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, 362 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-palmas.c b/drivers/rtc/rtc-palmas.c
new file mode 100644
index 000000000..aecada6bc
--- /dev/null
+++ b/drivers/rtc/rtc-palmas.c
@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * rtc-palmas.c -- Palmas Real Time Clock driver.
+
+ * RTC driver for TI Palma series devices like TPS65913,
+ * TPS65914 power management IC.
+ *
+ * Copyright (c) 2012, NVIDIA Corporation.
+ *
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ */
+
+#include <linux/bcd.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/palmas.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/rtc.h>
+#include <linux/types.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+
+struct palmas_rtc {
+	struct rtc_device	*rtc;
+	struct device		*dev;
+	unsigned int		irq;
+};
+
+/* Total number of RTC registers needed to set time*/
+#define PALMAS_NUM_TIME_REGS	(PALMAS_YEARS_REG - PALMAS_SECONDS_REG + 1)
+
+static int palmas_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned char rtc_data[PALMAS_NUM_TIME_REGS];
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	/* Copy RTC counting registers to static registers or latches */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+		PALMAS_RTC_CTRL_REG_GET_TIME, PALMAS_RTC_CTRL_REG_GET_TIME);
+	if (ret < 0) {
+		dev_err(dev, "RTC CTRL reg update failed, err: %d\n", ret);
+		return ret;
+	}
+
+	ret = palmas_bulk_read(palmas, PALMAS_RTC_BASE, PALMAS_SECONDS_REG,
+			rtc_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "RTC_SECONDS reg read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	tm->tm_sec = bcd2bin(rtc_data[0]);
+	tm->tm_min = bcd2bin(rtc_data[1]);
+	tm->tm_hour = bcd2bin(rtc_data[2]);
+	tm->tm_mday = bcd2bin(rtc_data[3]);
+	tm->tm_mon = bcd2bin(rtc_data[4]) - 1;
+	tm->tm_year = bcd2bin(rtc_data[5]) + 100;
+
+	return ret;
+}
+
+static int palmas_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned char rtc_data[PALMAS_NUM_TIME_REGS];
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	rtc_data[0] = bin2bcd(tm->tm_sec);
+	rtc_data[1] = bin2bcd(tm->tm_min);
+	rtc_data[2] = bin2bcd(tm->tm_hour);
+	rtc_data[3] = bin2bcd(tm->tm_mday);
+	rtc_data[4] = bin2bcd(tm->tm_mon + 1);
+	rtc_data[5] = bin2bcd(tm->tm_year - 100);
+
+	/* Stop RTC while updating the RTC time registers */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+		PALMAS_RTC_CTRL_REG_STOP_RTC, 0);
+	if (ret < 0) {
+		dev_err(dev, "RTC stop failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = palmas_bulk_write(palmas, PALMAS_RTC_BASE, PALMAS_SECONDS_REG,
+		rtc_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "RTC_SECONDS reg write failed, err = %d\n", ret);
+		return ret;
+	}
+
+	/* Start back RTC */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+		PALMAS_RTC_CTRL_REG_STOP_RTC, PALMAS_RTC_CTRL_REG_STOP_RTC);
+	if (ret < 0)
+		dev_err(dev, "RTC start failed, err = %d\n", ret);
+	return ret;
+}
+
+static int palmas_rtc_alarm_irq_enable(struct device *dev, unsigned enabled)
+{
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	u8 val;
+
+	val = enabled ? PALMAS_RTC_INTERRUPTS_REG_IT_ALARM : 0;
+	return palmas_write(palmas, PALMAS_RTC_BASE,
+		PALMAS_RTC_INTERRUPTS_REG, val);
+}
+
+static int palmas_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	unsigned char alarm_data[PALMAS_NUM_TIME_REGS];
