Files
linux/drivers/net/ethernet/netronome/nfp/flower/cmsg.c
Fred Lotter 28abe57962 nfp: flower: cmsg rtnl locks can timeout reify messages
Flower control message replies are handled in different locations. The truly
high priority replies are handled in the BH (tasklet) context, while the
remaining replies are handled in a predefined Linux work queue. The work
queue handler orders replies into high and low priority groups, and always
start servicing the high priority replies within the received batch first.

Reply Type:			Rtnl Lock:	Handler:

CMSG_TYPE_PORT_MOD		no		BH tasklet (mtu)
CMSG_TYPE_TUN_NEIGH		no		BH tasklet
CMSG_TYPE_FLOW_STATS		no		BH tasklet
CMSG_TYPE_PORT_REIFY		no		WQ high
CMSG_TYPE_PORT_MOD		yes		WQ high (link/mtu)
CMSG_TYPE_MERGE_HINT		yes		WQ low
CMSG_TYPE_NO_NEIGH		no		WQ low
CMSG_TYPE_ACTIVE_TUNS		no		WQ low
CMSG_TYPE_QOS_STATS		no		WQ low
CMSG_TYPE_LAG_CONFIG		no		WQ low

A subset of control messages can block waiting for an rtnl lock (from both
work queue priority groups). The rtnl lock is heavily contended for by
external processes such as systemd-udevd, systemd-network and libvirtd,
especially during netdev creation, such as when flower VFs and representors
are instantiated.

Kernel netlink instrumentation shows that external processes (such as
systemd-udevd) often use successive rtnl_trylock() sequences, which can result
in an rtnl_lock() blocked control message to starve for longer periods of time
during rtnl lock contention, i.e. netdev creation.

In the current design a single blocked control message will block the entire
work queue (both priorities), and introduce a latency which is
nondeterministic and dependent on system wide rtnl lock usage.

In some extreme cases, one blocked control message at exactly the wrong time,
just before the maximum number of VFs are instantiated, can block the work
queue for long enough to prevent VF representor REIFY replies from getting
handled in time for the 40ms timeout.

The firmware will deliver the total maximum number of REIFY message replies in
around 300us.

Only REIFY and MTU update messages require replies within a timeout period (of
40ms). The MTU-only updates are already done directly in the BH (tasklet)
handler.

Move the REIFY handler down into the BH (tasklet) in order to resolve timeouts
caused by a blocked work queue waiting on rtnl locks.

Signed-off-by: Fred Lotter <frederik.lotter@netronome.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-09-07 18:05:50 +02:00

