sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

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 <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 321 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-mv.c b/drivers/rtc/rtc-mv.c
new file mode 100644
index 000000000..db64c459e
--- /dev/null
+++ b/drivers/rtc/rtc-mv.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for the RTC in Marvell SoCs.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/delay.h>
+#include <linux/clk.h>
+#include <linux/gfp.h>
+#include <linux/module.h>
+
+
+#define RTC_TIME_REG_OFFS	0
+#define RTC_SECONDS_OFFS	0
+#define RTC_MINUTES_OFFS	8
+#define RTC_HOURS_OFFS		16
+#define RTC_WDAY_OFFS		24
+#define RTC_HOURS_12H_MODE	BIT(22) /* 12 hour mode */
+
+#define RTC_DATE_REG_OFFS	4
+#define RTC_MDAY_OFFS		0
+#define RTC_MONTH_OFFS		8
+#define RTC_YEAR_OFFS		16
+
+#define RTC_ALARM_TIME_REG_OFFS	8
+#define RTC_ALARM_DATE_REG_OFFS	0xc
+#define RTC_ALARM_VALID		BIT(7)
+
+#define RTC_ALARM_INTERRUPT_MASK_REG_OFFS	0x10
+#define RTC_ALARM_INTERRUPT_CASUE_REG_OFFS	0x14
+
+struct rtc_plat_data {
+	struct rtc_device *rtc;
+	void __iomem *ioaddr;
+	int		irq;
+	struct clk	*clk;
+};
+
+static int mv_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32	rtc_reg;
+
+	rtc_reg = (bin2bcd(tm->tm_sec) << RTC_SECONDS_OFFS) |
+		(bin2bcd(tm->tm_min) << RTC_MINUTES_OFFS) |
+		(bin2bcd(tm->tm_hour) << RTC_HOURS_OFFS) |
+		(bin2bcd(tm->tm_wday) << RTC_WDAY_OFFS);
+	writel(rtc_reg, ioaddr + RTC_TIME_REG_OFFS);
+
+	rtc_reg = (bin2bcd(tm->tm_mday) << RTC_MDAY_OFFS) |
+		(bin2bcd(tm->tm_mon + 1) << RTC_MONTH_OFFS) |
+		(bin2bcd(tm->tm_year - 100) << RTC_YEAR_OFFS);
+	writel(rtc_reg, ioaddr + RTC_DATE_REG_OFFS);
+
+	return 0;
+}
+
+static int mv_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32	rtc_time, rtc_date;
+	unsigned int year, month, day, hour, minute, second, wday;
+
+	rtc_time = readl(ioaddr + RTC_TIME_REG_OFFS);
+	rtc_date = readl(ioaddr + RTC_DATE_REG_OFFS);
+
+	second = rtc_time & 0x7f;
+	minute = (rtc_time >> RTC_MINUTES_OFFS) & 0x7f;
+	hour = (rtc_time >> RTC_HOURS_OFFS) & 0x3f; /* assume 24 hour mode */
+	wday = (rtc_time >> RTC_WDAY_OFFS) & 0x7;
+
+	day = rtc_date & 0x3f;
+	month = (rtc_date >> RTC_MONTH_OFFS) & 0x3f;
+	year = (rtc_date >> RTC_YEAR_OFFS) & 0xff;
+
+	tm->tm_sec = bcd2bin(second);
+	tm->tm_min = bcd2bin(minute);
+	tm->tm_hour = bcd2bin(hour);
+	tm->tm_mday = bcd2bin(day);
+	tm->tm_wday = bcd2bin(wday);
+	tm->tm_mon = bcd2bin(month) - 1;
+	/* hw counts from year 2000, but tm_year is relative to 1900 */
+	tm->tm_year = bcd2bin(year) + 100;
+
+	return 0;
+}
+
+static int mv_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32	rtc_time, rtc_date;
+	unsigned int year, month, day, hour, minute, second, wday;
+
+	rtc_time = readl(ioaddr + RTC_ALARM_TIME_REG_OFFS);
+	rtc_date = readl(ioaddr + RTC_ALARM_DATE_REG_OFFS);
+
+	second = rtc_time & 0x7f;
+	minute = (rtc_time >> RTC_MINUTES_OFFS) & 0x7f;
+	hour = (rtc_time >> RTC_HOURS_OFFS) & 0x3f; /* assume 24 hour mode */
+	wday = (rtc_time >> RTC_WDAY_OFFS) & 0x7;
+
+	day = rtc_date & 0x3f;
+	month = (rtc_date >> RTC_MONTH_OFFS) & 0x3f;
+	year = (rtc_date >> RTC_YEAR_OFFS) & 0xff;
+
+	alm->time.tm_sec = bcd2bin(second);
+	alm->time.tm_min = bcd2bin(minute);
+	alm->time.tm_hour = bcd2bin(hour);
+	alm->time.tm_mday = bcd2bin(day);
+	alm->time.tm_wday = bcd2bin(wday);
+	alm->time.tm_mon = bcd2bin(month) - 1;
+	/* hw counts from year 2000, but tm_year is relative to 1900 */
+	alm->time.tm_year = bcd2bin(year) + 100;
+
+	alm->enabled = !!readl(ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+
+	return rtc_valid_tm(&alm->time);
+}
+
+static int mv_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+	u32 rtc_reg = 0;
+
+	if (alm->time.tm_sec >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_sec))
+			<< RTC_SECONDS_OFFS;
+	if (alm->time.tm_min >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_min))
+			<< RTC_MINUTES_OFFS;
+	if (alm->time.tm_hour >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_hour))
+			<< RTC_HOURS_OFFS;
+
+	writel(rtc_reg, ioaddr + RTC_ALARM_TIME_REG_OFFS);
+
+	if (alm->time.tm_mday >= 0)
+		rtc_reg = (RTC_ALARM_VALID | bin2bcd(alm->time.tm_mday))
+			<< RTC_MDAY_OFFS;
+	else
+		rtc_reg = 0;
+
+	if (alm->time.tm_mon >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_mon + 1))
