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/ipv6/fou6.c | 226 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 226 insertions(+) create mode 100644 net/ipv6/fou6.c (limited to 'net/ipv6/fou6.c') diff --git a/net/ipv6/fou6.c b/net/ipv6/fou6.c new file mode 100644 index 000000000..4b659ca60 --- /dev/null +++ b/net/ipv6/fou6.c @@ -0,0 +1,226 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#if IS_ENABLED(CONFIG_IPV6_FOU_TUNNEL) + +static void fou6_build_udp(struct sk_buff *skb, struct ip_tunnel_encap *e, + struct flowi6 *fl6, u8 *protocol, __be16 sport) +{ + struct udphdr *uh; + + skb_push(skb, sizeof(struct udphdr)); + skb_reset_transport_header(skb); + + uh = udp_hdr(skb); + + uh->dest = e->dport; + uh->source = sport; + udp_set_len(uh, skb->len); + udp6_set_csum(!(e->flags & TUNNEL_ENCAP_FLAG_CSUM6), skb, + &fl6->saddr, &fl6->daddr, skb->len); + + *protocol = IPPROTO_UDP; +} + +static int fou6_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e, + u8 *protocol, struct flowi6 *fl6) +{ + __be16 sport; + int err; + int type = e->flags & TUNNEL_ENCAP_FLAG_CSUM6 ? + SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL; + + err = __fou_build_header(skb, e, protocol, &sport, type); + if (err) + return err; + + fou6_build_udp(skb, e, fl6, protocol, sport); + + return 0; +} + +static int gue6_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e, + u8 *protocol, struct flowi6 *fl6) +{ + __be16 sport; + int err; + int type = e->flags & TUNNEL_ENCAP_FLAG_CSUM6 ? + SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL; + + err = __gue_build_header(skb, e, protocol, &sport, type); + if (err) + return err; + + fou6_build_udp(skb, e, fl6, protocol, sport); + + return 0; +} + +static int gue6_err_proto_handler(int proto, struct sk_buff *skb, + struct inet6_skb_parm *opt, + u8 type, u8 code, int offset, __be32 info) +{ + const struct inet6_protocol *ipprot; + + ipprot = rcu_dereference(inet6_protos[proto]); + if (ipprot && ipprot->err_handler) { + if (!ipprot->err_handler(skb, opt, type, code, offset, info)) + return 0; + } + + return -ENOENT; +} + +static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, + u8 type, u8 code, int offset, __be32 info) +{ + int transport_offset = skb_transport_offset(skb); + struct guehdr *guehdr; + size_t len, optlen; + int ret; + + len = sizeof(struct udphdr) + sizeof(struct guehdr); + if (!pskb_may_pull(skb, transport_offset + len)) + return -EINVAL; + + guehdr = (struct guehdr *)&udp_hdr(skb)[1]; + + switch (guehdr->version) { + case 0: /* Full GUE header present */ + break; + case 1: { + /* Direct encasulation of IPv4 or IPv6 */ + skb_set_transport_header(skb, -(int)sizeof(struct icmp6hdr)); + + switch (((struct iphdr *)guehdr)->version) { + case 4: + ret = gue6_err_proto_handler(IPPROTO_IPIP, skb, opt, + type, code, offset, info); + goto out; + case 6: + ret = gue6_err_proto_handler(IPPROTO_IPV6, skb, opt, + type, code, offset, info); + goto out; + default: + ret = -EOPNOTSUPP; + goto out; + } + } + default: /* Undefined version */ + return -EOPNOTSUPP; + } + + if (guehdr->control) + return -ENOENT; + + optlen = guehdr->hlen << 2; + + if (!pskb_may_pull(skb, transport_offset + len + optlen)) + return -EINVAL; + + guehdr = (struct guehdr *)&udp_hdr(skb)[1]; + if (validate_gue_flags(guehdr, optlen)) + return -EINVAL; + + /* Handling exceptions for direct UDP encapsulation in GUE would lead to + * recursion. Besides, this kind of encapsulation can't even be + * configured currently. Discard this. + */ + if (guehdr->proto_ctype == IPPROTO_UDP) + return -EOPNOTSUPP; + + skb_set_transport_header(skb, -(int)sizeof(struct icmp6hdr)); + ret = gue6_err_proto_handler(guehdr->proto_ctype, skb, + opt, type, code, offset, info); + +out: + skb_set_transport_header(skb, transport_offset); + return ret; +} + + +static const struct ip6_tnl_encap_ops fou_ip6tun_ops = { + .encap_hlen = fou_encap_hlen, + .build_header = fou6_build_header, + .err_handler = gue6_err, +}; + +static const struct ip6_tnl_encap_ops gue_ip6tun_ops = { + .encap_hlen = gue_encap_hlen, + .build_header = gue6_build_header, + .err_handler = gue6_err, +}; + +static int ip6_tnl_encap_add_fou_ops(void) +{ + int ret; + + ret = ip6_tnl_encap_add_ops(&fou_ip6tun_ops, TUNNEL_ENCAP_FOU); + if (ret < 0) { + pr_err("can't add fou6 ops\n"); + return ret; + } + + ret = ip6_tnl_encap_add_ops(&gue_ip6tun_ops, TUNNEL_ENCAP_GUE); + if (ret < 0) { + pr_err("can't add gue6 ops\n"); + ip6_tnl_encap_del_ops(&fou_ip6tun_ops, TUNNEL_ENCAP_FOU); + return ret; + } + + return 0; +} + +static void ip6_tnl_encap_del_fou_ops(void) +{ + ip6_tnl_encap_del_ops(&fou_ip6tun_ops, TUNNEL_ENCAP_FOU); + ip6_tnl_encap_del_ops(&gue_ip6tun_ops, TUNNEL_ENCAP_GUE); +} + +#else + +static int ip6_tnl_encap_add_fou_ops(void) +{ + return 0; +} + +static void ip6_tnl_encap_del_fou_ops(void) +{ +} + +#endif + +static int __init fou6_init(void) +{ + int ret; + + ret = ip6_tnl_encap_add_fou_ops(); + + return ret; +} + +static void __exit fou6_fini(void) +{ + ip6_tnl_encap_del_fou_ops(); +} + +module_init(fou6_init); +module_exit(fou6_fini); +MODULE_AUTHOR("Tom Herbert "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Foo over UDP (IPv6)"); -- cgit v1.3.1