375 lines
9.5 KiB
C

// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (C) 2015-2018 Netronome Systems, Inc. */
#include <linux/bitfield.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/workqueue.h>
#include <net/dst_metadata.h>
#include "main.h"
#include "../nfp_net.h"
#include "../nfp_net_repr.h"
#include "./cmsg.h"
static struct nfp_flower_cmsg_hdr *
nfp_flower_cmsg_get_hdr(struct sk_buff *skb)
{
return (struct nfp_flower_cmsg_hdr *)skb->data;
}
struct sk_buff *
nfp_flower_cmsg_alloc(struct nfp_app *app, unsigned int size,
enum nfp_flower_cmsg_type_port type, gfp_t flag)
{
struct nfp_flower_cmsg_hdr *ch;
struct sk_buff *skb;
size += NFP_FLOWER_CMSG_HLEN;
skb = nfp_app_ctrl_msg_alloc(app, size, flag);
if (!skb)
return NULL;
ch = nfp_flower_cmsg_get_hdr(skb);
ch->pad = 0;
ch->version = NFP_FLOWER_CMSG_VER1;
ch->type = type;
skb_put(skb, size);
return skb;
}
struct sk_buff *
nfp_flower_cmsg_mac_repr_start(struct nfp_app *app, unsigned int num_ports)
{
struct nfp_flower_cmsg_mac_repr *msg;
struct sk_buff *skb;
skb = nfp_flower_cmsg_alloc(app, struct_size(msg, ports, num_ports),
NFP_FLOWER_CMSG_TYPE_MAC_REPR, GFP_KERNEL);
if (!skb)
return NULL;
msg = nfp_flower_cmsg_get_data(skb);
memset(msg->reserved, 0, sizeof(msg->reserved));
msg->num_ports = num_ports;
return skb;
}
void
nfp_flower_cmsg_mac_repr_add(struct sk_buff *skb, unsigned int idx,
unsigned int nbi, unsigned int nbi_port,
unsigned int phys_port)
{
struct nfp_flower_cmsg_mac_repr *msg;
msg = nfp_flower_cmsg_get_data(skb);
msg->ports[idx].idx = idx;
msg->ports[idx].info = nbi & NFP_FLOWER_CMSG_MAC_REPR_NBI;
msg->ports[idx].nbi_port = nbi_port;
msg->ports[idx].phys_port = phys_port;
}
int nfp_flower_cmsg_portmod(struct nfp_repr *repr, bool carrier_ok,
unsigned int mtu, bool mtu_only)
{
struct nfp_flower_cmsg_portmod *msg;
struct sk_buff *skb;
skb = nfp_flower_cmsg_alloc(repr->app, sizeof(*msg),
NFP_FLOWER_CMSG_TYPE_PORT_MOD, GFP_KERNEL);
if (!skb)
return -ENOMEM;
msg = nfp_flower_cmsg_get_data(skb);
msg->portnum = cpu_to_be32(repr->dst->u.port_info.port_id);
msg->reserved = 0;
msg->info = carrier_ok;
if (mtu_only)
msg->info |= NFP_FLOWER_CMSG_PORTMOD_MTU_CHANGE_ONLY;
msg->mtu = cpu_to_be16(mtu);
nfp_ctrl_tx(repr->app->ctrl, skb);
return 0;
}
int nfp_flower_cmsg_portreify(struct nfp_repr *repr, bool exists)
{
struct nfp_flower_cmsg_portreify *msg;
struct sk_buff *skb;
skb = nfp_flower_cmsg_alloc(repr->app, sizeof(*msg),
NFP_FLOWER_CMSG_TYPE_PORT_REIFY,
GFP_KERNEL);
if (!skb)
return -ENOMEM;
msg = nfp_flower_cmsg_get_data(skb);
msg->portnum = cpu_to_be32(repr->dst->u.port_info.port_id);
msg->reserved = 0;
msg->info = cpu_to_be16(exists);
nfp_ctrl_tx(repr->app->ctrl, skb);
return 0;
}
static bool
nfp_flower_process_mtu_ack(struct nfp_app *app, struct sk_buff *skb)
{
struct nfp_flower_priv *app_priv = app->priv;
struct nfp_flower_cmsg_portmod *msg;
msg = nfp_flower_cmsg_get_data(skb);
if (!(msg->info & NFP_FLOWER_CMSG_PORTMOD_MTU_CHANGE_ONLY))
return false;
spin_lock_bh(&app_priv->mtu_conf.lock);
if (!app_priv->mtu_conf.requested_val ||
app_priv->mtu_conf.portnum != be32_to_cpu(msg->portnum) ||
