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/rtc/rtc-meson-vrtc.c | 150 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 150 insertions(+) create mode 100644 drivers/rtc/rtc-meson-vrtc.c (limited to 'drivers/rtc/rtc-meson-vrtc.c') diff --git a/drivers/rtc/rtc-meson-vrtc.c b/drivers/rtc/rtc-meson-vrtc.c new file mode 100644 index 000000000..7d38258cb --- /dev/null +++ b/drivers/rtc/rtc-meson-vrtc.c @@ -0,0 +1,150 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2019 BayLibre, SAS + * Author: Neil Armstrong + * Copyright (C) 2015 Amlogic, Inc. All rights reserved. + */ +#include +#include +#include +#include +#include +#include + +struct meson_vrtc_data { + void __iomem *io_alarm; + unsigned long alarm_time; + bool enabled; +}; + +static int meson_vrtc_read_time(struct device *dev, struct rtc_time *tm) +{ + struct timespec64 time; + + dev_dbg(dev, "%s\n", __func__); + ktime_get_real_ts64(&time); + rtc_time64_to_tm(time.tv_sec, tm); + + return 0; +} + +static void meson_vrtc_set_wakeup_time(struct meson_vrtc_data *vrtc, + unsigned long time) +{ + writel_relaxed(time, vrtc->io_alarm); +} + +static int meson_vrtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm) +{ + struct meson_vrtc_data *vrtc = dev_get_drvdata(dev); + + dev_dbg(dev, "%s: alarm->enabled=%d\n", __func__, alarm->enabled); + if (alarm->enabled) + vrtc->alarm_time = rtc_tm_to_time64(&alarm->time); + else + vrtc->alarm_time = 0; + + return 0; +} + +static int meson_vrtc_alarm_irq_enable(struct device *dev, unsigned int enabled) +{ + struct meson_vrtc_data *vrtc = dev_get_drvdata(dev); + + vrtc->enabled = enabled; + return 0; +} + +static const struct rtc_class_ops meson_vrtc_ops = { + .read_time = meson_vrtc_read_time, + .set_alarm = meson_vrtc_set_alarm, + .alarm_irq_enable = meson_vrtc_alarm_irq_enable, +}; + +static int meson_vrtc_probe(struct platform_device *pdev) +{ + struct meson_vrtc_data *vrtc; + struct rtc_device *rtc; + + vrtc = devm_kzalloc(&pdev->dev, sizeof(*vrtc), GFP_KERNEL); + if (!vrtc) + return -ENOMEM; + + vrtc->io_alarm = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(vrtc->io_alarm)) + return PTR_ERR(vrtc->io_alarm); + + device_init_wakeup(&pdev->dev, true); + + platform_set_drvdata(pdev, vrtc); + + rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + rtc->ops = &meson_vrtc_ops; + return devm_rtc_register_device(rtc); +} + +static int __maybe_unused meson_vrtc_suspend(struct device *dev) +{ + struct meson_vrtc_data *vrtc = dev_get_drvdata(dev); + + dev_dbg(dev, "%s\n", __func__); + if (vrtc->alarm_time) { + unsigned long local_time; + long alarm_secs; + struct timespec64 time; + + ktime_get_real_ts64(&time); + local_time = time.tv_sec; + + dev_dbg(dev, "alarm_time = %lus, local_time=%lus\n", + vrtc->alarm_time, local_time); + alarm_secs = vrtc->alarm_time - local_time; + if (alarm_secs > 0) { + meson_vrtc_set_wakeup_time(vrtc, alarm_secs); + dev_dbg(dev, "system will wakeup in %lds.\n", + alarm_secs); + } else { + dev_err(dev, "alarm time already passed: %lds.\n", + alarm_secs); + } + } + + return 0; +} + +static int __maybe_unused meson_vrtc_resume(struct device *dev) +{ + struct meson_vrtc_data *vrtc = dev_get_drvdata(dev); + + dev_dbg(dev, "%s\n", __func__); + + vrtc->alarm_time = 0; + meson_vrtc_set_wakeup_time(vrtc, 0); + return 0; +} + +static SIMPLE_DEV_PM_OPS(meson_vrtc_pm_ops, + meson_vrtc_suspend, meson_vrtc_resume); + +static const struct of_device_id meson_vrtc_dt_match[] = { + { .compatible = "amlogic,meson-vrtc"}, + {}, +}; +MODULE_DEVICE_TABLE(of, meson_vrtc_dt_match); + +static struct platform_driver meson_vrtc_driver = { + .probe = meson_vrtc_probe, + .driver = { + .name = "meson-vrtc", + .of_match_table = meson_vrtc_dt_match, + .pm = &meson_vrtc_pm_ops, + }, +}; + +module_platform_driver(meson_vrtc_driver); + +MODULE_DESCRIPTION("Amlogic Virtual Wakeup RTC Timer driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1