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/pcspkr.c | 134 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 134 insertions(+) create mode 100644 drivers/input/misc/pcspkr.c (limited to 'drivers/input/misc/pcspkr.c') diff --git a/drivers/input/misc/pcspkr.c b/drivers/input/misc/pcspkr.c new file mode 100644 index 000000000..046780840 --- /dev/null +++ b/drivers/input/misc/pcspkr.c @@ -0,0 +1,134 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * PC Speaker beeper driver for Linux + * + * Copyright (c) 2002 Vojtech Pavlik + * Copyright (c) 1992 Orest Zborowski + */ + + +#include +#include +#include +#include +#include +#include +#include + +MODULE_AUTHOR("Vojtech Pavlik "); +MODULE_DESCRIPTION("PC Speaker beeper driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:pcspkr"); + +static int pcspkr_event(struct input_dev *dev, unsigned int type, + unsigned int code, int value) +{ + unsigned int count = 0; + unsigned long flags; + + if (type != EV_SND) + return -EINVAL; + + switch (code) { + case SND_BELL: + if (value) + value = 1000; + break; + case SND_TONE: + break; + default: + return -EINVAL; + } + + if (value > 20 && value < 32767) + count = PIT_TICK_RATE / value; + + raw_spin_lock_irqsave(&i8253_lock, flags); + + if (count) { + /* set command for counter 2, 2 byte write */ + outb_p(0xB6, 0x43); + /* select desired HZ */ + outb_p(count & 0xff, 0x42); + outb((count >> 8) & 0xff, 0x42); + /* enable counter 2 */ + outb_p(inb_p(0x61) | 3, 0x61); + } else { + /* disable counter 2 */ + outb(inb_p(0x61) & 0xFC, 0x61); + } + + raw_spin_unlock_irqrestore(&i8253_lock, flags); + + return 0; +} + +static int pcspkr_probe(struct platform_device *dev) +{ + struct input_dev *pcspkr_dev; + int err; + + pcspkr_dev = input_allocate_device(); + if (!pcspkr_dev) + return -ENOMEM; + + pcspkr_dev->name = "PC Speaker"; + pcspkr_dev->phys = "isa0061/input0"; + pcspkr_dev->id.bustype = BUS_ISA; + pcspkr_dev->id.vendor = 0x001f; + pcspkr_dev->id.product = 0x0001; + pcspkr_dev->id.version = 0x0100; + pcspkr_dev->dev.parent = &dev->dev; + + pcspkr_dev->evbit[0] = BIT_MASK(EV_SND); + pcspkr_dev->sndbit[0] = BIT_MASK(SND_BELL) | BIT_MASK(SND_TONE); + pcspkr_dev->event = pcspkr_event; + + err = input_register_device(pcspkr_dev); + if (err) { + input_free_device(pcspkr_dev); + return err; + } + + platform_set_drvdata(dev, pcspkr_dev); + + return 0; +} + +static void pcspkr_remove(struct platform_device *dev) +{ + struct input_dev *pcspkr_dev = platform_get_drvdata(dev); + + input_unregister_device(pcspkr_dev); + /* turn off the speaker */ + pcspkr_event(NULL, EV_SND, SND_BELL, 0); +} + +static int pcspkr_suspend(struct device *dev) +{ + pcspkr_event(NULL, EV_SND, SND_BELL, 0); + + return 0; +} + +static void pcspkr_shutdown(struct platform_device *dev) +{ + /* turn off the speaker */ + pcspkr_event(NULL, EV_SND, SND_BELL, 0); +} + +static const struct dev_pm_ops pcspkr_pm_ops = { + .suspend = pcspkr_suspend, +}; + +static struct platform_driver pcspkr_platform_driver = { + .driver = { + .name = "pcspkr", + .pm = &pcspkr_pm_ops, + }, + .probe = pcspkr_probe, + .remove = pcspkr_remove, + .shutdown = pcspkr_shutdown, +}; +module_platform_driver(pcspkr_platform_driver); + -- cgit v1.3.1