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/timer.h | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) create mode 100644 include/sound/timer.h (limited to 'include/sound/timer.h') diff --git a/include/sound/timer.h b/include/sound/timer.h new file mode 100644 index 000000000..e549eab71 --- /dev/null +++ b/include/sound/timer.h @@ -0,0 +1,140 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef __SOUND_TIMER_H +#define __SOUND_TIMER_H + +/* + * Timer abstract layer + * Copyright (c) by Jaroslav Kysela , + * Abramo Bagnara + */ + +#include +#include + +#define snd_timer_chip(timer) ((timer)->private_data) + +#define SNDRV_TIMER_DEVICES 16 + +#define SNDRV_TIMER_DEV_FLG_PCM 0x10000000 + +#define SNDRV_TIMER_HW_AUTO 0x00000001 /* auto trigger is supported */ +#define SNDRV_TIMER_HW_STOP 0x00000002 /* call stop before start */ +#define SNDRV_TIMER_HW_SLAVE 0x00000004 /* only slave timer (variable resolution) */ +#define SNDRV_TIMER_HW_FIRST 0x00000008 /* first tick can be incomplete */ +#define SNDRV_TIMER_HW_WORK 0x00000010 /* timer is called from work */ + +#define SNDRV_TIMER_IFLG_SLAVE 0x00000001 +#define SNDRV_TIMER_IFLG_RUNNING 0x00000002 +#define SNDRV_TIMER_IFLG_START 0x00000004 +#define SNDRV_TIMER_IFLG_AUTO 0x00000008 /* auto restart */ +#define SNDRV_TIMER_IFLG_FAST 0x00000010 /* fast callback (do not use work) */ +#define SNDRV_TIMER_IFLG_CALLBACK 0x00000020 /* timer callback is active */ +#define SNDRV_TIMER_IFLG_EXCLUSIVE 0x00000040 /* exclusive owner - no more instances */ +#define SNDRV_TIMER_IFLG_EARLY_EVENT 0x00000080 /* write early event to the poll queue */ + +#define SNDRV_TIMER_FLG_CHANGE 0x00000001 +#define SNDRV_TIMER_FLG_RESCHED 0x00000002 /* need reschedule */ + +struct snd_timer; + +struct snd_timer_hardware { + /* -- must be filled with low-level driver */ + unsigned int flags; /* various flags */ + unsigned long resolution; /* average timer resolution for one tick in nsec */ + unsigned long resolution_min; /* minimal resolution */ + unsigned long resolution_max; /* maximal resolution */ + unsigned long ticks; /* max timer ticks per interrupt */ + /* -- low-level functions -- */ + int (*open) (struct snd_timer * timer); + int (*close) (struct snd_timer * timer); + unsigned long (*c_resolution) (struct snd_timer * timer); + int (*start) (struct snd_timer * timer); + int (*stop) (struct snd_timer * timer); + int (*set_period) (struct snd_timer * timer, unsigned long period_num, unsigned long period_den); + int (*precise_resolution) (struct snd_timer * timer, unsigned long *num, unsigned long *den); +}; + +struct snd_timer { + int tmr_class; + struct snd_card *card; + struct module *module; + int tmr_device; + int tmr_subdevice; + char id[64]; + char name[80]; + unsigned int flags; + int running; /* running instances */ + unsigned long sticks; /* schedule ticks */ + void *private_data; + void (*private_free) (struct snd_timer *timer); + struct snd_timer_hardware hw; + spinlock_t lock; + struct list_head device_list; + struct list_head open_list_head; + struct list_head active_list_head; + struct list_head ack_list_head; + struct list_head sack_list_head; /* slow ack list head */ + struct work_struct task_work; + struct kref kref; + int max_instances; /* upper limit of timer instances */ + int num_instances; /* current number of timer instances */ +}; + +struct snd_timer_instance { + struct snd_timer *timer; + char *owner; + unsigned int flags; + void *private_data; + void (*private_free) (struct snd_timer_instance *ti); + void (*callback) (struct snd_timer_instance *timeri, + unsigned long ticks, unsigned long resolution); + void (*ccallback) (struct snd_timer_instance * timeri, + int event, + struct timespec64 * tstamp, + unsigned long resolution); + void (*disconnect)(struct snd_timer_instance *timeri); + void *callback_data; + unsigned long ticks; /* auto-load ticks when expired */ + unsigned long cticks; /* current ticks */ + unsigned long pticks; /* accumulated ticks for callback */ + unsigned long resolution; /* current resolution for work */ + unsigned long lost; /* lost ticks */ + int slave_class; + unsigned int slave_id; + struct list_head open_list; + struct list_head active_list; + struct list_head master_list; + struct list_head ack_list; + struct list_head slave_list_head; + struct list_head slave_active_head; + struct snd_timer_instance *master; +}; + +/* + * Registering + */ + +int snd_timer_new(struct snd_card *card, char *id, struct snd_timer_id *tid, struct snd_timer **rtimer); +void snd_timer_notify(struct snd_timer *timer, int event, struct timespec64 *tstamp); +int snd_timer_global_new(char *id, int device, struct snd_timer **rtimer); +int snd_timer_global_free(struct snd_timer *timer); +int snd_timer_global_register(struct snd_timer *timer); + +struct snd_timer_instance *snd_timer_instance_new(const char *owner); +void snd_timer_instance_free(struct snd_timer_instance *timeri); +int snd_timer_open(struct snd_timer_instance *timeri, struct snd_timer_id *tid, unsigned int slave_id); +void snd_timer_close(struct snd_timer_instance *timeri); +unsigned long snd_timer_resolution(struct snd_timer_instance *timeri); +int snd_timer_start(struct snd_timer_instance *timeri, unsigned int ticks); +int snd_timer_stop(struct snd_timer_instance *timeri); +int snd_timer_continue(struct snd_timer_instance *timeri); +int snd_timer_pause(struct snd_timer_instance *timeri); + +void snd_timer_interrupt(struct snd_timer *timer, unsigned long ticks_left); + +struct snd_timer *snd_timeri_timer_get(struct snd_timer_instance *timeri); +void snd_timeri_timer_put(struct snd_timer *timer); + +DEFINE_FREE(snd_timeri_timer, struct snd_timer *, if (_T) snd_timeri_timer_put(_T)) + +#endif /* __SOUND_TIMER_H */ -- cgit v1.3.1