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/sound/seq_kernel.h | 102 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) create mode 100644 include/sound/seq_kernel.h (limited to 'include/sound/seq_kernel.h') diff --git a/include/sound/seq_kernel.h b/include/sound/seq_kernel.h new file mode 100644 index 000000000..00c32eed2 --- /dev/null +++ b/include/sound/seq_kernel.h @@ -0,0 +1,102 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef __SOUND_SEQ_KERNEL_H +#define __SOUND_SEQ_KERNEL_H + +/* + * Main kernel header file for the ALSA sequencer + * Copyright (c) 1998 by Frank van de Pol + */ +#include +#include + +typedef struct snd_seq_real_time snd_seq_real_time_t; +typedef union snd_seq_timestamp snd_seq_timestamp_t; + +/* maximum number of queues */ +#define SNDRV_SEQ_MAX_QUEUES 32 + +/* max number of concurrent clients */ +#define SNDRV_SEQ_MAX_CLIENTS 192 + +/* max number of concurrent ports */ +#define SNDRV_SEQ_MAX_PORTS 254 + +/* max number of events in memory pool */ +#define SNDRV_SEQ_MAX_EVENTS 2000 + +/* default number of events in memory pool */ +#define SNDRV_SEQ_DEFAULT_EVENTS 500 + +/* max number of events in memory pool for one client (outqueue) */ +#define SNDRV_SEQ_MAX_CLIENT_EVENTS 2000 + +/* default number of events in memory pool for one client (outqueue) */ +#define SNDRV_SEQ_DEFAULT_CLIENT_EVENTS 200 + +/* max delivery path length */ +/* NOTE: this shouldn't be greater than MAX_LOCKDEP_SUBCLASSES */ +#define SNDRV_SEQ_MAX_HOPS 8 + +/* max size of event size */ +#define SNDRV_SEQ_MAX_EVENT_LEN 0x3fffffff + +/* call-backs for kernel port */ +struct snd_seq_port_callback { + struct module *owner; + void *private_data; + int (*subscribe)(void *private_data, struct snd_seq_port_subscribe *info); + int (*unsubscribe)(void *private_data, struct snd_seq_port_subscribe *info); + int (*use)(void *private_data, struct snd_seq_port_subscribe *info); + int (*unuse)(void *private_data, struct snd_seq_port_subscribe *info); + int (*event_input)(struct snd_seq_event *ev, int direct, void *private_data, int atomic, int hop); + void (*private_free)(void *private_data); + /*...*/ +}; + +/* interface for kernel client */ +__printf(3, 4) +int snd_seq_create_kernel_client(struct snd_card *card, int client_index, + const char *name_fmt, ...); +int snd_seq_delete_kernel_client(int client); +int snd_seq_kernel_client_enqueue(int client, struct snd_seq_event *ev, + struct file *file, bool blocking); +int snd_seq_kernel_client_dispatch(int client, struct snd_seq_event *ev, int atomic, int hop); +int snd_seq_kernel_client_ctl(int client, unsigned int cmd, void *arg); + +#define SNDRV_SEQ_EXT_MASK 0xc0000000 +#define SNDRV_SEQ_EXT_USRPTR 0x80000000 +#define SNDRV_SEQ_EXT_CHAINED 0x40000000 + +typedef int (*snd_seq_dump_func_t)(void *ptr, void *buf, int count); +int snd_seq_expand_var_event(const struct snd_seq_event *event, int count, char *buf, + int in_kernel, int size_aligned); +int snd_seq_expand_var_event_at(const struct snd_seq_event *event, int count, + char *buf, int offset); +int snd_seq_dump_var_event(const struct snd_seq_event *event, + snd_seq_dump_func_t func, void *private_data); + +/* size of the event packet; it can be greater than snd_seq_event size */ +static inline size_t snd_seq_event_packet_size(struct snd_seq_event *ev) +{ + if (snd_seq_ev_is_ump(ev)) + return sizeof(struct snd_seq_ump_event); + return sizeof(struct snd_seq_event); +} + +/* interface for OSS emulation */ +int snd_seq_set_queue_tempo(int client, struct snd_seq_queue_tempo *tempo); + +/* port attach/detach */ +int snd_seq_event_port_attach(int client, struct snd_seq_port_callback *pcbp, + int cap, int type, int midi_channels, int midi_voices, char *portname); +int snd_seq_event_port_detach(int client, int port); + +#ifdef CONFIG_MODULES +void snd_seq_autoload_init(void); +void snd_seq_autoload_exit(void); +#else +#define snd_seq_autoload_init() +#define snd_seq_autoload_exit() +#endif + +#endif /* __SOUND_SEQ_KERNEL_H */ -- cgit v1.3.1