+	u32 int_val;
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	ret = palmas_bulk_read(palmas, PALMAS_RTC_BASE,
+			PALMAS_ALARM_SECONDS_REG,
+			alarm_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "RTC_ALARM_SECONDS read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	alm->time.tm_sec = bcd2bin(alarm_data[0]);
+	alm->time.tm_min = bcd2bin(alarm_data[1]);
+	alm->time.tm_hour = bcd2bin(alarm_data[2]);
+	alm->time.tm_mday = bcd2bin(alarm_data[3]);
+	alm->time.tm_mon = bcd2bin(alarm_data[4]) - 1;
+	alm->time.tm_year = bcd2bin(alarm_data[5]) + 100;
+
+	ret = palmas_read(palmas, PALMAS_RTC_BASE, PALMAS_RTC_INTERRUPTS_REG,
+			&int_val);
+	if (ret < 0) {
+		dev_err(dev, "RTC_INTERRUPTS reg read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	if (int_val & PALMAS_RTC_INTERRUPTS_REG_IT_ALARM)
+		alm->enabled = 1;
+	return ret;
+}
+
+static int palmas_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	unsigned char alarm_data[PALMAS_NUM_TIME_REGS];
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	int ret;
+
+	ret = palmas_rtc_alarm_irq_enable(dev, 0);
+	if (ret < 0) {
+		dev_err(dev, "Disable RTC alarm failed\n");
+		return ret;
+	}
+
+	alarm_data[0] = bin2bcd(alm->time.tm_sec);
+	alarm_data[1] = bin2bcd(alm->time.tm_min);
+	alarm_data[2] = bin2bcd(alm->time.tm_hour);
+	alarm_data[3] = bin2bcd(alm->time.tm_mday);
+	alarm_data[4] = bin2bcd(alm->time.tm_mon + 1);
+	alarm_data[5] = bin2bcd(alm->time.tm_year - 100);
+
+	ret = palmas_bulk_write(palmas, PALMAS_RTC_BASE,
+		PALMAS_ALARM_SECONDS_REG, alarm_data, PALMAS_NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "ALARM_SECONDS_REG write failed, err = %d\n", ret);
+		return ret;
+	}
+
+	if (alm->enabled)
+		ret = palmas_rtc_alarm_irq_enable(dev, 1);
+	return ret;
+}
+
+static int palmas_clear_interrupts(struct device *dev)
+{
+	struct palmas *palmas = dev_get_drvdata(dev->parent);
+	unsigned int rtc_reg;
+	int ret;
+
+	ret = palmas_read(palmas, PALMAS_RTC_BASE, PALMAS_RTC_STATUS_REG,
+				&rtc_reg);
+	if (ret < 0) {
+		dev_err(dev, "RTC_STATUS read failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = palmas_write(palmas, PALMAS_RTC_BASE, PALMAS_RTC_STATUS_REG,
+			rtc_reg);
+	if (ret < 0) {
+		dev_err(dev, "RTC_STATUS write failed, err = %d\n", ret);
+		return ret;
+	}
+	return 0;
+}
+
+static irqreturn_t palmas_rtc_interrupt(int irq, void *context)
+{
+	struct palmas_rtc *palmas_rtc = context;
+	struct device *dev = palmas_rtc->dev;
+	int ret;
+
+	ret = palmas_clear_interrupts(dev);
+	if (ret < 0) {
+		dev_err(dev, "RTC interrupt clear failed, err = %d\n", ret);
+		return IRQ_NONE;
+	}
+
+	rtc_update_irq(palmas_rtc->rtc, 1, RTC_IRQF | RTC_AF);
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops palmas_rtc_ops = {
+	.read_time	= palmas_rtc_read_time,
+	.set_time	= palmas_rtc_set_time,
+	.read_alarm	= palmas_rtc_read_alarm,
+	.set_alarm	= palmas_rtc_set_alarm,
+	.alarm_irq_enable = palmas_rtc_alarm_irq_enable,
+};
+
+static int palmas_rtc_probe(struct platform_device *pdev)
+{
+	struct palmas *palmas = dev_get_drvdata(pdev->dev.parent);
+	struct palmas_rtc *palmas_rtc = NULL;
+	int ret;
+	bool enable_bb_charging = false;
+	bool high_bb_charging = false;
+
+	if (pdev->dev.of_node) {
+		enable_bb_charging = of_property_read_bool(pdev->dev.of_node,
+					"ti,backup-battery-chargeable");
+		high_bb_charging = of_property_read_bool(pdev->dev.of_node,