+			<< RTC_MONTH_OFFS;
+
+	if (alm->time.tm_year >= 0)
+		rtc_reg |= (RTC_ALARM_VALID | bin2bcd(alm->time.tm_year - 100))
+			<< RTC_YEAR_OFFS;
+
+	writel(rtc_reg, ioaddr + RTC_ALARM_DATE_REG_OFFS);
+	writel(0, ioaddr + RTC_ALARM_INTERRUPT_CASUE_REG_OFFS);
+	writel(alm->enabled ? 1 : 0,
+	       ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+
+	return 0;
+}
+
+static int mv_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+	void __iomem *ioaddr = pdata->ioaddr;
+
+	if (pdata->irq < 0)
+		return -EINVAL; /* fall back into rtc-dev's emulation */
+
+	if (enabled)
+		writel(1, ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+	else
+		writel(0, ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+	return 0;
+}
+
+static irqreturn_t mv_rtc_interrupt(int irq, void *data)
+{
+	struct rtc_plat_data *pdata = data;
+	void __iomem *ioaddr = pdata->ioaddr;
+
+	/* alarm irq? */
+	if (!readl(ioaddr + RTC_ALARM_INTERRUPT_CASUE_REG_OFFS))
+		return IRQ_NONE;
+
+	/* clear interrupt */
+	writel(0, ioaddr + RTC_ALARM_INTERRUPT_CASUE_REG_OFFS);
+	rtc_update_irq(pdata->rtc, 1, RTC_IRQF | RTC_AF);
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops mv_rtc_ops = {
+	.read_time	= mv_rtc_read_time,
+	.set_time	= mv_rtc_set_time,
+	.read_alarm	= mv_rtc_read_alarm,
+	.set_alarm	= mv_rtc_set_alarm,
+	.alarm_irq_enable = mv_rtc_alarm_irq_enable,
+};
+
+static int __init mv_rtc_probe(struct platform_device *pdev)
+{
+	struct rtc_plat_data *pdata;
+	u32 rtc_time;
+	int ret = 0;
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
+
+	pdata->ioaddr = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pdata->ioaddr))
+		return PTR_ERR(pdata->ioaddr);
+
+	pdata->clk = devm_clk_get_optional_prepared(&pdev->dev, NULL);
+	if (IS_ERR(pdata->clk))
+		return PTR_ERR(pdata->clk);
+
+	/* make sure the 24 hour mode is enabled */
+	rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
+	if (rtc_time & RTC_HOURS_12H_MODE) {
+		dev_err(&pdev->dev, "12 Hour mode is enabled but not supported.\n");
+		return  -EINVAL;
+	}
+
+	/* make sure it is actually functional */
+	if (rtc_time == 0x01000000) {
+		ssleep(1);
+		rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
+		if (rtc_time == 0x01000000) {
+			dev_err(&pdev->dev, "internal RTC not ticking\n");
+			return -ENODEV;
+		}
+	}
+
+	pdata->irq = platform_get_irq(pdev, 0);
+
+	platform_set_drvdata(pdev, pdata);
+
+	pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(pdata->rtc)) {
+		return PTR_ERR(pdata->rtc);
+	}
+
+	if (pdata->irq >= 0) {
+		writel(0, pdata->ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
+		if (devm_request_irq(&pdev->dev, pdata->irq, mv_rtc_interrupt,
+				     IRQF_SHARED,
+				     pdev->name, pdata) < 0) {
+			dev_warn(&pdev->dev, "interrupt not available.\n");
+			pdata->irq = -1;
+		}
+	}
+
+	if (pdata->irq >= 0)
+		devm_device_init_wakeup(&pdev->dev);
+	else
+		clear_bit(RTC_FEATURE_ALARM, pdata->rtc->features);
+
+	pdata->rtc->ops = &mv_rtc_ops;
+	pdata->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	pdata->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	ret = devm_rtc_register_device(pdata->rtc);
+	if (!ret)
+		return 0;
+
+	return ret;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id rtc_mv_of_match_table[] = {
+	{ .compatible = "marvell,orion-rtc", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, rtc_mv_of_match_table);
+#endif
+
+#ifdef CONFIG_PM_SLEEP
+static int mv_rtc_suspend(struct device *dev)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev) && pdata->irq >= 0)
+		enable_irq_wake(pdata->irq);
+	return 0;
+}
+
+static int mv_rtc_resume(struct device *dev)
+{
+	struct rtc_plat_data *pdata = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev) && pdata->irq >= 0)
+		disable_irq_wake(pdata->irq);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(mv_rtc_pm_ops, mv_rtc_suspend, mv_rtc_resume);
+
+static struct platform_driver mv_rtc_driver = {
+	.driver		= {
+		.name	= "rtc-mv",
+		.of_match_table = of_match_ptr(rtc_mv_of_match_table),
+		.pm	= &mv_rtc_pm_ops,
+	},
+};
+
+module_platform_driver_probe(mv_rtc_driver, mv_rtc_probe);
+
+MODULE_AUTHOR("Saeed Bishara <saeed@marvell.com>");
+MODULE_DESCRIPTION("Marvell RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rtc-mv");