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 --- drivers/net/wireguard/allowedips.h | 63 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 drivers/net/wireguard/allowedips.h (limited to 'drivers/net/wireguard/allowedips.h') diff --git a/drivers/net/wireguard/allowedips.h b/drivers/net/wireguard/allowedips.h new file mode 100644 index 000000000..931958cb6 --- /dev/null +++ b/drivers/net/wireguard/allowedips.h @@ -0,0 +1,63 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2015-2019 Jason A. Donenfeld . All Rights Reserved. + */ + +#ifndef _WG_ALLOWEDIPS_H +#define _WG_ALLOWEDIPS_H + +#include +#include +#include + +struct wg_peer; + +struct allowedips_node { + struct wg_peer __rcu *peer; + struct allowedips_node __rcu *bit[2]; + u8 cidr, bit_at_a, bit_at_b, bitlen; + u8 bits[16] __aligned(__alignof(u64)); + + /* Keep rarely used members at bottom to be beyond cache line. */ + unsigned long parent_bit_packed; + union { + struct list_head peer_list; + struct rcu_head rcu; + }; +}; + +struct allowedips { + struct allowedips_node __rcu *root4; + struct allowedips_node __rcu *root6; + u64 seq; +} __aligned(4); /* We pack the lower 2 bits of &root, but m68k only gives 16-bit alignment. */ + +void wg_allowedips_init(struct allowedips *table); +void wg_allowedips_free(struct allowedips *table, struct mutex *mutex); +int wg_allowedips_insert_v4(struct allowedips *table, const struct in_addr *ip, + u8 cidr, struct wg_peer *peer, struct mutex *lock); +int wg_allowedips_insert_v6(struct allowedips *table, const struct in6_addr *ip, + u8 cidr, struct wg_peer *peer, struct mutex *lock); +int wg_allowedips_remove_v4(struct allowedips *table, const struct in_addr *ip, + u8 cidr, struct wg_peer *peer, struct mutex *lock); +int wg_allowedips_remove_v6(struct allowedips *table, const struct in6_addr *ip, + u8 cidr, struct wg_peer *peer, struct mutex *lock); +void wg_allowedips_remove_by_peer(struct allowedips *table, + struct wg_peer *peer, struct mutex *lock); +/* The ip input pointer should be __aligned(__alignof(u64))) */ +int wg_allowedips_read_node(struct allowedips_node *node, u8 ip[16], u8 *cidr); + +/* These return a strong reference to a peer: */ +struct wg_peer *wg_allowedips_lookup_dst(struct allowedips *table, + struct sk_buff *skb); +struct wg_peer *wg_allowedips_lookup_src(struct allowedips *table, + struct sk_buff *skb); + +#ifdef DEBUG +bool wg_allowedips_selftest(void); +#endif + +int wg_allowedips_slab_init(void); +void wg_allowedips_slab_uninit(void); + +#endif /* _WG_ALLOWEDIPS_H */ -- cgit v1.3.1