From patchwork Mon Nov 11 23:39:59 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ousterhout X-Patchwork-Id: 13871458 X-Patchwork-Delegate: kuba@kernel.org Received: from smtp1.cs.Stanford.EDU (smtp1.cs.stanford.edu [171.64.64.25]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 61BDF1BDAAF for ; Mon, 11 Nov 2024 23:40:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=171.64.64.25 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731368452; cv=none; b=ab8mlK1xHTjRYu50/Vsb9xRNEzJQ5kDKx08PK3La1ihRsbxXCKOG8gS3OihCWCs5GeGFr331nCRhl5oY91yBZEyrqRtM7lP0dBXfyTSbQvy8EzRRF7TEv+S2wGRVDSVtjCvCnIM2PKamc+6ImqbSWH9IPXs3WU5dSxrVlF2pAK8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731368452; c=relaxed/simple; bh=4suU7x6oP7OFTncfPKkv+UBYzyrpQT7Pbe5FEoSOxjE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=C4wHwF4vngKrYfUYLkMiNvoXLM4NWxEExfhPiz6SnAqgd0D+vi4FzvSO79axyIYhL3yYYYWQ6xbKPr/EumLAWW1luHd1cGGAjeeNw5Q9IQewjRLs7EZf1nNcQeEkLSGyuR/mlXZ5u09KWVcy0Wf5qHJEs/80KZ4Zw6iyPtxSEns= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=cs.stanford.edu; spf=pass smtp.mailfrom=cs.stanford.edu; dkim=pass (2048-bit key) header.d=cs.stanford.edu header.i=@cs.stanford.edu header.b=K9827/HT; arc=none smtp.client-ip=171.64.64.25 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=cs.stanford.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cs.stanford.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cs.stanford.edu header.i=@cs.stanford.edu header.b="K9827/HT" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=cs.stanford.edu; s=cs2308; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=C2Aw7yKXG7wvNec5VTC80ONdrzreFnGvOD9mSAlDjT0=; t=1731368450; x=1732232450; b=K9827/HTcufR6K27HYFRnas0bcSPdMXLp7mbbwRkCnnq0tFrHs1WyTpGF61IcN5S/63vosjA+Ns VExPEjVjFi65zpkjEhR5+ZtzkoTinLm8dRSdqABxMmnWAVQg26RP9NiBYf/kNvGRpc31rNfLwAWE1 420SbMGIvyAvypsbRYwiWtQ2W3+MtM79e3mdhjsMfD36Rkb2oKUIUINi3rUWVltgIyfUvqjviDEpu oTzaHa7R8Gexi1PLiEiisMIqcnfqMrUnY++fwxkVDDNBeyno1bqhKYmN+PJr+1BNCWilxe5adkK3Q OluhcW/3Dx3BCNc6AQo01ddNDxUrfJtHxEjg==; Received: from ouster448.stanford.edu ([172.24.72.71]:54467 helo=localhost.localdomain) by smtp1.cs.Stanford.EDU with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1tAe1Y-0002NP-IV; Mon, 11 Nov 2024 15:40:50 -0800 From: John Ousterhout To: netdev@vger.kernel.org, linux-api@vger.kernel.org Cc: John Ousterhout Subject: [PATCH net-next v2 06/12] net: homa: create homa_peer.h and homa_peer.c Date: Mon, 11 Nov 2024 15:39:59 -0800 Message-ID: <20241111234006.5942-7-ouster@cs.stanford.edu> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20241111234006.5942-1-ouster@cs.stanford.edu> References: <20241111234006.5942-1-ouster@cs.stanford.edu> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Score: -101.0 X-Scan-Signature: f5202e84dfa637b272337b0c5c517531 X-Patchwork-Delegate: kuba@kernel.org Homa needs to keep a small amount of information for each peer that it has communicated with. These files define that state and provide functions for storing and accessing it. Signed-off-by: John Ousterhout --- net/homa/homa_peer.c | 319 +++++++++++++++++++++++++++++++++++++++++++ net/homa/homa_peer.h | 234 +++++++++++++++++++++++++++++++ 2 files changed, 553 insertions(+) create mode 100644 net/homa/homa_peer.c create mode 100644 net/homa/homa_peer.h diff --git a/net/homa/homa_peer.c b/net/homa/homa_peer.c new file mode 100644 index 000000000000..7762064cb9e1 --- /dev/null +++ b/net/homa/homa_peer.c @@ -0,0 +1,319 @@ +// SPDX-License-Identifier: BSD-2-Clause + +/* This file provides functions related to homa_peer and homa_peertab + * objects. + */ + +#include "homa_impl.h" +#include "homa_peer.h" +#include "homa_rpc.h" + +/** + * homa_peertab_init() - Constructor for homa_peertabs. + * @peertab: The object to initialize; previous contents are discarded. + * + * Return: 0 in the normal case, or a negative errno if there was a problem. + */ +int homa_peertab_init(struct homa_peertab *peertab) +{ + /* Note: when we return, the object must be initialized so it's + * safe to call homa_peertab_destroy, even if this function returns + * an error. + */ + int i; + + spin_lock_init(&peertab->write_lock); + INIT_LIST_HEAD(&peertab->dead_dsts); + peertab->buckets = vmalloc(HOMA_PEERTAB_BUCKETS * + sizeof(*peertab->buckets)); + if (!peertab->buckets) + return -ENOMEM; + for (i = 0; i < HOMA_PEERTAB_BUCKETS; i++) + INIT_HLIST_HEAD(&peertab->buckets[i]); + return 0; +} + +/** + * homa_peertab_destroy() - Destructor for homa_peertabs. After this + * function returns, it is unsafe to use any results from previous calls + * to homa_peer_find, since all existing homa_peer objects will have been + * destroyed. + * @peertab: The table to destroy. + */ +void homa_peertab_destroy(struct homa_peertab *peertab) +{ + struct hlist_node *next; + struct homa_peer *peer; + int i; + + if (!peertab->buckets) + return; + + for (i = 0; i < HOMA_PEERTAB_BUCKETS; i++) { + hlist_for_each_entry_safe(peer, next, &peertab->buckets[i], + peertab_links) { + dst_release(peer->dst); + kfree(peer); + } + } + vfree(peertab->buckets); + homa_peertab_gc_dsts(peertab, ~0); +} + +/** + * homa_peertab_gc_dsts() - Invoked to free unused dst_entries, if it is + * safe to do so. + * @peertab: The table in which to free entries. + * @now: Current time, in sched_clock() units; entries with expiration + * dates no later than this will be freed. Specify ~0 to + * free all entries. + */ +void homa_peertab_gc_dsts(struct homa_peertab *peertab, __u64 now) +{ + while (!list_empty(&peertab->dead_dsts)) { + struct homa_dead_dst *dead = list_first_entry(&peertab->dead_dsts, + struct homa_dead_dst, + dst_links); + if (dead->gc_time > now) + break; + dst_release(dead->dst); + list_del(&dead->dst_links); + kfree(dead); + } +} + +/** + * homa_peer_find() - Returns the peer associated with a given host; creates + * a new homa_peer if one doesn't already exist. + * @peertab: Peer table in which to perform lookup. + * @addr: Address of the desired host: IPv4 addresses are represented + * as IPv4-mapped IPv6 addresses. + * @inet: Socket that will be used for sending packets. + * + * Return: The peer associated with @addr, or a negative errno if an + * error occurred. The caller can retain this pointer + * indefinitely: peer entries are never deleted except in + * homa_peertab_destroy. + */ +struct homa_peer *homa_peer_find(struct homa_peertab *peertab, + const struct in6_addr *addr, + struct inet_sock *inet) +{ + /* Note: this function uses RCU operators to ensure safety even + * if a concurrent call is adding a new entry. + */ + struct homa_peer *peer; + struct dst_entry *dst; + + // Should use siphash or jhash here: + __u32 bucket = hash_32((__force __u32)addr->in6_u.u6_addr32[0], + HOMA_PEERTAB_BUCKET_BITS); + + bucket ^= hash_32((__force __u32)addr->in6_u.u6_addr32[1], + HOMA_PEERTAB_BUCKET_BITS); + bucket ^= hash_32((__force __u32)addr->in6_u.u6_addr32[2], + HOMA_PEERTAB_BUCKET_BITS); + bucket ^= hash_32((__force __u32)addr->in6_u.u6_addr32[3], + HOMA_PEERTAB_BUCKET_BITS); + hlist_for_each_entry_rcu(peer, &peertab->buckets[bucket], + peertab_links) { + if (ipv6_addr_equal(&peer->addr, addr)) + return peer; + } + + /* No existing entry; create a new one. + * + * Note: after we acquire the lock, we have to check again to + * make sure the entry still doesn't exist (it might have been + * created by a concurrent invocation of this function). + */ + spin_lock_bh(&peertab->write_lock); + hlist_for_each_entry_rcu(peer, &peertab->buckets[bucket], + peertab_links) { + if (ipv6_addr_equal(&peer->addr, addr)) + goto done; + } + peer = kmalloc(sizeof(*peer), GFP_ATOMIC); + if (!peer) { + peer = (struct homa_peer *)ERR_PTR(-ENOMEM); + goto done; + } + peer->addr = *addr; + dst = homa_peer_get_dst(peer, inet); + if (IS_ERR(dst)) { + kfree(peer); + peer = (struct homa_peer *)PTR_ERR(dst); + goto done; + } + peer->dst = dst; + INIT_LIST_HEAD(&peer->grantable_rpcs); + INIT_LIST_HEAD(&peer->grantable_links); + hlist_add_head_rcu(&peer->peertab_links, &peertab->buckets[bucket]); + peer->outstanding_resends = 0; + peer->most_recent_resend = 0; + peer->least_recent_rpc = NULL; + peer->least_recent_ticks = 0; + peer->current_ticks = -1; + peer->resend_rpc = NULL; + peer->num_acks = 0; + spin_lock_init(&peer->ack_lock); + +done: + spin_unlock_bh(&peertab->write_lock); + return peer; +} + +/** + * homa_dst_refresh() - This method is called when the dst for a peer is + * obsolete; it releases that dst and creates a new one. + * @peertab: Table containing the peer. + * @peer: Peer whose dst is obsolete. + * @hsk: Socket that will be used to transmit data to the peer. + */ +void homa_dst_refresh(struct homa_peertab *peertab, struct homa_peer *peer, + struct homa_sock *hsk) +{ + struct dst_entry *dst; + + spin_lock_bh(&peertab->write_lock); + dst = homa_peer_get_dst(peer, &hsk->inet); + if (!IS_ERR(dst)) { + struct homa_dead_dst *dead = (struct homa_dead_dst *) + kmalloc(sizeof(*dead), GFP_KERNEL); + if (unlikely(!dead)) { + /* Can't allocate memory to keep track of the + * dead dst; just free it immediately (a bit + * risky, admittedly). + */ + dst_release(peer->dst); + } else { + __u64 now = sched_clock(); + + dead->dst = peer->dst; + dead->gc_time = now + 125000000; + list_add_tail(&dead->dst_links, &peertab->dead_dsts); + homa_peertab_gc_dsts(peertab, now); + } + peer->dst = dst; + } + spin_unlock_bh(&peertab->write_lock); +} + +/** + * homa_peer_get_dst() - Find an appropriate dst structure (either IPv4 + * or IPv6) for a peer. + * @peer: The peer for which a dst is needed. Note: this peer's flow + * struct will be overwritten. + * @inet: Socket that will be used for sending packets. + * Return: The dst structure (or an ERR_PTR). + */ +struct dst_entry *homa_peer_get_dst(struct homa_peer *peer, + struct inet_sock *inet) +{ + memset(&peer->flow, 0, sizeof(peer->flow)); + if (inet->sk.sk_family == AF_INET) { + struct rtable *rt; + + flowi4_init_output(&peer->flow.u.ip4, inet->sk.sk_bound_dev_if, + inet->sk.sk_mark, inet->tos, RT_SCOPE_UNIVERSE, + inet->sk.sk_protocol, 0, + peer->addr.in6_u.u6_addr32[3], inet->inet_saddr, + 0, 0, inet->sk.sk_uid); + security_sk_classify_flow(&inet->sk, &peer->flow.u.