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, 349 insertions, 0 deletions

diff --git a/drivers/mfd/max8998.c b/drivers/mfd/max8998.c
new file mode 100644
index 000000000..eb13bbaed
--- /dev/null
+++ b/drivers/mfd/max8998.c
@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// max8998.c - mfd core driver for the Maxim 8998
+//
+//  Copyright (C) 2009-2010 Samsung Electronics
+//  Kyungmin Park <kyungmin.park@samsung.com>
+//  Marek Szyprowski <m.szyprowski@samsung.com>
+
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/pm_runtime.h>
+#include <linux/mutex.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/max8998.h>
+#include <linux/mfd/max8998-private.h>
+
+#define RTC_I2C_ADDR		(0x0c >> 1)
+
+static const struct mfd_cell max8998_devs[] = {
+	{
+		.name = "max8998-pmic",
+	}, {
+		.name = "max8998-rtc",
+	}, {
+		.name = "max8998-battery",
+	},
+};
+
+static const struct mfd_cell lp3974_devs[] = {
+	{
+		.name = "lp3974-pmic",
+	}, {
+		.name = "lp3974-rtc",
+	},
+};
+
+int max8998_read_reg(struct i2c_client *i2c, u8 reg, u8 *dest)
+{
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&max8998->iolock);
+	ret = i2c_smbus_read_byte_data(i2c, reg);
+	mutex_unlock(&max8998->iolock);
+	if (ret < 0)
+		return ret;
+
+	ret &= 0xff;
+	*dest = ret;
+	return 0;
+}
+EXPORT_SYMBOL(max8998_read_reg);
+
+int max8998_bulk_read(struct i2c_client *i2c, u8 reg, int count, u8 *buf)
+{
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&max8998->iolock);
+	ret = i2c_smbus_read_i2c_block_data(i2c, reg, count, buf);
+	mutex_unlock(&max8998->iolock);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(max8998_bulk_read);
+
+int max8998_write_reg(struct i2c_client *i2c, u8 reg, u8 value)
+{
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&max8998->iolock);
+	ret = i2c_smbus_write_byte_data(i2c, reg, value);
+	mutex_unlock(&max8998->iolock);
+	return ret;
+}
+EXPORT_SYMBOL(max8998_write_reg);
+
+int max8998_bulk_write(struct i2c_client *i2c, u8 reg, int count, u8 *buf)
+{
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&max8998->iolock);
+	ret = i2c_smbus_write_i2c_block_data(i2c, reg, count, buf);
+	mutex_unlock(&max8998->iolock);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(max8998_bulk_write);
+
+int max8998_update_reg(struct i2c_client *i2c, u8 reg, u8 val, u8 mask)
+{
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&max8998->iolock);
+	ret = i2c_smbus_read_byte_data(i2c, reg);
+	if (ret >= 0) {
+		u8 old_val = ret & 0xff;
+		u8 new_val = (val & mask) | (old_val & (~mask));
+		ret = i2c_smbus_write_byte_data(i2c, reg, new_val);
+	}
+	mutex_unlock(&max8998->iolock);
+	return ret;
+}
+EXPORT_SYMBOL(max8998_update_reg);
+
+#ifdef CONFIG_OF
+static const struct of_device_id max8998_dt_match[] = {
+	{ .compatible = "maxim,max8998", .data = (void *)TYPE_MAX8998 },
+	{ .compatible = "national,lp3974", .data = (void *)TYPE_LP3974 },
+	{ .compatible = "ti,lp3974", .data = (void *)TYPE_LP3974 },
+	{},
+};
+#endif
+
+/*
+ * Only the common platform data elements for max8998 are parsed here from the
+ * device tree. Other sub-modules of max8998 such as pmic, rtc and others have
+ * to parse their own platform data elements from device tree.
+ *
+ * The max8998 platform data structure is instantiated here and the drivers for
+ * the sub-modules need not instantiate another instance while parsing their
+ * platform data.
