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/dsa/switch.h | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 net/dsa/switch.h (limited to 'net/dsa/switch.h') diff --git a/net/dsa/switch.h b/net/dsa/switch.h new file mode 100644 index 000000000..be0a2749c --- /dev/null +++ b/net/dsa/switch.h @@ -0,0 +1,123 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ + +#ifndef __DSA_SWITCH_H +#define __DSA_SWITCH_H + +#include + +struct netlink_ext_ack; + +enum { + DSA_NOTIFIER_AGEING_TIME, + DSA_NOTIFIER_BRIDGE_JOIN, + DSA_NOTIFIER_BRIDGE_LEAVE, + DSA_NOTIFIER_FDB_ADD, + DSA_NOTIFIER_FDB_DEL, + DSA_NOTIFIER_HOST_FDB_ADD, + DSA_NOTIFIER_HOST_FDB_DEL, + DSA_NOTIFIER_LAG_FDB_ADD, + DSA_NOTIFIER_LAG_FDB_DEL, + DSA_NOTIFIER_LAG_CHANGE, + DSA_NOTIFIER_LAG_JOIN, + DSA_NOTIFIER_LAG_LEAVE, + DSA_NOTIFIER_MDB_ADD, + DSA_NOTIFIER_MDB_DEL, + DSA_NOTIFIER_HOST_MDB_ADD, + DSA_NOTIFIER_HOST_MDB_DEL, + DSA_NOTIFIER_VLAN_ADD, + DSA_NOTIFIER_VLAN_DEL, + DSA_NOTIFIER_HOST_VLAN_ADD, + DSA_NOTIFIER_HOST_VLAN_DEL, + DSA_NOTIFIER_MTU, + DSA_NOTIFIER_TAG_PROTO, + DSA_NOTIFIER_TAG_PROTO_CONNECT, + DSA_NOTIFIER_TAG_PROTO_DISCONNECT, + DSA_NOTIFIER_TAG_8021Q_VLAN_ADD, + DSA_NOTIFIER_TAG_8021Q_VLAN_DEL, + DSA_NOTIFIER_CONDUIT_STATE_CHANGE, +}; + +/* DSA_NOTIFIER_AGEING_TIME */ +struct dsa_notifier_ageing_time_info { + unsigned int ageing_time; +}; + +/* DSA_NOTIFIER_BRIDGE_* */ +struct dsa_notifier_bridge_info { + const struct dsa_port *dp; + struct dsa_bridge bridge; + bool tx_fwd_offload; + struct netlink_ext_ack *extack; +}; + +/* DSA_NOTIFIER_FDB_* */ +struct dsa_notifier_fdb_info { + const struct dsa_port *dp; + const unsigned char *addr; + u16 vid; + struct dsa_db db; +}; + +/* DSA_NOTIFIER_LAG_FDB_* */ +struct dsa_notifier_lag_fdb_info { + struct dsa_lag *lag; + const unsigned char *addr; + u16 vid; + struct dsa_db db; +}; + +/* DSA_NOTIFIER_MDB_* */ +struct dsa_notifier_mdb_info { + const struct dsa_port *dp; + const struct switchdev_obj_port_mdb *mdb; + struct dsa_db db; +}; + +/* DSA_NOTIFIER_LAG_* */ +struct dsa_notifier_lag_info { + const struct dsa_port *dp; + struct dsa_lag lag; + struct netdev_lag_upper_info *info; + struct netlink_ext_ack *extack; +}; + +/* DSA_NOTIFIER_VLAN_* */ +struct dsa_notifier_vlan_info { + const struct dsa_port *dp; + const struct switchdev_obj_port_vlan *vlan; + struct netlink_ext_ack *extack; +}; + +/* DSA_NOTIFIER_MTU */ +struct dsa_notifier_mtu_info { + const struct dsa_port *dp; + int mtu; +}; + +/* DSA_NOTIFIER_TAG_PROTO_* */ +struct dsa_notifier_tag_proto_info { + const struct dsa_device_ops *tag_ops; +}; + +/* DSA_NOTIFIER_TAG_8021Q_VLAN_* */ +struct dsa_notifier_tag_8021q_vlan_info { + const struct dsa_port *dp; + u16 vid; +}; + +/* DSA_NOTIFIER_CONDUIT_STATE_CHANGE */ +struct dsa_notifier_conduit_state_info { + const struct net_device *conduit; + bool operational; +}; + +struct dsa_vlan *dsa_vlan_find(struct list_head *vlan_list, + const struct switchdev_obj_port_vlan *vlan); + +int dsa_tree_notify(struct dsa_switch_tree *dst, unsigned long e, void *v); +int dsa_broadcast(unsigned long e, void *v); + +int dsa_switch_register_notifier(struct dsa_switch *ds); +void dsa_switch_unregister_notifier(struct dsa_switch *ds); + +#endif -- cgit v1.3.1