk_buff *skb) * skb and pass to the QP. Pass the original skb to * the last QP in the list. */ - if (mca->qp_list.next != &mcg->qp_list) { - s = skb_clone(skb, GFP_ATOMIC); + if (n < nmax - 1) { + s = skb_clone(skb, GFP_KERNEL); if (unlikely(!s)) continue; + RXECB(s)->qp = qp; if (WARN_ON(!ib_device_try_get(&rxe->ib_dev))) { + rxe_drop_ref(RXECB(s)->qp); kfree_skb(s); - break; + continue; } - RXECB(s)->qp = qp; - rxe_add_ref(qp); rxe_rcv_pkt(s); } else { RXECB(skb)->qp = qp; - rxe_add_ref(qp); rxe_rcv_pkt(skb); skb = NULL; /* mark consumed */ } } - spin_unlock_bh(&mcg->mcg_lock); + kfree(qp_array); rxe_drop_ref(mcg); /* drop ref from rxe_pool_get_key. */ diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h index 02745d51c163..d65c358798c6 100644 --- a/drivers/infiniband/sw/rxe/rxe_verbs.h +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h @@ -356,8 +356,8 @@ struct rxe_mcg { spinlock_t mcg_lock; /* guard group */ struct rxe_dev *rxe; struct list_head qp_list; + atomic_t qp_num; union ib_gid mgid; - int num_qp; u32 qkey; u16 pkey; };