__fl_common); + rt = ip_route_output_flow(sock_net(&inet->sk), + &peer->flow.u.ip4, &inet->sk); + if (IS_ERR(rt)) + return (struct dst_entry *)(PTR_ERR(rt)); + return &rt->dst; + } + peer->flow.u.ip6.flowi6_oif = inet->sk.sk_bound_dev_if; + peer->flow.u.ip6.flowi6_iif = LOOPBACK_IFINDEX; + peer->flow.u.ip6.flowi6_mark = inet->sk.sk_mark; + peer->flow.u.ip6.flowi6_scope = RT_SCOPE_UNIVERSE; + peer->flow.u.ip6.flowi6_proto = inet->sk.sk_protocol; + peer->flow.u.ip6.flowi6_flags = 0; + peer->flow.u.ip6.flowi6_secid = 0; + peer->flow.u.ip6.flowi6_tun_key.tun_id = 0; + peer->flow.u.ip6.flowi6_uid = inet->sk.sk_uid; + peer->flow.u.ip6.daddr = peer->addr; + peer->flow.u.ip6.saddr = inet->pinet6->saddr; + peer->flow.u.ip6.fl6_dport = 0; + peer->flow.u.ip6.fl6_sport = 0; + peer->flow.u.ip6.mp_hash = 0; + peer->flow.u.ip6.__fl_common.flowic_tos = inet->tos; + peer->flow.u.ip6.flowlabel = ip6_make_flowinfo(inet->tos, 0); + security_sk_classify_flow(&inet->sk, &peer->flow.u.__fl_common); + return ip6_dst_lookup_flow(sock_net(&inet->sk), &inet->sk, + &peer->flow.u.ip6, NULL); +} + +/** + * homa_peer_lock_slow() - This function implements the slow path for + * acquiring a peer's @unacked_lock. It is invoked when the lock isn't + * immediately available. It waits for the lock, but also records statistics + * about the waiting time. + * @peer: Peer to lock. + */ +void homa_peer_lock_slow(struct homa_peer *peer) + __acquires(&peer->ack_lock) +{ + spin_lock_bh(&peer->ack_lock); +} + +/** + * homa_peer_add_ack() - Add a given RPC to the list of unacked + * RPCs for its server. Once this method has been invoked, it's safe + * to delete the RPC, since it will eventually be acked to the server. + * @rpc: Client RPC that has now completed. + */ +void homa_peer_add_ack(struct homa_rpc *rpc) +{ + struct homa_peer *peer = rpc->peer; + struct ack_header ack; + + homa_peer_lock(peer); + if (peer->num_acks < HOMA_MAX_ACKS_PER_PKT) { + peer->acks[peer->num_acks].client_id = cpu_to_be64(rpc->id); + peer->acks[peer->num_acks].client_port = htons(rpc->hsk->port); + peer->acks[peer->num_acks].server_port = htons(rpc->dport); + peer->num_acks++; + homa_peer_unlock(peer); + return; + } + + /* The peer has filled up; send an ACK message to empty it. The + * RPC in the message header will also be considered ACKed. + */ + memcpy(ack.acks, peer->acks, sizeof(peer->acks)); + ack.num_acks = htons(peer->num_acks); + peer->num_acks = 0; + homa_peer_unlock(peer); + homa_xmit_control(ACK, &ack, sizeof(ack), rpc); +} + +/** + * homa_peer_get_acks() - Copy acks out of a peer, and remove them from the + * peer. + * @peer: Peer to check for possible unacked RPCs. + * @count: Maximum number of acks to return. + * @dst: The acks are copied to this location. + * + * Return: The number of acks extracted from the peer (<= count). + */ +int homa_peer_get_acks(struct homa_peer *peer, int count, struct homa_ack *dst) +{ + /* Don't waste time acquiring the lock if there are no ids available. */ + if (peer->num_acks == 0) + return 0; + + homa_peer_lock(peer); + + if (count > peer->num_acks) + count = peer->num_acks; + memcpy(dst, &peer->acks[peer->num_acks - count], + count * sizeof(peer->acks[0])); + peer->num_acks -= count; + + homa_peer_unlock(peer); + return count; +} diff --git a/net/homa/homa_peer.h b/net/homa/homa_peer.h new file mode 100644 index 000000000000..2bec66e5818f --- /dev/null +++ b/net/homa/homa_peer.h @@ -0,0 +1,234 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ + +/* This file contains definitions related to managing peers (homa_peer + * and homa_peertab). + */ + +#ifndef _HOMA_PEER_H +#define _HOMA_PEER_H + +#include "homa_wire.h" +#include "homa_sock.h" + +struct homa_rpc; + +/** + * struct homa_dead_dst - Used to retain dst_entries that are no longer + * needed, until it is safe to delete them (I'm not confident that the RCU + * mechanism will be safe for these: the reference count could get incremented + * after it's on the RCU list?). + */ +struct homa_dead_dst { + /** @dst: Entry that is no longer used by a struct homa_peer. */ + struct dst_entry *dst; + + /** + * @gc_time: Time (in units of sched_clock()) when it is safe + * to free @dst. + */ + __u64 gc_time; + + /** @dst_links: Used to link together entries in peertab->dead_dsts. */ + struct list_head dst_links; +}; + +/** + * define HOMA_PEERTAB_BUCKETS - Number of bits in the bucket index for a + * homa_peertab. Should be large enough to hold an entry for every server + * in a datacenter without long hash chains. + */ +#define HOMA_PEERTAB_BUCKET_BITS 16 + +/** define HOME_PEERTAB_BUCKETS - Number of buckets in a homa_peertab. */ +#define HOMA_PEERTAB_BUCKETS BIT(HOMA_PEERTAB_BUCKET_BITS) + +/** + * struct homa_peertab - A hash table that maps from IPv6 addresses + * to homa_peer objects. IPv4 entries are encapsulated as IPv6 addresses. + * Entries are gradually added to this table, but they are never removed + * except when the entire table is deleted. We can't safely delete because + * results returned by homa_peer_find may be retained indefinitely. + * + * This table is managed exclusively by homa_peertab.c, using RCU to + * permit efficient lookups. + */ +struct homa_peertab { + /** + * @write_lock: Synchronizes addition of new entries; not needed + * for lookups (RCU is used instead). + */ + spinlock_t write_lock; + + /** + * @dead_dsts: List of dst_entries that are waiting to be deleted. + * Hold @write_lock when manipulating. + */ + struct list_head dead_dsts; + + /** + * @buckets: Pointer to heads of chains of homa_peers for each bucket. + * Malloc-ed, and must eventually be freed. NULL means this structure + * has not been initialized. + */ + struct hlist_head *buckets; +}; + +/** + * struct homa_peer - One of these objects exists for each machine that we + * have communicated with (either as client or server). + */ +struct homa_peer { + /** + * @addr: IPv6 address for the machine (IPv4 addresses are stored + * as IPv4-mapped IPv6 addresses). + */ + struct in6_addr addr; + + /** @flow: Addressing info needed to send packets. */ + struct flowi flow; + + /** + * @dst: Used to route packets to this peer; we own a reference + * to this, which we must eventually release. + */ + struct dst_entry *dst; + + /** + * grantable_rpcs: Contains all homa_rpcs (both requests and + * responses) involving this peer whose msgins require (or required + * them in the past) and have not been fully received. The list is + * sorted in priority order (head has fewest bytes_remaining). + * Locked with homa->grantable_lock. + */ + struct list_head grantable_rpcs; + + /** + * @grantable_links: Used to link this peer into homa->grantable_peers. + * If this RPC is not linked into homa->grantable_peers, this is an + * empty list pointing to itself. + */ + struct list_head grantable_links; + + /** + * @peertab_links: Links this object into a bucket of its + * homa_peertab. + */ + struct hlist_node peertab_links; + + /** + * @outstanding_resends: the number of resend