From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- net/openvswitch/conntrack.h | 108 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 108 insertions(+) create mode 100644 net/openvswitch/conntrack.h (limited to 'net/openvswitch/conntrack.h') diff --git a/net/openvswitch/conntrack.h b/net/openvswitch/conntrack.h new file mode 100644 index 000000000..ab21d032f --- /dev/null +++ b/net/openvswitch/conntrack.h @@ -0,0 +1,108 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) 2015 Nicira, Inc. + */ + +#ifndef OVS_CONNTRACK_H +#define OVS_CONNTRACK_H 1 + +#include "flow.h" + +struct ovs_conntrack_info; +struct ovs_ct_limit_info; +enum ovs_key_attr; + +#if IS_ENABLED(CONFIG_NF_CONNTRACK) +int ovs_ct_init(struct net *); +void ovs_ct_exit_start(struct net *net); +void ovs_ct_exit_finish(struct net *net); +bool ovs_ct_verify(struct net *, enum ovs_key_attr attr); +int ovs_ct_copy_action(struct net *, const struct nlattr *, + const struct sw_flow_key *, struct sw_flow_actions **, + bool log); +int ovs_ct_action_to_attr(const struct ovs_conntrack_info *, struct sk_buff *); + +int ovs_ct_execute(struct net *, struct sk_buff *, struct sw_flow_key *, + const struct ovs_conntrack_info *); +int ovs_ct_clear(struct sk_buff *skb, struct sw_flow_key *key); + +void ovs_ct_fill_key(const struct sk_buff *skb, struct sw_flow_key *key, + bool post_ct); +int ovs_ct_put_key(const struct sw_flow_key *swkey, + const struct sw_flow_key *output, struct sk_buff *skb); +void ovs_ct_free_action(const struct nlattr *a); + +#define CT_SUPPORTED_MASK (OVS_CS_F_NEW | OVS_CS_F_ESTABLISHED | \ + OVS_CS_F_RELATED | OVS_CS_F_REPLY_DIR | \ + OVS_CS_F_INVALID | OVS_CS_F_TRACKED | \ + OVS_CS_F_SRC_NAT | OVS_CS_F_DST_NAT) +#else +#include + +static inline int ovs_ct_init(struct net *net) { return 0; } + +static inline void ovs_ct_exit_start(struct net *net) { } +static inline void ovs_ct_exit_finish(struct net *net) { } + +static inline bool ovs_ct_verify(struct net *net, int attr) +{ + return false; +} + +static inline int ovs_ct_copy_action(struct net *net, const struct nlattr *nla, + const struct sw_flow_key *key, + struct sw_flow_actions **acts, bool log) +{ + return -ENOTSUPP; +} + +static inline int ovs_ct_action_to_attr(const struct ovs_conntrack_info *info, + struct sk_buff *skb) +{ + return -ENOTSUPP; +} + +static inline int ovs_ct_execute(struct net *net, struct sk_buff *skb, + struct sw_flow_key *key, + const struct ovs_conntrack_info *info) +{ + kfree_skb(skb); + return -ENOTSUPP; +} + +static inline int ovs_ct_clear(struct sk_buff *skb, + struct sw_flow_key *key) +{ + return -ENOTSUPP; +} + +static inline void ovs_ct_fill_key(const struct sk_buff *skb, + struct sw_flow_key *key, + bool post_ct) +{ + key->ct_state = 0; + key->ct_zone = 0; + key->ct.mark = 0; + memset(&key->ct.labels, 0, sizeof(key->ct.labels)); + /* Clear 'ct_orig_proto' to mark the non-existence of original + * direction key fields. + */ + key->ct_orig_proto = 0; +} + +static inline int ovs_ct_put_key(const struct sw_flow_key *swkey, + const struct sw_flow_key *output, + struct sk_buff *skb) +{ + return 0; +} + +static inline void ovs_ct_free_action(const struct nlattr *a) { } + +#define CT_SUPPORTED_MASK 0 +#endif /* CONFIG_NF_CONNTRACK */ + +#if IS_ENABLED(CONFIG_NETFILTER_CONNCOUNT) +extern struct genl_family dp_ct_limit_genl_family; +#endif +#endif /* ovs_conntrack.h */ -- cgit v1.3.1