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/packet/internal.h | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 net/packet/internal.h (limited to 'net/packet/internal.h') diff --git a/net/packet/internal.h b/net/packet/internal.h new file mode 100644 index 000000000..f5c8cd0ee --- /dev/null +++ b/net/packet/internal.h @@ -0,0 +1,159 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __PACKET_INTERNAL_H__ +#define __PACKET_INTERNAL_H__ + +#include + +struct packet_mclist { + struct packet_mclist *next; + int ifindex; + int count; + unsigned short type; + unsigned short alen; + unsigned char addr[MAX_ADDR_LEN]; + struct list_head remove_list; +}; + +/* kbdq - kernel block descriptor queue */ +struct tpacket_kbdq_core { + struct pgv *pkbdq; + unsigned int feature_req_word; + unsigned int hdrlen; + unsigned char reset_pending_on_curr_blk; + unsigned short kactive_blk_num; + unsigned int blk_sizeof_priv; + + unsigned short version; + + char *pkblk_start; + char *pkblk_end; + int kblk_size; + unsigned int max_frame_len; + unsigned int knum_blocks; + uint64_t knxt_seq_num; + char *prev; + char *nxt_offset; + + struct sk_buff *skb; + + rwlock_t blk_fill_in_prog_lock; + + /* Default is set to 8ms */ +#define DEFAULT_PRB_RETIRE_TOV (8) + + ktime_t interval_ktime; + + /* timer to retire an outstanding block */ + struct hrtimer retire_blk_timer; +}; + +struct pgv { + char *buffer; +}; + +struct packet_ring_buffer { + struct pgv *pg_vec; + + unsigned int head; + unsigned int frames_per_block; + unsigned int frame_size; + unsigned int frame_max; + + unsigned int pg_vec_order; + unsigned int pg_vec_pages; + unsigned int pg_vec_len; + + unsigned int __percpu *pending_refcnt; + + union { + unsigned long *rx_owner_map; + struct tpacket_kbdq_core prb_bdqc; + }; +}; + +extern struct mutex fanout_mutex; +#define PACKET_FANOUT_MAX (1 << 16) + +struct packet_fanout { + possible_net_t net; + unsigned int num_members; + u32 max_num_members; + u16 id; + u8 type; + u8 flags; + union { + atomic_t rr_cur; + struct bpf_prog __rcu *bpf_prog; + }; + struct list_head list; + spinlock_t lock; + refcount_t sk_ref; + struct packet_type prot_hook ____cacheline_aligned_in_smp; + struct sock __rcu *arr[] __counted_by(max_num_members); +}; + +struct packet_rollover { + int sock; + atomic_long_t num; + atomic_long_t num_huge; + atomic_long_t num_failed; +#define ROLLOVER_HLEN (L1_CACHE_BYTES / sizeof(u32)) + u32 history[ROLLOVER_HLEN] ____cacheline_aligned; +} ____cacheline_aligned_in_smp; + +struct packet_sock { + /* struct sock has to be the first member of packet_sock */ + struct sock sk; + struct packet_fanout *fanout; + union tpacket_stats_u stats; + struct packet_ring_buffer rx_ring; + struct packet_ring_buffer tx_ring; + int copy_thresh; + spinlock_t bind_lock; + struct mutex pg_vec_lock; + unsigned long flags; + int ifindex; /* bound device */ + u8 vnet_hdr_sz; + __be16 num; + struct packet_rollover *rollover; + struct packet_mclist *mclist; + atomic_long_t mapped; + enum tpacket_versions tp_version; + unsigned int tp_hdrlen; + unsigned int tp_reserve; + unsigned int tp_tstamp; + struct completion skb_completion; + struct net_device __rcu *cached_dev; + struct packet_type prot_hook ____cacheline_aligned_in_smp; + atomic_t tp_drops ____cacheline_aligned_in_smp; +}; + +#define pkt_sk(ptr) container_of_const(ptr, struct packet_sock, sk) + +enum packet_sock_flags { + PACKET_SOCK_ORIGDEV, + PACKET_SOCK_AUXDATA, + PACKET_SOCK_TX_HAS_OFF, + PACKET_SOCK_TP_LOSS, + PACKET_SOCK_RUNNING, + PACKET_SOCK_PRESSURE, + PACKET_SOCK_QDISC_BYPASS, +}; + +static inline void packet_sock_flag_set(struct packet_sock *po, + enum packet_sock_flags flag, + bool val) +{ + if (val) + set_bit(flag, &po->flags); + else + clear_bit(flag, &po->flags); +} + +static inline bool packet_sock_flag(const struct packet_sock *po, + enum packet_sock_flags flag) +{ + return test_bit(flag, &po->flags); +} + +#endif -- cgit v1.3.1