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/l2tp/trace.h | 211 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 211 insertions(+) create mode 100644 net/l2tp/trace.h (limited to 'net/l2tp/trace.h') diff --git a/net/l2tp/trace.h b/net/l2tp/trace.h new file mode 100644 index 000000000..8596eaa12 --- /dev/null +++ b/net/l2tp/trace.h @@ -0,0 +1,211 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM l2tp + +#if !defined(_TRACE_L2TP_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_L2TP_H + +#include +#include +#include "l2tp_core.h" + +#define encap_type_name(e) { L2TP_ENCAPTYPE_##e, #e } +#define show_encap_type_name(val) \ + __print_symbolic(val, \ + encap_type_name(UDP), \ + encap_type_name(IP)) + +#define pw_type_name(p) { L2TP_PWTYPE_##p, #p } +#define show_pw_type_name(val) \ + __print_symbolic(val, \ + pw_type_name(ETH_VLAN), \ + pw_type_name(ETH), \ + pw_type_name(PPP), \ + pw_type_name(PPP_AC), \ + pw_type_name(IP)) + +DECLARE_EVENT_CLASS(tunnel_only_evt, + TP_PROTO(struct l2tp_tunnel *tunnel), + TP_ARGS(tunnel), + TP_STRUCT__entry( + __array(char, name, L2TP_TUNNEL_NAME_MAX) + ), + TP_fast_assign( + memcpy(__entry->name, tunnel->name, L2TP_TUNNEL_NAME_MAX); + ), + TP_printk("%s", __entry->name) +); + +DECLARE_EVENT_CLASS(session_only_evt, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session), + TP_STRUCT__entry( + __array(char, name, L2TP_SESSION_NAME_MAX) + ), + TP_fast_assign( + memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX); + ), + TP_printk("%s", __entry->name) +); + +TRACE_EVENT(register_tunnel, + TP_PROTO(struct l2tp_tunnel *tunnel), + TP_ARGS(tunnel), + TP_STRUCT__entry( + __array(char, name, L2TP_TUNNEL_NAME_MAX) + __field(int, fd) + __field(u32, tid) + __field(u32, ptid) + __field(int, version) + __field(enum l2tp_encap_type, encap) + ), + TP_fast_assign( + memcpy(__entry->name, tunnel->name, L2TP_TUNNEL_NAME_MAX); + __entry->fd = tunnel->fd; + __entry->tid = tunnel->tunnel_id; + __entry->ptid = tunnel->peer_tunnel_id; + __entry->version = tunnel->version; + __entry->encap = tunnel->encap; + ), + TP_printk("%s: type=%s encap=%s version=L2TPv%d tid=%u ptid=%u fd=%d", + __entry->name, + __entry->fd > 0 ? "managed" : "unmanaged", + show_encap_type_name(__entry->encap), + __entry->version, + __entry->tid, + __entry->ptid, + __entry->fd) +); + +DEFINE_EVENT(tunnel_only_evt, delete_tunnel, + TP_PROTO(struct l2tp_tunnel *tunnel), + TP_ARGS(tunnel) +); + +DEFINE_EVENT(tunnel_only_evt, free_tunnel, + TP_PROTO(struct l2tp_tunnel *tunnel), + TP_ARGS(tunnel) +); + +TRACE_EVENT(register_session, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session), + TP_STRUCT__entry( + __array(char, name, L2TP_SESSION_NAME_MAX) + __field(u32, tid) + __field(u32, ptid) + __field(u32, sid) + __field(u32, psid) + __field(enum l2tp_pwtype, pwtype) + ), + TP_fast_assign( + memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX); + __entry->tid = session->tunnel ? session->tunnel->tunnel_id : 0; + __entry->ptid = session->tunnel ? session->tunnel->peer_tunnel_id : 0; + __entry->sid = session->session_id; + __entry->psid = session->peer_session_id; + __entry->pwtype = session->pwtype; + ), + TP_printk("%s: pseudowire=%s sid=%u psid=%u tid=%u ptid=%u", + __entry->name, + show_pw_type_name(__entry->pwtype), + __entry->sid, + __entry->psid, + __entry->sid, + __entry->psid) +); + +DEFINE_EVENT(session_only_evt, delete_session, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session) +); + +DEFINE_EVENT(session_only_evt, free_session, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session) +); + +DEFINE_EVENT(session_only_evt, session_seqnum_lns_enable, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session) +); + +DEFINE_EVENT(session_only_evt, session_seqnum_lns_disable, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session) +); + +DECLARE_EVENT_CLASS(session_seqnum_evt, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session), + TP_STRUCT__entry( + __array(char, name, L2TP_SESSION_NAME_MAX) + __field(u32, ns) + __field(u32, nr) + ), + TP_fast_assign( + memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX); + __entry->ns = session->ns; + __entry->nr = session->nr; + ), + TP_printk("%s: ns=%u nr=%u", + __entry->name, + __entry->ns, + __entry->nr) +); + +DEFINE_EVENT(session_seqnum_evt, session_seqnum_update, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session) +); + +DEFINE_EVENT(session_seqnum_evt, session_seqnum_reset, + TP_PROTO(struct l2tp_session *session), + TP_ARGS(session) +); + +DECLARE_EVENT_CLASS(session_pkt_discard_evt, + TP_PROTO(struct l2tp_session *session, u32 pkt_ns), + TP_ARGS(session, pkt_ns), + TP_STRUCT__entry( + __array(char, name, L2TP_SESSION_NAME_MAX) + __field(u32, pkt_ns) + __field(u32, my_nr) + __field(u32, reorder_q_len) + ), + TP_fast_assign( + memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX); + __entry->pkt_ns = pkt_ns, + __entry->my_nr = session->nr; + __entry->reorder_q_len = skb_queue_len(&session->reorder_q); + ), + TP_printk("%s: pkt_ns=%u my_nr=%u reorder_q_len=%u", + __entry->name, + __entry->pkt_ns, + __entry->my_nr, + __entry->reorder_q_len) +); + +DEFINE_EVENT(session_pkt_discard_evt, session_pkt_expired, + TP_PROTO(struct l2tp_session *session, u32 pkt_ns), + TP_ARGS(session, pkt_ns) +); + +DEFINE_EVENT(session_pkt_discard_evt, session_pkt_outside_rx_window, + TP_PROTO(struct l2tp_session *session, u32 pkt_ns), + TP_ARGS(session, pkt_ns) +); + +DEFINE_EVENT(session_pkt_discard_evt, session_pkt_oos, + TP_PROTO(struct l2tp_session *session, u32 pkt_ns), + TP_ARGS(session, pkt_ns) +); + +#endif /* _TRACE_L2TP_H */ + +/* This part must be outside protection */ +#undef TRACE_INCLUDE_PATH +#define TRACE_INCLUDE_PATH . +#undef TRACE_INCLUDE_FILE +#define TRACE_INCLUDE_FILE trace +#include -- cgit v1.3.1