be16_to_cpu(msg->mtu) != app_priv->mtu_conf.requested_val) {
/* Not an ack for requested MTU change. */
spin_unlock_bh(&app_priv->mtu_conf.lock);
return false;
}
app_priv->mtu_conf.ack = true;
app_priv->mtu_conf.requested_val = 0;
wake_up(&app_priv->mtu_conf.wait_q);
spin_unlock_bh(&app_priv->mtu_conf.lock);
return true;
}
static void
nfp_flower_cmsg_portmod_rx(struct nfp_app *app, struct sk_buff *skb)
{
struct nfp_flower_cmsg_portmod *msg;
struct net_device *netdev;
bool link;
msg = nfp_flower_cmsg_get_data(skb);
link = msg->info & NFP_FLOWER_CMSG_PORTMOD_INFO_LINK;
rtnl_lock();
rcu_read_lock();
netdev = nfp_app_dev_get(app, be32_to_cpu(msg->portnum), NULL);
rcu_read_unlock();
if (!netdev) {
nfp_flower_cmsg_warn(app, "ctrl msg for unknown port 0x%08x\n",
be32_to_cpu(msg->portnum));
rtnl_unlock();
return;
}
if (link) {
u16 mtu = be16_to_cpu(msg->mtu);
netif_carrier_on(netdev);
/* An MTU of 0 from the firmware should be ignored */
if (mtu)
dev_set_mtu(netdev, mtu);
} else {
netif_carrier_off(netdev);
}
rtnl_unlock();
}
static void
nfp_flower_cmsg_portreify_rx(struct nfp_app *app, struct sk_buff *skb)
{
struct nfp_flower_priv *priv = app->priv;
struct nfp_flower_cmsg_portreify *msg;
bool exists;
msg = nfp_flower_cmsg_get_data(skb);
rcu_read_lock();
exists = !!nfp_app_dev_get(app, be32_to_cpu(msg->portnum), NULL);
rcu_read_unlock();
if (!exists) {
nfp_flower_cmsg_warn(app, "ctrl msg for unknown port 0x%08x\n",
be32_to_cpu(msg->portnum));
return;
}
atomic_inc(&priv->reify_replies);
wake_up(&priv->reify_wait_queue);
}
static void
nfp_flower_cmsg_merge_hint_rx(struct nfp_app *app, struct sk_buff *skb)
{
unsigned int msg_len = nfp_flower_cmsg_get_data_len(skb);
struct nfp_flower_cmsg_merge_hint *msg;
struct nfp_fl_payload *sub_flows[2];
int err, i, flow_cnt;
msg = nfp_flower_cmsg_get_data(skb);
/* msg->count starts at 0 and always assumes at least 1 entry. */
flow_cnt = msg->count + 1;
if (msg_len < struct_size(msg, flow, flow_cnt)) {
nfp_flower_cmsg_warn(app, "Merge hint ctrl msg too short - %d bytes but expect %zd\n",
msg_len, struct_size(msg, flow, flow_cnt));
return;
}
if (flow_cnt != 2) {
nfp_flower_cmsg_warn(app, "Merge hint contains %d flows - two are expected\n",
flow_cnt);
return;
}
rtnl_lock();
for (i = 0; i < flow_cnt; i++) {
u32 ctx = be32_to_cpu(msg->flow[i].host_ctx);
sub_flows[i] = nfp_flower_get_fl_payload_from_ctx(app, ctx);
if (!sub_flows[i]) {
nfp_flower_cmsg_warn(app, "Invalid flow in merge hint\n");
goto err_rtnl_unlock;
}
}
err = nfp_flower_merge_offloaded_flows(app, sub_flows[0], sub_flows[1]);
/* Only warn on memory fail. Hint veto will not break functionality. */
if (err == -ENOMEM)
nfp_flower_cmsg_warn(app, "Flow merge memory fail.\n");
err_rtnl_unlock:
rtnl_unlock();
}
static void
nfp_flower_cmsg_process_one_rx(struct nfp_app *app, struct sk_buff *skb)
{
struct nfp_flower_priv *app_priv = app->priv;
struct nfp_flower_cmsg_hdr *cmsg_hdr;
enum nfp_flower_cmsg_type_port type;
bool skb_stored = false;
cmsg_hdr = nfp_flower_cmsg_get_hdr(skb);
type = cmsg_hdr->type;
switch (type) {