+ */
+static struct max8998_platform_data *max8998_i2c_parse_dt_pdata(
+							struct device *dev)
+{
+	struct max8998_platform_data *pd;
+
+	pd = devm_kzalloc(dev, sizeof(*pd), GFP_KERNEL);
+	if (!pd)
+		return ERR_PTR(-ENOMEM);
+
+	pd->ono = irq_of_parse_and_map(dev->of_node, 1);
+
+	/*
+	 * ToDo: the 'wakeup' member in the platform data is more of a linux
+	 * specfic information. Hence, there is no binding for that yet and
+	 * not parsed here.
+	 */
+	return pd;
+}
+
+static int max8998_i2c_probe(struct i2c_client *i2c)
+{
+	struct max8998_platform_data *pdata = dev_get_platdata(&i2c->dev);
+	struct max8998_dev *max8998;
+	int ret = 0;
+
+	max8998 = devm_kzalloc(&i2c->dev, sizeof(struct max8998_dev),
+				GFP_KERNEL);
+	if (max8998 == NULL)
+		return -ENOMEM;
+
+	if (IS_ENABLED(CONFIG_OF) && i2c->dev.of_node) {
+		pdata = max8998_i2c_parse_dt_pdata(&i2c->dev);
+		if (IS_ERR(pdata))
+			return PTR_ERR(pdata);
+	}
+
+	i2c_set_clientdata(i2c, max8998);
+	max8998->dev = &i2c->dev;
+	max8998->i2c = i2c;
+	max8998->irq = i2c->irq;
+	max8998->type = (uintptr_t)i2c_get_match_data(i2c);
+	max8998->pdata = pdata;
+	if (pdata) {
+		max8998->ono = pdata->ono;
+		max8998->irq_base = pdata->irq_base;
+		max8998->wakeup = pdata->wakeup;
+	}
+	mutex_init(&max8998->iolock);
+
+	max8998->rtc = i2c_new_dummy_device(i2c->adapter, RTC_I2C_ADDR);
+	if (IS_ERR(max8998->rtc)) {
+		dev_err(&i2c->dev, "Failed to allocate I2C device for RTC\n");
+		return PTR_ERR(max8998->rtc);
+	}
+	i2c_set_clientdata(max8998->rtc, max8998);
+
+	max8998_irq_init(max8998);
+
+	pm_runtime_set_active(max8998->dev);
+
+	switch (max8998->type) {
+	case TYPE_LP3974:
+		ret = mfd_add_devices(max8998->dev, -1,
+				      lp3974_devs, ARRAY_SIZE(lp3974_devs),
+				      NULL, 0, NULL);
+		break;
+	case TYPE_MAX8998:
+		ret = mfd_add_devices(max8998->dev, -1,
+				      max8998_devs, ARRAY_SIZE(max8998_devs),
+				      NULL, 0, NULL);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret < 0)
+		goto err;
+
+	device_init_wakeup(max8998->dev, max8998->wakeup);
+
+	return ret;
+
+err:
+	mfd_remove_devices(max8998->dev);
+	max8998_irq_exit(max8998);
+	i2c_unregister_device(max8998->rtc);
+	return ret;
+}
+
+static const struct i2c_device_id max8998_i2c_id[] = {
+	{ "max8998", TYPE_MAX8998 },
+	{ "lp3974", TYPE_LP3974},
+	{ }
+};
+
+static int max8998_suspend(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(max8998->irq);
+	return 0;
+}
+
+static int max8998_resume(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct max8998_dev *max8998 = i2c_get_clientdata(i2c);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(max8998->irq);
+	/*
+	 * In LP3974, if IRQ registers are not "read & clear"
+	 * when it's set during sleep, the interrupt becomes
+	 * disabled.
