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/lapb.h | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 162 insertions(+) create mode 100644 include/net/lapb.h (limited to 'include/net/lapb.h') diff --git a/include/net/lapb.h b/include/net/lapb.h new file mode 100644 index 000000000..6c0742064 --- /dev/null +++ b/include/net/lapb.h @@ -0,0 +1,162 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LAPB_H +#define _LAPB_H +#include +#include + +#define LAPB_HEADER_LEN MAX_HEADER /* LAPB over Ethernet + a bit more */ + +#define LAPB_ACK_PENDING_CONDITION 0x01 +#define LAPB_REJECT_CONDITION 0x02 +#define LAPB_PEER_RX_BUSY_CONDITION 0x04 + +/* Control field templates */ +#define LAPB_I 0x00 /* Information frames */ +#define LAPB_S 0x01 /* Supervisory frames */ +#define LAPB_U 0x03 /* Unnumbered frames */ + +#define LAPB_RR 0x01 /* Receiver ready */ +#define LAPB_RNR 0x05 /* Receiver not ready */ +#define LAPB_REJ 0x09 /* Reject */ + +#define LAPB_SABM 0x2F /* Set Asynchronous Balanced Mode */ +#define LAPB_SABME 0x6F /* Set Asynchronous Balanced Mode Extended */ +#define LAPB_DISC 0x43 /* Disconnect */ +#define LAPB_DM 0x0F /* Disconnected mode */ +#define LAPB_UA 0x63 /* Unnumbered acknowledge */ +#define LAPB_FRMR 0x87 /* Frame reject */ + +#define LAPB_ILLEGAL 0x100 /* Impossible to be a real frame type */ + +#define LAPB_SPF 0x10 /* Poll/final bit for standard LAPB */ +#define LAPB_EPF 0x01 /* Poll/final bit for extended LAPB */ + +#define LAPB_FRMR_W 0x01 /* Control field invalid */ +#define LAPB_FRMR_X 0x02 /* I field invalid */ +#define LAPB_FRMR_Y 0x04 /* I field too long */ +#define LAPB_FRMR_Z 0x08 /* Invalid N(R) */ + +#define LAPB_POLLOFF 0 +#define LAPB_POLLON 1 + +/* LAPB C-bit */ +#define LAPB_COMMAND 1 +#define LAPB_RESPONSE 2 + +#define LAPB_ADDR_A 0x03 +#define LAPB_ADDR_B 0x01 +#define LAPB_ADDR_C 0x0F +#define LAPB_ADDR_D 0x07 + +/* Define Link State constants. */ +enum { + LAPB_STATE_0, /* Disconnected State */ + LAPB_STATE_1, /* Awaiting Connection State */ + LAPB_STATE_2, /* Awaiting Disconnection State */ + LAPB_STATE_3, /* Data Transfer State */ + LAPB_STATE_4 /* Frame Reject State */ +}; + +#define LAPB_DEFAULT_MODE (LAPB_STANDARD | LAPB_SLP | LAPB_DTE) +#define LAPB_DEFAULT_WINDOW 7 /* Window=7 */ +#define LAPB_DEFAULT_T1 (5 * HZ) /* T1=5s */ +#define LAPB_DEFAULT_T2 (1 * HZ) /* T2=1s */ +#define LAPB_DEFAULT_N2 20 /* N2=20 */ + +#define LAPB_SMODULUS 8 +#define LAPB_EMODULUS 128 + +/* + * Information about the current frame. + */ +struct lapb_frame { + unsigned short type; /* Parsed type */ + unsigned short nr, ns; /* N(R), N(S) */ + unsigned char cr; /* Command/Response */ + unsigned char pf; /* Poll/Final */ + unsigned char control[2]; /* Original control data*/ +}; + +/* + * The per LAPB connection control structure. + */ +struct lapb_cb { + struct list_head node; + struct net_device *dev; + + /* Link status fields */ + unsigned int mode; + unsigned char state; + unsigned short vs, vr, va; + unsigned char condition; + unsigned short n2, n2count; + unsigned short t1, t2; + struct timer_list t1timer, t2timer; + bool t1timer_running, t2timer_running; + + /* Internal control information */ + struct sk_buff_head write_queue; + struct sk_buff_head ack_queue; + unsigned char window; + const struct lapb_register_struct *callbacks; + + /* FRMR control information */ + struct lapb_frame frmr_data; + unsigned char frmr_type; + + spinlock_t lock; + refcount_t refcnt; +}; + +/* lapb_iface.c */ +void lapb_connect_confirmation(struct lapb_cb *lapb, int); +void lapb_connect_indication(struct lapb_cb *lapb, int); +void lapb_disconnect_confirmation(struct lapb_cb *lapb, int); +void lapb_disconnect_indication(struct lapb_cb *lapb, int); +int lapb_data_indication(struct lapb_cb *lapb, struct sk_buff *); +int lapb_data_transmit(struct lapb_cb *lapb, struct sk_buff *); + +/* lapb_in.c */ +void lapb_data_input(struct lapb_cb *lapb, struct sk_buff *); + +/* lapb_out.c */ +void lapb_kick(struct lapb_cb *lapb); +void lapb_transmit_buffer(struct lapb_cb *lapb, struct sk_buff *, int); +void lapb_establish_data_link(struct lapb_cb *lapb); +void lapb_enquiry_response(struct lapb_cb *lapb); +void lapb_timeout_response(struct lapb_cb *lapb); +void lapb_check_iframes_acked(struct lapb_cb *lapb, unsigned short); +void lapb_check_need_response(struct lapb_cb *lapb, int, int); + +/* lapb_subr.c */ +void lapb_clear_queues(struct lapb_cb *lapb); +void lapb_frames_acked(struct lapb_cb *lapb, unsigned short); +void lapb_requeue_frames(struct lapb_cb *lapb); +int lapb_validate_nr(struct lapb_cb *lapb, unsigned short); +int lapb_decode(struct lapb_cb *lapb, struct sk_buff *, struct lapb_frame *); +void lapb_send_control(struct lapb_cb *lapb, int, int, int); +void lapb_transmit_frmr(struct lapb_cb *lapb); + +/* lapb_timer.c */ +void lapb_start_t1timer(struct lapb_cb *lapb); +void lapb_start_t2timer(struct lapb_cb *lapb); +void lapb_stop_t1timer(struct lapb_cb *lapb); +void lapb_stop_t2timer(struct lapb_cb *lapb); +int lapb_t1timer_running(struct lapb_cb *lapb); + +/* + * Debug levels. + * 0 = Off + * 1 = State Changes + * 2 = Packets I/O and State Changes + * 3 = Hex dumps, Packets I/O and State Changes. + */ +#define LAPB_DEBUG 0 + +#define lapb_dbg(level, fmt, ...) \ +do { \ + if (level < LAPB_DEBUG) \ + pr_debug(fmt, ##__VA_ARGS__); \ +} while (0) + +#endif -- cgit v1.3.1