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, 278 insertions, 0 deletions

diff --git a/drivers/mfd/max77686.c b/drivers/mfd/max77686.c
new file mode 100644
index 000000000..0118a444a
--- /dev/null
+++ b/drivers/mfd/max77686.c
@@ -0,0 +1,278 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// max77686.c - mfd core driver for the Maxim 77686/802
+//
+// Copyright (C) 2012 Samsung Electronics
+// Chiwoong Byun <woong.byun@samsung.com>
+// Jonghwa Lee <jonghwa3.lee@samsung.com>
+//
+//This driver is based on max8997.c
+
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
+#include <linux/pm_runtime.h>
+#include <linux/module.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/max77686.h>
+#include <linux/mfd/max77686-private.h>
+#include <linux/err.h>
+#include <linux/of.h>
+
+static const struct mfd_cell max77686_devs[] = {
+	{ .name = "max77686-pmic", },
+	{ .name = "max77686-rtc", },
+	{ .name = "max77686-clk", },
+};
+
+static const struct mfd_cell max77802_devs[] = {
+	{ .name = "max77802-pmic", },
+	{ .name = "max77802-clk", },
+	{ .name = "max77802-rtc", },
+};
+
+static bool max77802_pmic_is_accessible_reg(struct device *dev,
+					    unsigned int reg)
+{
+	return reg < MAX77802_REG_PMIC_END;
+}
+
+static bool max77802_rtc_is_accessible_reg(struct device *dev,
+					   unsigned int reg)
+{
+	return (reg >= MAX77802_RTC_INT && reg < MAX77802_RTC_END);
+}
+
+static bool max77802_is_accessible_reg(struct device *dev, unsigned int reg)
+{
+	return (max77802_pmic_is_accessible_reg(dev, reg) ||
+		max77802_rtc_is_accessible_reg(dev, reg));
+}
+
+static bool max77802_pmic_is_precious_reg(struct device *dev, unsigned int reg)
+{
+	return (reg == MAX77802_REG_INTSRC || reg == MAX77802_REG_INT1 ||
+		reg == MAX77802_REG_INT2);
+}
+
+static bool max77802_rtc_is_precious_reg(struct device *dev, unsigned int reg)
+{
+	return (reg == MAX77802_RTC_INT ||
+		reg == MAX77802_RTC_UPDATE0 ||
+		reg == MAX77802_RTC_UPDATE1);
+}
+
+static bool max77802_is_precious_reg(struct device *dev, unsigned int reg)
+{
+	return (max77802_pmic_is_precious_reg(dev, reg) ||
+		max77802_rtc_is_precious_reg(dev, reg));
+}
+
+static bool max77802_pmic_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return (max77802_is_precious_reg(dev, reg) ||
+		reg == MAX77802_REG_STATUS1 || reg == MAX77802_REG_STATUS2 ||
+		reg == MAX77802_REG_PWRON);
+}
+
+static bool max77802_rtc_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return (max77802_rtc_is_precious_reg(dev, reg) ||
+		reg == MAX77802_RTC_SEC ||
+		reg == MAX77802_RTC_MIN ||
+		reg == MAX77802_RTC_HOUR ||
+		reg == MAX77802_RTC_WEEKDAY ||
+		reg == MAX77802_RTC_MONTH ||
+		reg == MAX77802_RTC_YEAR ||
+		reg == MAX77802_RTC_MONTHDAY);
+}
+
+static bool max77802_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return (max77802_pmic_is_volatile_reg(dev, reg) ||
+		max77802_rtc_is_volatile_reg(dev, reg));
+}
+
+static const struct regmap_config max77686_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static const struct regmap_config max77802_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.writeable_reg = max77802_is_accessible_reg,
+	.readable_reg = max77802_is_accessible_reg,
+	.precious_reg = max77802_is_precious_reg,
+	.volatile_reg = max77802_is_volatile_reg,
+	.name = "max77802-pmic",
+	.cache_type = REGCACHE_MAPLE,
+};
+
+static const struct regmap_irq max77686_irqs[] = {
+	/* INT1 interrupts */
+	{ .reg_offset = 0, .mask = MAX77686_INT1_PWRONF_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_PWRONR_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_JIGONBF_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_JIGONBR_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_ACOKBF_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_ACOKBR_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_ONKEY1S_MSK, },
+	{ .reg_offset = 0, .mask = MAX77686_INT1_MRSTB_MSK, },
+	/* INT2 interrupts */
+	{ .reg_offset = 1, .mask = MAX77686_INT2_140C_MSK, },
+	{ .reg_offset = 1, .mask = MAX77686_INT2_120C_MSK, },
+};
+
