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-ep93xx.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 170 insertions(+) create mode 100644 drivers/rtc/rtc-ep93xx.c (limited to 'drivers/rtc/rtc-ep93xx.c') diff --git a/drivers/rtc/rtc-ep93xx.c b/drivers/rtc/rtc-ep93xx.c new file mode 100644 index 000000000..507c9f220 --- /dev/null +++ b/drivers/rtc/rtc-ep93xx.c @@ -0,0 +1,170 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * A driver for the RTC embedded in the Cirrus Logic EP93XX processors + * Copyright (c) 2006 Tower Technologies + * + * Author: Alessandro Zummo + */ + +#include +#include +#include +#include +#include + +#define EP93XX_RTC_DATA 0x000 +#define EP93XX_RTC_MATCH 0x004 +#define EP93XX_RTC_STATUS 0x008 +#define EP93XX_RTC_STATUS_INTR BIT(0) +#define EP93XX_RTC_LOAD 0x00C +#define EP93XX_RTC_CONTROL 0x010 +#define EP93XX_RTC_CONTROL_MIE BIT(0) +#define EP93XX_RTC_SWCOMP 0x108 +#define EP93XX_RTC_SWCOMP_DEL_MASK 0x001f0000 +#define EP93XX_RTC_SWCOMP_DEL_SHIFT 16 +#define EP93XX_RTC_SWCOMP_INT_MASK 0x0000ffff +#define EP93XX_RTC_SWCOMP_INT_SHIFT 0 + +struct ep93xx_rtc { + void __iomem *mmio_base; +}; + +static int ep93xx_rtc_get_swcomp(struct device *dev, unsigned short *preload, + unsigned short *delete) +{ + struct ep93xx_rtc *ep93xx_rtc = dev_get_drvdata(dev); + unsigned long comp; + + comp = readl(ep93xx_rtc->mmio_base + EP93XX_RTC_SWCOMP); + + if (preload) + *preload = (comp & EP93XX_RTC_SWCOMP_INT_MASK) + >> EP93XX_RTC_SWCOMP_INT_SHIFT; + + if (delete) + *delete = (comp & EP93XX_RTC_SWCOMP_DEL_MASK) + >> EP93XX_RTC_SWCOMP_DEL_SHIFT; + + return 0; +} + +static int ep93xx_rtc_read_time(struct device *dev, struct rtc_time *tm) +{ + struct ep93xx_rtc *ep93xx_rtc = dev_get_drvdata(dev); + unsigned long time; + + time = readl(ep93xx_rtc->mmio_base + EP93XX_RTC_DATA); + + rtc_time64_to_tm(time, tm); + return 0; +} + +static int ep93xx_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + struct ep93xx_rtc *ep93xx_rtc = dev_get_drvdata(dev); + unsigned long secs = rtc_tm_to_time64(tm); + + writel(secs + 1, ep93xx_rtc->mmio_base + EP93XX_RTC_LOAD); + return 0; +} + +static int ep93xx_rtc_proc(struct device *dev, struct seq_file *seq) +{ + unsigned short preload, delete; + + ep93xx_rtc_get_swcomp(dev, &preload, &delete); + + seq_printf(seq, "preload\t\t: %d\n", preload); + seq_printf(seq, "delete\t\t: %d\n", delete); + + return 0; +} + +static const struct rtc_class_ops ep93xx_rtc_ops = { + .read_time = ep93xx_rtc_read_time, + .set_time = ep93xx_rtc_set_time, + .proc = ep93xx_rtc_proc, +}; + +static ssize_t comp_preload_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + unsigned short preload; + + ep93xx_rtc_get_swcomp(dev->parent, &preload, NULL); + + return sprintf(buf, "%d\n", preload); +} +static DEVICE_ATTR_RO(comp_preload); + +static ssize_t comp_delete_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + unsigned short delete; + + ep93xx_rtc_get_swcomp(dev->parent, NULL, &delete); + + return sprintf(buf, "%d\n", delete); +} +static DEVICE_ATTR_RO(comp_delete); + +static struct attribute *ep93xx_rtc_attrs[] = { + &dev_attr_comp_preload.attr, + &dev_attr_comp_delete.attr, + NULL +}; + +static const struct attribute_group ep93xx_rtc_sysfs_files = { + .attrs = ep93xx_rtc_attrs, +}; + +static int ep93xx_rtc_probe(struct platform_device *pdev) +{ + struct ep93xx_rtc *ep93xx_rtc; + struct rtc_device *rtc; + int err; + + ep93xx_rtc = devm_kzalloc(&pdev->dev, sizeof(*ep93xx_rtc), GFP_KERNEL); + if (!ep93xx_rtc) + return -ENOMEM; + + ep93xx_rtc->mmio_base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(ep93xx_rtc->mmio_base)) + return PTR_ERR(ep93xx_rtc->mmio_base); + + platform_set_drvdata(pdev, ep93xx_rtc); + + rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + rtc->ops = &ep93xx_rtc_ops; + rtc->range_max = U32_MAX; + + err = rtc_add_group(rtc, &ep93xx_rtc_sysfs_files); + if (err) + return err; + + return devm_rtc_register_device(rtc); +} + +static const struct of_device_id ep93xx_rtc_of_ids[] = { + { .compatible = "cirrus,ep9301-rtc" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, ep93xx_rtc_of_ids); + +static struct platform_driver ep93xx_rtc_driver = { + .driver = { + .name = "ep93xx-rtc", + .of_match_table = ep93xx_rtc_of_ids, + }, + .probe = ep93xx_rtc_probe, +}; + +module_platform_driver(ep93xx_rtc_driver); + +MODULE_AUTHOR("Alessandro Zummo "); +MODULE_DESCRIPTION("EP93XX RTC driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ep93xx-rtc"); -- cgit v1.3.1