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/queueing.h | 204 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 204 insertions(+) create mode 100644 drivers/net/wireguard/queueing.h (limited to 'drivers/net/wireguard/queueing.h') diff --git a/drivers/net/wireguard/queueing.h b/drivers/net/wireguard/queueing.h new file mode 100644 index 000000000..79b6d70de --- /dev/null +++ b/drivers/net/wireguard/queueing.h @@ -0,0 +1,204 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2015-2019 Jason A. Donenfeld . All Rights Reserved. + */ + +#ifndef _WG_QUEUEING_H +#define _WG_QUEUEING_H + +#include "peer.h" +#include +#include +#include +#include +#include + +struct wg_device; +struct wg_peer; +struct multicore_worker; +struct crypt_queue; +struct prev_queue; +struct sk_buff; + +/* queueing.c APIs: */ +int wg_packet_queue_init(struct crypt_queue *queue, work_func_t function, + unsigned int len); +void wg_packet_queue_free(struct crypt_queue *queue, bool purge); +struct multicore_worker __percpu * +wg_packet_percpu_multicore_worker_alloc(work_func_t function, void *ptr); + +/* receive.c APIs: */ +void wg_packet_receive(struct wg_device *wg, struct sk_buff *skb); +void wg_packet_handshake_receive_worker(struct work_struct *work); +/* NAPI poll function: */ +int wg_packet_rx_poll(struct napi_struct *napi, int budget); +/* Workqueue worker: */ +void wg_packet_decrypt_worker(struct work_struct *work); + +/* send.c APIs: */ +void wg_packet_send_queued_handshake_initiation(struct wg_peer *peer, + bool is_retry); +void wg_packet_send_handshake_response(struct wg_peer *peer); +void wg_packet_send_handshake_cookie(struct wg_device *wg, + struct sk_buff *initiating_skb, + __le32 sender_index); +void wg_packet_send_keepalive(struct wg_peer *peer); +void wg_packet_purge_staged_packets(struct wg_peer *peer); +void wg_packet_send_staged_packets(struct wg_peer *peer); +/* Workqueue workers: */ +void wg_packet_handshake_send_worker(struct work_struct *work); +void wg_packet_tx_worker(struct work_struct *work); +void wg_packet_encrypt_worker(struct work_struct *work); + +enum packet_state { + PACKET_STATE_UNCRYPTED, + PACKET_STATE_CRYPTED, + PACKET_STATE_DEAD +}; + +struct packet_cb { + u64 nonce; + struct noise_keypair *keypair; + atomic_t state; + u32 mtu; + u8 ds; +}; + +#define PACKET_CB(skb) ((struct packet_cb *)((skb)->cb)) +#define PACKET_PEER(skb) (PACKET_CB(skb)->keypair->entry.peer) + +static inline bool wg_check_packet_protocol(struct sk_buff *skb) +{ + __be16 real_protocol = ip_tunnel_parse_protocol(skb); + return real_protocol && skb->protocol == real_protocol; +} + +static inline void wg_reset_packet(struct sk_buff *skb, bool encapsulating) +{ + u8 l4_hash = skb->l4_hash; + u8 sw_hash = skb->sw_hash; + u32 hash = skb->hash; + skb_scrub_packet(skb, true); + memset(&skb->headers, 0, sizeof(skb->headers)); + if (encapsulating) { + skb->l4_hash = l4_hash; + skb->sw_hash = sw_hash; + skb->hash = hash; + } + skb->queue_mapping = 0; + skb->nohdr = 0; + skb->peeked = 0; + skb->mac_len = 0; + skb->dev = NULL; +#ifdef CONFIG_NET_SCHED + skb->tc_index = 0; +#endif + skb_reset_redirect(skb); + skb->hdr_len = skb_headroom(skb); + skb_reset_mac_header(skb); + skb_reset_network_header(skb); + skb_reset_transport_header(skb); + skb_probe_transport_header(skb); + skb_reset_inner_headers(skb); +} + +static inline int wg_cpumask_choose_online(int *stored_cpu, unsigned int id) +{ + unsigned int cpu = *stored_cpu; + + while (unlikely(cpu >= nr_cpu_ids || !cpu_online(cpu))) + cpu = *stored_cpu = cpumask_nth(id % num_online_cpus(), cpu_online_mask); + + return cpu; +} + +/* This function is racy, in the sense that it's called while last_cpu is + * unlocked, so it could return the same CPU twice. Adding locking or using + * atomic sequence numbers is slower though, and the consequences of racing are + * harmless, so live with it. + */ +static inline int wg_cpumask_next_online(int *last_cpu) +{ + int cpu = cpumask_next(READ_ONCE(*last_cpu), cpu_online_mask); + if (cpu >= nr_cpu_ids) + cpu = cpumask_first(cpu_online_mask); + WRITE_ONCE(*last_cpu, cpu); + return cpu; +} + +void wg_prev_queue_init(struct prev_queue *queue); + +/* Multi producer */ +bool wg_prev_queue_enqueue(struct prev_queue *queue, struct sk_buff *skb); + +/* Single consumer */ +struct sk_buff *wg_prev_queue_dequeue(struct prev_queue *queue); + +/* Single consumer */ +static inline struct sk_buff *wg_prev_queue_peek(struct prev_queue *queue) +{ + if (queue->peeked) + return queue->peeked; + queue->peeked = wg_prev_queue_dequeue(queue); + return queue->peeked; +} + +/* Single consumer */ +static inline void wg_prev_queue_drop_peeked(struct prev_queue *queue) +{ + queue->peeked = NULL; +} + +static inline int wg_queue_enqueue_per_device_and_peer( + struct crypt_queue *device_queue, struct prev_queue *peer_queue, + struct sk_buff *skb, struct workqueue_struct *wq) +{ + int cpu; + + atomic_set_release(&PACKET_CB(skb)->state, PACKET_STATE_UNCRYPTED); + /* We first queue this up for the peer ingestion, but the consumer + * will wait for the state to change to CRYPTED or DEAD before. + */ + if (unlikely(!wg_prev_queue_enqueue(peer_queue, skb))) + return -ENOSPC; + + /* Then we queue it up in the device queue, which consumes the + * packet as soon as it can. + */ + cpu = wg_cpumask_next_online(&device_queue->last_cpu); + if (unlikely(ptr_ring_produce_bh(&device_queue->ring, skb))) + return -EPIPE; + queue_work_on(cpu, wq, &per_cpu_ptr(device_queue->worker, cpu)->work); + return 0; +} + +static inline void wg_queue_enqueue_per_peer_tx(struct sk_buff *skb, enum packet_state state) +{ + /* We take a reference, because as soon as we call atomic_set, the + * peer can be freed from below us. + */ + struct wg_peer *peer = wg_peer_get(PACKET_PEER(skb)); + + atomic_set_release(&PACKET_CB(skb)->state, state); + queue_work_on(wg_cpumask_choose_online(&peer->serial_work_cpu, peer->internal_id), + peer->device->packet_crypt_wq, &peer->transmit_packet_work); + wg_peer_put(peer); +} + +static inline void wg_queue_enqueue_per_peer_rx(struct sk_buff *skb, enum packet_state state) +{ + /* We take a reference, because as soon as we call atomic_set, the + * peer can be freed from below us. + */ + struct wg_peer *peer = wg_peer_get(PACKET_PEER(skb)); + + atomic_set_release(&PACKET_CB(skb)->state, state); + napi_schedule(&peer->napi); + wg_peer_put(peer); +} + +#ifdef DEBUG +bool wg_packet_counter_selftest(void); +#endif + +#endif /* _WG_QUEUEING_H */ -- cgit v1.3.1