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/qnap-mcu-input.c | 153 ++++++++++++++++++++++++++++++++++++ 1 file changed, 153 insertions(+) create mode 100644 drivers/input/misc/qnap-mcu-input.c (limited to 'drivers/input/misc/qnap-mcu-input.c') diff --git a/drivers/input/misc/qnap-mcu-input.c b/drivers/input/misc/qnap-mcu-input.c new file mode 100644 index 000000000..3be899bfc --- /dev/null +++ b/drivers/input/misc/qnap-mcu-input.c @@ -0,0 +1,153 @@ +// SPDX-License-Identifier: GPL-2.0-only + +/* + * Driver for input events on QNAP-MCUs + * + * Copyright (C) 2024 Heiko Stuebner + */ + +#include +#include +#include +#include +#include +#include + +/* + * The power-key needs to be pressed for a while to create an event, + * so there is no use for overly frequent polling. + */ +#define POLL_INTERVAL 500 + +struct qnap_mcu_input_dev { + struct input_dev *input; + struct qnap_mcu *mcu; + struct device *dev; + + struct work_struct beep_work; + int beep_type; +}; + +static void qnap_mcu_input_poll(struct input_dev *input) +{ + struct qnap_mcu_input_dev *idev = input_get_drvdata(input); + static const u8 cmd[] = { '@', 'C', 'V' }; + u8 reply[4]; + int state, ret; + + /* poll the power button */ + ret = qnap_mcu_exec(idev->mcu, cmd, sizeof(cmd), reply, sizeof(reply)); + if (ret) + return; + + /* First bytes must mirror the sent command */ + if (memcmp(cmd, reply, sizeof(cmd))) { + dev_err(idev->dev, "malformed data received\n"); + return; + } + + state = reply[3] - 0x30; + input_event(input, EV_KEY, KEY_POWER, state); + input_sync(input); +} + +static void qnap_mcu_input_beeper_work(struct work_struct *work) +{ + struct qnap_mcu_input_dev *idev = + container_of(work, struct qnap_mcu_input_dev, beep_work); + const u8 cmd[] = { '@', 'C', (idev->beep_type == SND_TONE) ? '3' : '2' }; + + qnap_mcu_exec_with_ack(idev->mcu, cmd, sizeof(cmd)); +} + +static int qnap_mcu_input_event(struct input_dev *input, unsigned int type, + unsigned int code, int value) +{ + struct qnap_mcu_input_dev *idev = input_get_drvdata(input); + + if (type != EV_SND || (code != SND_BELL && code != SND_TONE)) + return -EOPNOTSUPP; + + if (value < 0) + return -EINVAL; + + /* beep runtime is determined by the MCU */ + if (value == 0) + return 0; + + /* Schedule work to actually turn the beeper on */ + idev->beep_type = code; + schedule_work(&idev->beep_work); + + return 0; +} + +static void qnap_mcu_input_close(struct input_dev *input) +{ + struct qnap_mcu_input_dev *idev = input_get_drvdata(input); + + cancel_work_sync(&idev->beep_work); +} + +static int qnap_mcu_input_probe(struct platform_device *pdev) +{ + struct qnap_mcu *mcu = dev_get_drvdata(pdev->dev.parent); + struct qnap_mcu_input_dev *idev; + struct device *dev = &pdev->dev; + struct input_dev *input; + int ret; + + idev = devm_kzalloc(dev, sizeof(*idev), GFP_KERNEL); + if (!idev) + return -ENOMEM; + + input = devm_input_allocate_device(dev); + if (!input) + return -ENOMEM; + + idev->input = input; + idev->dev = dev; + idev->mcu = mcu; + + input_set_drvdata(input, idev); + + input->name = "qnap-mcu"; + input->phys = "qnap-mcu-input/input0"; + input->id.bustype = BUS_HOST; + input->id.vendor = 0x0001; + input->id.product = 0x0001; + input->id.version = 0x0100; + input->event = qnap_mcu_input_event; + input->close = qnap_mcu_input_close; + + input_set_capability(input, EV_KEY, KEY_POWER); + input_set_capability(input, EV_SND, SND_BELL); + input_set_capability(input, EV_SND, SND_TONE); + + INIT_WORK(&idev->beep_work, qnap_mcu_input_beeper_work); + + ret = input_setup_polling(input, qnap_mcu_input_poll); + if (ret) + return dev_err_probe(dev, ret, "unable to set up polling\n"); + + input_set_poll_interval(input, POLL_INTERVAL); + + ret = input_register_device(input); + if (ret) + return dev_err_probe(dev, ret, "unable to register input device\n"); + + return 0; +} + +static struct platform_driver qnap_mcu_input_driver = { + .probe = qnap_mcu_input_probe, + .driver = { + .name = "qnap-mcu-input", + }, +}; +module_platform_driver(qnap_mcu_input_driver); + +MODULE_ALIAS("platform:qnap-mcu-input"); +MODULE_AUTHOR("Heiko Stuebner "); +MODULE_DESCRIPTION("QNAP MCU input driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1