+	 */
+	return max8998_irq_resume(i2c_get_clientdata(i2c));
+}
+
+struct max8998_reg_dump {
+	u8	addr;
+	u8	val;
+};
+#define SAVE_ITEM(x)	{ .addr = (x), .val = 0x0, }
+static struct max8998_reg_dump max8998_dump[] = {
+	SAVE_ITEM(MAX8998_REG_IRQM1),
+	SAVE_ITEM(MAX8998_REG_IRQM2),
+	SAVE_ITEM(MAX8998_REG_IRQM3),
+	SAVE_ITEM(MAX8998_REG_IRQM4),
+	SAVE_ITEM(MAX8998_REG_STATUSM1),
+	SAVE_ITEM(MAX8998_REG_STATUSM2),
+	SAVE_ITEM(MAX8998_REG_CHGR1),
+	SAVE_ITEM(MAX8998_REG_CHGR2),
+	SAVE_ITEM(MAX8998_REG_LDO_ACTIVE_DISCHARGE1),
+	SAVE_ITEM(MAX8998_REG_LDO_ACTIVE_DISCHARGE1),
+	SAVE_ITEM(MAX8998_REG_BUCK_ACTIVE_DISCHARGE3),
+	SAVE_ITEM(MAX8998_REG_ONOFF1),
+	SAVE_ITEM(MAX8998_REG_ONOFF2),
+	SAVE_ITEM(MAX8998_REG_ONOFF3),
+	SAVE_ITEM(MAX8998_REG_ONOFF4),
+	SAVE_ITEM(MAX8998_REG_BUCK1_VOLTAGE1),
+	SAVE_ITEM(MAX8998_REG_BUCK1_VOLTAGE2),
+	SAVE_ITEM(MAX8998_REG_BUCK1_VOLTAGE3),
+	SAVE_ITEM(MAX8998_REG_BUCK1_VOLTAGE4),
+	SAVE_ITEM(MAX8998_REG_BUCK2_VOLTAGE1),
+	SAVE_ITEM(MAX8998_REG_BUCK2_VOLTAGE2),
+	SAVE_ITEM(MAX8998_REG_LDO2_LDO3),
+	SAVE_ITEM(MAX8998_REG_LDO4),
+	SAVE_ITEM(MAX8998_REG_LDO5),
+	SAVE_ITEM(MAX8998_REG_LDO6),
+	SAVE_ITEM(MAX8998_REG_LDO7),
+	SAVE_ITEM(MAX8998_REG_LDO8_LDO9),
+	SAVE_ITEM(MAX8998_REG_LDO10_LDO11),
+	SAVE_ITEM(MAX8998_REG_LDO12),
+	SAVE_ITEM(MAX8998_REG_LDO13),
+	SAVE_ITEM(MAX8998_REG_LDO14),
+	SAVE_ITEM(MAX8998_REG_LDO15),
+	SAVE_ITEM(MAX8998_REG_LDO16),
+	SAVE_ITEM(MAX8998_REG_LDO17),
+	SAVE_ITEM(MAX8998_REG_BKCHR),
+	SAVE_ITEM(MAX8998_REG_LBCNFG1),
+	SAVE_ITEM(MAX8998_REG_LBCNFG2),
+};
+/* Save registers before hibernation */
+static int max8998_freeze(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(max8998_dump); i++)
+		max8998_read_reg(i2c, max8998_dump[i].addr,
+				&max8998_dump[i].val);
+
+	return 0;
+}
+
+/* Restore registers after hibernation */
+static int max8998_restore(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(max8998_dump); i++)
+		max8998_write_reg(i2c, max8998_dump[i].addr,
+				max8998_dump[i].val);
+
+	return 0;
+}
+
+static const struct dev_pm_ops max8998_pm = {
+	.suspend = max8998_suspend,
+	.resume = max8998_resume,
+	.freeze = max8998_freeze,
+	.restore = max8998_restore,
+};
+
+static struct i2c_driver max8998_i2c_driver = {
+	.driver = {
+		   .name = "max8998",
+		   .pm = &max8998_pm,
+		   .suppress_bind_attrs = true,
+		   .of_match_table = of_match_ptr(max8998_dt_match),
+	},
+	.probe = max8998_i2c_probe,
+	.id_table = max8998_i2c_id,
+};
+
+static int __init max8998_i2c_init(void)
+{
+	return i2c_add_driver(&max8998_i2c_driver);
+}
+/* init early so consumer devices can complete system boot */
+subsys_initcall(max8998_i2c_init);