+static const struct regmap_irq_chip max77686_irq_chip = {
+	.name			= "max77686-pmic",
+	.status_base		= MAX77686_REG_INT1,
+	.mask_base		= MAX77686_REG_INT1MSK,
+	.num_regs		= 2,
+	.irqs			= max77686_irqs,
+	.num_irqs		= ARRAY_SIZE(max77686_irqs),
+};
+
+static const struct regmap_irq_chip max77802_irq_chip = {
+	.name			= "max77802-pmic",
+	.status_base		= MAX77802_REG_INT1,
+	.mask_base		= MAX77802_REG_INT1MSK,
+	.num_regs		= 2,
+	.irqs			= max77686_irqs, /* same masks as 77686 */
+	.num_irqs		= ARRAY_SIZE(max77686_irqs),
+};
+
+static const struct of_device_id max77686_pmic_dt_match[] = {
+	{
+		.compatible = "maxim,max77686",
+		.data = (void *)TYPE_MAX77686,
+	},
+	{
+		.compatible = "maxim,max77802",
+		.data = (void *)TYPE_MAX77802,
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, max77686_pmic_dt_match);
+
+static int max77686_i2c_probe(struct i2c_client *i2c)
+{
+	struct max77686_dev *max77686 = NULL;
+	unsigned int data;
+	int ret = 0;
+	const struct regmap_config *config;
+	const struct regmap_irq_chip *irq_chip;
+	const struct mfd_cell *cells;
+	int n_devs;
+
+	max77686 = devm_kzalloc(&i2c->dev,
+				sizeof(struct max77686_dev), GFP_KERNEL);
+	if (!max77686)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, max77686);
+	max77686->type = (unsigned long)of_device_get_match_data(&i2c->dev);
+	max77686->dev = &i2c->dev;
+	max77686->i2c = i2c;
+
+	max77686->irq = i2c->irq;
+
+	if (max77686->type == TYPE_MAX77686) {
+		config = &max77686_regmap_config;
+		irq_chip = &max77686_irq_chip;
+		cells =  max77686_devs;
+		n_devs = ARRAY_SIZE(max77686_devs);
+	} else {
+		config = &max77802_regmap_config;
+		irq_chip = &max77802_irq_chip;
+		cells =  max77802_devs;
+		n_devs = ARRAY_SIZE(max77802_devs);
+	}
+
+	max77686->regmap = devm_regmap_init_i2c(i2c, config);
+	if (IS_ERR(max77686->regmap)) {
+		ret = PTR_ERR(max77686->regmap);
+		dev_err(max77686->dev, "Failed to allocate register map: %d\n",
+				ret);
+		return ret;
+	}
+
+	ret = regmap_read(max77686->regmap, MAX77686_REG_DEVICE_ID, &data);
+	if (ret < 0) {
+		dev_err(max77686->dev,
+			"device not found on this channel (this is not an error)\n");
+		return -ENODEV;
+	}
+
+	ret = devm_regmap_add_irq_chip(&i2c->dev, max77686->regmap,
+				       max77686->irq,
+				       IRQF_ONESHOT | IRQF_SHARED, 0, irq_chip,
+				       &max77686->irq_data);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "failed to add PMIC irq chip: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_mfd_add_devices(max77686->dev, -1, cells, n_devs, NULL,
+				   0, NULL);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "failed to add MFD devices: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int max77686_suspend(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct max77686_dev *max77686 = i2c_get_clientdata(i2c);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(max77686->irq);
+
+	/*
+	 * IRQ must be disabled during suspend because if it happens
+	 * while suspended it will be handled before resuming I2C.
+	 *
+	 * When device is woken up from suspend (e.g. by RTC wake alarm),
+	 * an interrupt occurs before resuming I2C bus controller.
+	 * Interrupt handler tries to read registers but this read
+	 * will fail because I2C is still suspended.
+	 */
+	disable_irq(max77686->irq);
+
+	return 0;
+}
+
+static int max77686_resume(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct max77686_dev *max77686 = i2c_get_clientdata(i2c);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(max77686->irq);
+
+	enable_irq(max77686->irq);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(max77686_pm, max77686_suspend, max77686_resume);
+
+static struct i2c_driver max77686_i2c_driver = {
+	.driver = {
+		   .name = "max77686",
+		   .pm = pm_sleep_ptr(&max77686_pm),
+		   .of_match_table = max77686_pmic_dt_match,
+	},
+	.probe = max77686_i2c_probe,
+};
+
+module_i2c_driver(max77686_i2c_driver);
+
+MODULE_DESCRIPTION("MAXIM 77686/802 multi-function core driver");
+MODULE_AUTHOR("Chiwoong Byun <woong.byun@samsung.com>");
+MODULE_LICENSE("GPL");