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 --- include/net/ping.h | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 include/net/ping.h (limited to 'include/net/ping.h') diff --git a/include/net/ping.h b/include/net/ping.h new file mode 100644 index 000000000..bcbdb5a13 --- /dev/null +++ b/include/net/ping.h @@ -0,0 +1,85 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * INET An implementation of the TCP/IP protocol suite for the LINUX + * operating system. INET is implemented using the BSD Socket + * interface as the means of communication with the user level. + * + * Definitions for the "ping" module. + */ +#ifndef _PING_H +#define _PING_H + +#include +#include + +/* PING_HTABLE_SIZE must be power of 2 */ +#define PING_HTABLE_SIZE 64 +#define PING_HTABLE_MASK (PING_HTABLE_SIZE-1) + +#define GID_T_MAX (((gid_t)~0U) - 1) + +/* Compatibility glue so we can support IPv6 when it's compiled as a module */ +struct pingv6_ops { + int (*ipv6_recv_error)(struct sock *sk, struct msghdr *msg, int len); + void (*ip6_datagram_recv_common_ctl)(struct sock *sk, + struct msghdr *msg, + struct sk_buff *skb); + void (*ip6_datagram_recv_specific_ctl)(struct sock *sk, + struct msghdr *msg, + struct sk_buff *skb); + int (*icmpv6_err_convert)(u8 type, u8 code, int *err); + void (*ipv6_icmp_error)(struct sock *sk, struct sk_buff *skb, int err, + __be16 port, u32 info, u8 *payload); + int (*ipv6_chk_addr)(struct net *net, const struct in6_addr *addr, + const struct net_device *dev, int strict); +}; + +struct ping_iter_state { + struct seq_net_private p; + int bucket; + sa_family_t family; +}; + +extern struct proto ping_prot; +#if IS_ENABLED(CONFIG_IPV6) +extern struct pingv6_ops pingv6_ops; +#endif + +struct pingfakehdr { + struct icmphdr icmph; + struct msghdr *msg; + sa_family_t family; + __wsum wcheck; +}; + +int ping_get_port(struct sock *sk, unsigned short ident); +void ping_unhash(struct sock *sk); + +int ping_init_sock(struct sock *sk); +void ping_close(struct sock *sk, long timeout); +int ping_bind(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len); +void ping_err(struct sk_buff *skb, int offset, u32 info); +int ping_getfrag(void *from, char *to, int offset, int fraglen, int odd, + struct sk_buff *); + +int ping_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, + int flags); +int ping_common_sendmsg(int family, struct msghdr *msg, size_t len, + void *user_icmph, size_t icmph_len); +int ping_queue_rcv_skb(struct sock *sk, struct sk_buff *skb); +enum skb_drop_reason ping_rcv(struct sk_buff *skb); + +#ifdef CONFIG_PROC_FS +void *ping_seq_start(struct seq_file *seq, loff_t *pos, sa_family_t family); +void *ping_seq_next(struct seq_file *seq, void *v, loff_t *pos); +void ping_seq_stop(struct seq_file *seq, void *v); + +int __init ping_proc_init(void); +void ping_proc_exit(void); +#endif + +void __init ping_init(void); +int __init pingv6_init(void); +void pingv6_exit(void); + +#endif /* _PING_H */ -- cgit v1.3.1