+					"ti,backup-battery-charge-high-current");
+	}
+
+	palmas_rtc = devm_kzalloc(&pdev->dev, sizeof(struct palmas_rtc),
+			GFP_KERNEL);
+	if (!palmas_rtc)
+		return -ENOMEM;
+
+	/* Clear pending interrupts */
+	ret = palmas_clear_interrupts(&pdev->dev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "clear RTC int failed, err = %d\n", ret);
+		return ret;
+	}
+
+	palmas_rtc->dev = &pdev->dev;
+	platform_set_drvdata(pdev, palmas_rtc);
+
+	if (enable_bb_charging) {
+		unsigned reg = PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG;
+
+		if (high_bb_charging)
+			reg = 0;
+
+		ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+			PALMAS_BACKUP_BATTERY_CTRL,
+			PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG, reg);
+		if (ret < 0) {
+			dev_err(&pdev->dev,
+				"BACKUP_BATTERY_CTRL update failed, %d\n", ret);
+			return ret;
+		}
+
+		ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
+			PALMAS_BACKUP_BATTERY_CTRL,
+			PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN,
+			PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN);
+		if (ret < 0) {
+			dev_err(&pdev->dev,
+				"BACKUP_BATTERY_CTRL update failed, %d\n", ret);
+			return ret;
+		}
+	}
+
+	/* Start RTC */
+	ret = palmas_update_bits(palmas, PALMAS_RTC_BASE, PALMAS_RTC_CTRL_REG,
+			PALMAS_RTC_CTRL_REG_STOP_RTC,
+			PALMAS_RTC_CTRL_REG_STOP_RTC);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "RTC_CTRL write failed, err = %d\n", ret);
+		return ret;
+	}
+
+	palmas_rtc->irq = platform_get_irq(pdev, 0);
+
+	device_init_wakeup(&pdev->dev, true);
+	palmas_rtc->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
+				&palmas_rtc_ops, THIS_MODULE);
+	if (IS_ERR(palmas_rtc->rtc)) {
+		ret = PTR_ERR(palmas_rtc->rtc);
+		dev_err(&pdev->dev, "RTC register failed, err = %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_request_threaded_irq(&pdev->dev, palmas_rtc->irq, NULL,
+			palmas_rtc_interrupt,
+			IRQF_TRIGGER_LOW | IRQF_ONESHOT,
+			dev_name(&pdev->dev), palmas_rtc);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "IRQ request failed, err = %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void palmas_rtc_remove(struct platform_device *pdev)
+{
+	palmas_rtc_alarm_irq_enable(&pdev->dev, 0);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int palmas_rtc_suspend(struct device *dev)
+{
+	struct palmas_rtc *palmas_rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(palmas_rtc->irq);
+	return 0;
+}
+
+static int palmas_rtc_resume(struct device *dev)
+{
+	struct palmas_rtc *palmas_rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(palmas_rtc->irq);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(palmas_rtc_pm_ops, palmas_rtc_suspend,
+			 palmas_rtc_resume);
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_palmas_rtc_match[] = {
+	{ .compatible = "ti,palmas-rtc"},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, of_palmas_rtc_match);
+#endif
+
+static struct platform_driver palmas_rtc_driver = {
+	.probe		= palmas_rtc_probe,
+	.remove		= palmas_rtc_remove,
+	.driver		= {
+		.name	= "palmas-rtc",
+		.pm	= &palmas_rtc_pm_ops,
+		.of_match_table = of_match_ptr(of_palmas_rtc_match),
+	},
+};
+
+module_platform_driver(palmas_rtc_driver);
+
+MODULE_ALIAS("platform:palmas_rtc");
+MODULE_DESCRIPTION("TI PALMAS series RTC driver");
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
+MODULE_LICENSE("GPL v2");