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openvswitch: Use nested-BH locking for ovs_pcpu_storage

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ovs_pcpu_storage is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.
The data structure can be referenced recursive and there is a recursion
counter to avoid too many recursions.

Add a local_lock_t to the data structure and use
local_lock_nested_bh() for locking. Add an owner of the struct which is
the current task and acquire the lock only if the structure is not owned
by the current task.

Cc: Aaron Conole <aconole@redhat.com>
Cc: Eelco Chaudron <echaudro@redhat.com>
Cc: Ilya Maximets <i.maximets@ovn.org>
Cc: dev@openvswitch.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20250512092736.229935-9-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Sebastian Andrzej Siewior
2025-05-15 15:23:31 +02:00
committed by Paolo Abeni
parent 035fcdc4d2
commit 672318331b
3 changed files with 59 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/openvswitch/actions.c
+2 -29
View File
@@ -39,15 +39,6 @@
#include "flow_netlink.h"
#include "openvswitch_trace.h"
struct deferred_action {
struct sk_buff *skb;
const struct nlattr *actions;
int actions_len;
/* Store pkt_key clone when creating deferred action. */
struct sw_flow_key pkt_key;
};
#define MAX_L2_LEN (VLAN_ETH_HLEN + 3 * MPLS_HLEN)
struct ovs_frag_data {
unsigned long dst;
@@ -64,28 +55,10 @@ struct ovs_frag_data {
static DEFINE_PER_CPU(struct ovs_frag_data, ovs_frag_data_storage);
#define DEFERRED_ACTION_FIFO_SIZE 10
#define OVS_RECURSION_LIMIT 5
#define OVS_DEFERRED_ACTION_THRESHOLD (OVS_RECURSION_LIMIT - 2)
struct action_fifo {
int head;
int tail;
/* Deferred action fifo queue storage. */
struct deferred_action fifo[DEFERRED_ACTION_FIFO_SIZE];
DEFINE_PER_CPU(struct ovs_pcpu_storage, ovs_pcpu_storage) = {
.bh_lock = INIT_LOCAL_LOCK(bh_lock),
};
struct action_flow_keys {
struct sw_flow_key key[OVS_DEFERRED_ACTION_THRESHOLD];
};
struct ovs_pcpu_storage {
struct action_fifo action_fifos;
struct action_flow_keys flow_keys;
int exec_level;
};
static DEFINE_PER_CPU(struct ovs_pcpu_storage, ovs_pcpu_storage);
/* Make a clone of the 'key', using the pre-allocated percpu 'flow_keys'
* space. Return NULL if out of key spaces.
*/
net/openvswitch/datapath.c
+24
View File
@@ -244,11 +244,13 @@ void ovs_dp_detach_port(struct vport *p)
/* Must be called with rcu_read_lock. */
void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key)
{
struct ovs_pcpu_storage *ovs_pcpu = this_cpu_ptr(&ovs_pcpu_storage);
const struct vport *p = OVS_CB(skb)->input_vport;
struct datapath *dp = p->dp;
struct sw_flow *flow;
struct sw_flow_actions *sf_acts;
struct dp_stats_percpu *stats;
bool ovs_pcpu_locked = false;
u64 *stats_counter;
u32 n_mask_hit;
u32 n_cache_hit;
@@ -290,10 +292,26 @@ void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key)
ovs_flow_stats_update(flow, key->tp.flags, skb);
sf_acts = rcu_dereference(flow->sf_acts);
/* This path can be invoked recursively: Use the current task to
* identify recursive invocation - the lock must be acquired only once.
* Even with disabled bottom halves this can be preempted on PREEMPT_RT.
* Limit the locking to RT to avoid assigning `owner' if it can be
* avoided.
*/
if (IS_ENABLED(CONFIG_PREEMPT_RT) && ovs_pcpu->owner != current) {
local_lock_nested_bh(&ovs_pcpu_storage.bh_lock);
ovs_pcpu->owner = current;
ovs_pcpu_locked = true;
}
error = ovs_execute_actions(dp, skb, sf_acts, key);
if (unlikely(error))
net_dbg_ratelimited("ovs: action execution error on datapath %s: %d\n",
ovs_dp_name(dp), error);
if (ovs_pcpu_locked) {
ovs_pcpu->owner = NULL;
local_unlock_nested_bh(&ovs_pcpu_storage.bh_lock);
}
stats_counter = &stats->n_hit;
@@ -671,7 +689,13 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
sf_acts = rcu_dereference(flow->sf_acts);
local_bh_disable();
local_lock_nested_bh(&ovs_pcpu_storage.bh_lock);
if (IS_ENABLED(CONFIG_PREEMPT_RT))
this_cpu_write(ovs_pcpu_storage.owner, current);
err = ovs_execute_actions(dp, packet, sf_acts, &flow->key);
if (IS_ENABLED(CONFIG_PREEMPT_RT))
this_cpu_write(ovs_pcpu_storage.owner, NULL);
local_unlock_nested_bh(&ovs_pcpu_storage.bh_lock);
local_bh_enable();
rcu_read_unlock();
net/openvswitch/datapath.h
+33
View File
@@ -173,6 +173,39 @@ struct ovs_net {
bool xt_label;
};
struct deferred_action {
struct sk_buff *skb;
const struct nlattr *actions;
int actions_len;
/* Store pkt_key clone when creating deferred action. */
struct sw_flow_key pkt_key;
};
#define DEFERRED_ACTION_FIFO_SIZE 10
#define OVS_RECURSION_LIMIT 5
#define OVS_DEFERRED_ACTION_THRESHOLD (OVS_RECURSION_LIMIT - 2)
struct action_fifo {
int head;
int tail;
/* Deferred action fifo queue storage. */
struct deferred_action fifo[DEFERRED_ACTION_FIFO_SIZE];
};
struct action_flow_keys {
struct sw_flow_key key[OVS_DEFERRED_ACTION_THRESHOLD];
};
struct ovs_pcpu_storage {
struct action_fifo action_fifos;
struct action_flow_keys flow_keys;
int exec_level;
struct task_struct *owner;
local_lock_t bh_lock;
};
DECLARE_PER_CPU(struct ovs_pcpu_storage, ovs_pcpu_storage);
/**
* enum ovs_pkt_hash_types - hash info to include with a packet
* to send to userspace.