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 --- drivers/input/misc/gpio-beeper.c | 114 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) create mode 100644 drivers/input/misc/gpio-beeper.c (limited to 'drivers/input/misc/gpio-beeper.c') diff --git a/drivers/input/misc/gpio-beeper.c b/drivers/input/misc/gpio-beeper.c new file mode 100644 index 000000000..3d65cb4f4 --- /dev/null +++ b/drivers/input/misc/gpio-beeper.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Generic GPIO beeper driver + * + * Copyright (C) 2013-2014 Alexander Shiyan + */ + +#include +#include +#include +#include +#include +#include + +#define BEEPER_MODNAME "gpio-beeper" + +struct gpio_beeper { + struct work_struct work; + struct gpio_desc *desc; + bool beeping; +}; + +static void gpio_beeper_toggle(struct gpio_beeper *beep, bool on) +{ + gpiod_set_value_cansleep(beep->desc, on); +} + +static void gpio_beeper_work(struct work_struct *work) +{ + struct gpio_beeper *beep = container_of(work, struct gpio_beeper, work); + + gpio_beeper_toggle(beep, beep->beeping); +} + +static int gpio_beeper_event(struct input_dev *dev, unsigned int type, + unsigned int code, int value) +{ + struct gpio_beeper *beep = input_get_drvdata(dev); + + if (type != EV_SND || code != SND_BELL) + return -ENOTSUPP; + + if (value < 0) + return -EINVAL; + + beep->beeping = value; + /* Schedule work to actually turn the beeper on or off */ + schedule_work(&beep->work); + + return 0; +} + +static void gpio_beeper_close(struct input_dev *input) +{ + struct gpio_beeper *beep = input_get_drvdata(input); + + cancel_work_sync(&beep->work); + gpio_beeper_toggle(beep, false); +} + +static int gpio_beeper_probe(struct platform_device *pdev) +{ + struct gpio_beeper *beep; + struct input_dev *input; + + beep = devm_kzalloc(&pdev->dev, sizeof(*beep), GFP_KERNEL); + if (!beep) + return -ENOMEM; + + beep->desc = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW); + if (IS_ERR(beep->desc)) + return PTR_ERR(beep->desc); + + input = devm_input_allocate_device(&pdev->dev); + if (!input) + return -ENOMEM; + + INIT_WORK(&beep->work, gpio_beeper_work); + + input->name = pdev->name; + input->id.bustype = BUS_HOST; + input->id.vendor = 0x0001; + input->id.product = 0x0001; + input->id.version = 0x0100; + input->close = gpio_beeper_close; + input->event = gpio_beeper_event; + + input_set_capability(input, EV_SND, SND_BELL); + + input_set_drvdata(input, beep); + + return input_register_device(input); +} + +#ifdef CONFIG_OF +static const struct of_device_id gpio_beeper_of_match[] = { + { .compatible = "gpio-beeper", }, + { } +}; +MODULE_DEVICE_TABLE(of, gpio_beeper_of_match); +#endif + +static struct platform_driver gpio_beeper_platform_driver = { + .driver = { + .name = BEEPER_MODNAME, + .of_match_table = of_match_ptr(gpio_beeper_of_match), + }, + .probe = gpio_beeper_probe, +}; +module_platform_driver(gpio_beeper_platform_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Alexander Shiyan "); +MODULE_DESCRIPTION("Generic GPIO beeper driver"); -- cgit v1.3.1