case NFP_FLOWER_CMSG_TYPE_PORT_MOD:
nfp_flower_cmsg_portmod_rx(app, skb);
break;
case NFP_FLOWER_CMSG_TYPE_MERGE_HINT:
if (app_priv->flower_ext_feats & NFP_FL_FEATS_FLOW_MERGE) {
nfp_flower_cmsg_merge_hint_rx(app, skb);
break;
}
goto err_default;
case NFP_FLOWER_CMSG_TYPE_NO_NEIGH:
nfp_tunnel_request_route(app, skb);
break;
case NFP_FLOWER_CMSG_TYPE_ACTIVE_TUNS:
nfp_tunnel_keep_alive(app, skb);
break;
case NFP_FLOWER_CMSG_TYPE_QOS_STATS:
nfp_flower_stats_rlim_reply(app, skb);
break;
case NFP_FLOWER_CMSG_TYPE_LAG_CONFIG:
if (app_priv->flower_ext_feats & NFP_FL_FEATS_LAG) {
skb_stored = nfp_flower_lag_unprocessed_msg(app, skb);
break;
}
/* fall through */
default:
err_default:
nfp_flower_cmsg_warn(app, "Cannot handle invalid repr control type %u\n",
type);
goto out;
}
if (!skb_stored)
dev_consume_skb_any(skb);
return;
out:
dev_kfree_skb_any(skb);
}
void nfp_flower_cmsg_process_rx(struct work_struct *work)
{
struct sk_buff_head cmsg_joined;
struct nfp_flower_priv *priv;
struct sk_buff *skb;
priv = container_of(work, struct nfp_flower_priv, cmsg_work);
skb_queue_head_init(&cmsg_joined);
spin_lock_bh(&priv->cmsg_skbs_high.lock);
skb_queue_splice_tail_init(&priv->cmsg_skbs_high, &cmsg_joined);
spin_unlock_bh(&priv->cmsg_skbs_high.lock);
spin_lock_bh(&priv->cmsg_skbs_low.lock);
skb_queue_splice_tail_init(&priv->cmsg_skbs_low, &cmsg_joined);
spin_unlock_bh(&priv->cmsg_skbs_low.lock);
while ((skb = __skb_dequeue(&cmsg_joined)))
nfp_flower_cmsg_process_one_rx(priv->app, skb);
}
static void
nfp_flower_queue_ctl_msg(struct nfp_app *app, struct sk_buff *skb, int type)
{
struct nfp_flower_priv *priv = app->priv;
struct sk_buff_head *skb_head;
if (type == NFP_FLOWER_CMSG_TYPE_PORT_MOD)
skb_head = &priv->cmsg_skbs_high;
else
skb_head = &priv->cmsg_skbs_low;
if (skb_queue_len(skb_head) >= NFP_FLOWER_WORKQ_MAX_SKBS) {
nfp_flower_cmsg_warn(app, "Dropping queued control messages\n");
dev_kfree_skb_any(skb);
return;
}
skb_queue_tail(skb_head, skb);
schedule_work(&priv->cmsg_work);
}
void nfp_flower_cmsg_rx(struct nfp_app *app, struct sk_buff *skb)
{
struct nfp_flower_cmsg_hdr *cmsg_hdr;
cmsg_hdr = nfp_flower_cmsg_get_hdr(skb);
if (unlikely(cmsg_hdr->version != NFP_FLOWER_CMSG_VER1)) {
nfp_flower_cmsg_warn(app, "Cannot handle repr control version %u\n",
cmsg_hdr->version);
dev_kfree_skb_any(skb);
return;
}
if (cmsg_hdr->type == NFP_FLOWER_CMSG_TYPE_FLOW_STATS) {
/* We need to deal with stats updates from HW asap */
nfp_flower_rx_flow_stats(app, skb);
dev_consume_skb_any(skb);
} else if (cmsg_hdr->type == NFP_FLOWER_CMSG_TYPE_PORT_MOD &&
nfp_flower_process_mtu_ack(app, skb)) {
/* Handle MTU acks outside wq to prevent RTNL conflict. */
dev_consume_skb_any(skb);
} else if (cmsg_hdr->type == NFP_FLOWER_CMSG_TYPE_TUN_NEIGH) {
/* Acks from the NFP that the route is added - ignore. */
dev_consume_skb_any(skb);
} else if (cmsg_hdr->type == NFP_FLOWER_CMSG_TYPE_PORT_REIFY) {
/* Handle REIFY acks outside wq to prevent RTNL conflict. */
nfp_flower_cmsg_portreify_rx(app, skb);
dev_consume_skb_any(skb);
} else {
nfp_flower_queue_ctl_msg(app, skb, cmsg_hdr->type);
}
}