requests we have + * sent to this server (spaced @homa.resend_interval apart) since + * we received a packet from this peer. + */ + int outstanding_resends; + + /** + * @most_recent_resend: @homa->timer_ticks when the most recent + * resend was sent to this peer. + */ + int most_recent_resend; + + /** + * @least_recent_rpc: of all the RPCs for this peer scanned at + * @current_ticks, this is the RPC whose @resend_timer_ticks + * is farthest in the past. + */ + struct homa_rpc *least_recent_rpc; + + /** + * @least_recent_ticks: the @resend_timer_ticks value for + * @least_recent_rpc. + */ + __u32 least_recent_ticks; + + /** + * @current_ticks: the value of @homa->timer_ticks the last time + * that @least_recent_rpc and @least_recent_ticks were computed. + * Used to detect the start of a new homa_timer pass. + */ + __u32 current_ticks; + + /** + * @resend_rpc: the value of @least_recent_rpc computed in the + * previous homa_timer pass. This RPC will be issued a RESEND + * in the current pass, if it still needs one. + */ + struct homa_rpc *resend_rpc; + + /** + * @num_acks: the number of (initial) entries in @acks that + * currently hold valid information. + */ + int num_acks; + + /** + * @acks: info about client RPCs whose results have been completely + * received. + */ + struct homa_ack acks[HOMA_MAX_ACKS_PER_PKT]; + + /** + * @ack_lock: used to synchronize access to @num_acks and @acks. + */ + spinlock_t ack_lock; +}; + +void homa_dst_refresh(struct homa_peertab *peertab, + struct homa_peer *peer, + struct homa_sock *hsk); +void homa_peertab_destroy(struct homa_peertab *peertab); +int homa_peertab_init(struct homa_peertab *peertab); +void homa_peer_add_ack(struct homa_rpc *rpc); +struct homa_peer *homa_peer_find(struct homa_peertab *peertab, + const struct in6_addr *addr, + struct inet_sock *inet); +int homa_peer_get_acks(struct homa_peer *peer, int count, + struct homa_ack *dst); +struct dst_entry *homa_peer_get_dst(struct homa_peer *peer, + struct inet_sock *inet); +void homa_peer_lock_slow(struct homa_peer *peer); +void homa_peertab_gc_dsts(struct homa_peertab *peertab, __u64 now); + +/** + * homa_peer_lock() - Acquire the lock for a peer's @unacked_lock. If the lock + * isn't immediately available, record stats on the waiting time. + * @peer: Peer to lock. + */ +// static inline void homa_peer_lock(struct homa_peer *peer) +// __acquires(&peer->ack_lock) +// { +// if (!spin_trylock_bh(&peer->ack_lock)) +// homa_peer_lock_slow(peer); +// } +#define homa_peer_lock(peer) do { \ + struct homa_peer *_peer = peer; \ + if (!spin_trylock_bh(&_peer->ack_lock)) \ + homa_peer_lock_slow(_peer); \ +} while (0) + +/** + * homa_peer_unlock() - Release the lock for a peer's @unacked_lock. + * @peer: Peer to lock. + */ +static inline void homa_peer_unlock(struct homa_peer *peer) + __releases(&peer->ack_lock) +{ + spin_unlock_bh(&peer->ack_lock); +} + +/** + * homa_get_dst() - Returns destination information associated with a peer, + * updating it if the cached information is stale. + * @peer: Peer whose destination information is desired. + * @hsk: Homa socket; needed by lower-level code to recreate the dst. + * Return Up-to-date destination for peer. + */ +static inline struct dst_entry *homa_get_dst(struct homa_peer *peer, + struct homa_sock *hsk) +{ + if (unlikely(peer->dst->obsolete > 0)) + homa_dst_refresh(hsk->homa->peers, peer, hsk); + return peer->dst; +} + +#endif /* _HOMA_PEER_H */