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, 217 insertions, 0 deletions

diff --git a/drivers/mfd/max77843.c b/drivers/mfd/max77843.c
new file mode 100644
index 000000000..2a48577b1
--- /dev/null
+++ b/drivers/mfd/max77843.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// MFD core driver for the Maxim MAX77843
+//
+// Copyright (C) 2015 Samsung Electronics
+// Author: Jaewon Kim <jaewon02.kim@samsung.com>
+// Author: Beomho Seo <beomho.seo@samsung.com>
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/max77693-common.h>
+#include <linux/mfd/max77843-private.h>
+#include <linux/platform_device.h>
+
+static const struct mfd_cell max77843_devs[] = {
+	{
+		.name = "max77843-muic",
+		.of_compatible = "maxim,max77843-muic",
+	}, {
+		.name = "max77843-regulator",
+		.of_compatible = "maxim,max77843-regulator",
+	}, {
+		.name = "max77843-charger",
+		.of_compatible = "maxim,max77843-charger"
+	}, {
+		.name = "max77843-fuelgauge",
+		.of_compatible = "maxim,max77843-fuelgauge",
+	}, {
+		.name = "max77843-haptic",
+		.of_compatible = "maxim,max77843-haptic",
+	},
+};
+
+static const struct regmap_config max77843_charger_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+	.max_register	= MAX77843_CHG_REG_END,
+};
+
+static const struct regmap_config max77843_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+	.max_register	= MAX77843_SYS_REG_END,
+};
+
+static const struct regmap_irq max77843_irqs[] = {
+	/* TOPSYS interrupts */
+	{ .reg_offset = 0, .mask = MAX77843_SYS_IRQ_SYSUVLO_INT, },
+	{ .reg_offset = 0, .mask = MAX77843_SYS_IRQ_SYSOVLO_INT, },
+	{ .reg_offset = 0, .mask = MAX77843_SYS_IRQ_TSHDN_INT, },
+	{ .reg_offset = 0, .mask = MAX77843_SYS_IRQ_TM_INT, },
+};
+
+static const struct regmap_irq_chip max77843_irq_chip = {
+	.name		= "max77843",
+	.status_base	= MAX77843_SYS_REG_SYSINTSRC,
+	.mask_base	= MAX77843_SYS_REG_SYSINTMASK,
+	.num_regs	= 1,
+	.irqs		= max77843_irqs,
+	.num_irqs	= ARRAY_SIZE(max77843_irqs),
+};
+
+/* Charger and Charger regulator use same regmap. */
+static int max77843_chg_init(struct max77693_dev *max77843)
+{
+	int ret;
+
+	max77843->i2c_chg = i2c_new_dummy_device(max77843->i2c->adapter, I2C_ADDR_CHG);
+	if (IS_ERR(max77843->i2c_chg)) {
+		dev_err(&max77843->i2c->dev,
+				"Cannot allocate I2C device for Charger\n");
+		return PTR_ERR(max77843->i2c_chg);
+	}
+	i2c_set_clientdata(max77843->i2c_chg, max77843);
+
+	max77843->regmap_chg = devm_regmap_init_i2c(max77843->i2c_chg,
+			&max77843_charger_regmap_config);
+	if (IS_ERR(max77843->regmap_chg)) {
+		ret = PTR_ERR(max77843->regmap_chg);
+		goto err_chg_i2c;
+	}
+
+	return 0;
+
+err_chg_i2c:
+	i2c_unregister_device(max77843->i2c_chg);
+
+	return ret;
+}
+
+static int max77843_probe(struct i2c_client *i2c)
+{
+	const struct i2c_device_id *id = i2c_client_get_device_id(i2c);
+	struct max77693_dev *max77843;
+	unsigned int reg_data;
+	int ret;
+
+	max77843 = devm_kzalloc(&i2c->dev, sizeof(*max77843), GFP_KERNEL);
+	if (!max77843)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, max77843);
+	max77843->dev = &i2c->dev;
+	max77843->i2c = i2c;
+	max77843->irq = i2c->irq;
+	max77843->type = id->driver_data;
+
+	max77843->regmap = devm_regmap_init_i2c(i2c,
+			&max77843_regmap_config);
+	if (IS_ERR(max77843->regmap)) {
+		dev_err(&i2c->dev, "Failed to allocate topsys register map\n");
+		return PTR_ERR(max77843->regmap);
+	}
+
+	ret = regmap_add_irq_chip(max77843->regmap, max77843->irq,
+			IRQF_TRIGGER_LOW | IRQF_ONESHOT | IRQF_SHARED,
+			0, &max77843_irq_chip, &max77843->irq_data_topsys);
+	if (ret) {
+		dev_err(&i2c->dev, "Failed to add TOPSYS IRQ chip\n");
+		return ret;
+	}
+
+	ret = regmap_read(max77843->regmap,
+			MAX77843_SYS_REG_PMICID, &reg_data);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Failed to read PMIC ID\n");
+		goto err_pmic_id;
+	}
+	dev_info(&i2c->dev, "device ID: 0x%x\n", reg_data);
+
+	ret = max77843_chg_init(max77843);
+	if (ret) {
+		dev_err(&i2c->dev, "Failed to init Charger\n");
+		goto err_pmic_id;
+	}
+
+	ret = regmap_update_bits(max77843->regmap,
+				 MAX77843_SYS_REG_INTSRCMASK,
+				 MAX77843_INTSRC_MASK_MASK,
+				 (unsigned int)~MAX77843_INTSRC_MASK_MASK);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Failed to unmask interrupt source\n");
+		goto err_pmic_id;
+	}
+
+	ret = mfd_add_devices(max77843->dev, -1, max77843_devs,
+			      ARRAY_SIZE(max77843_devs), NULL, 0, NULL);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Failed to add mfd device\n");
+		goto err_pmic_id;
+	}
+
+	device_init_wakeup(max77843->dev, true);
+
+	return 0;
+
+err_pmic_id:
+	regmap_del_irq_chip(max77843->irq, max77843->irq_data_topsys);
+
+	return ret;
+}
+
+static const struct of_device_id max77843_dt_match[] = {
+	{ .compatible = "maxim,max77843", },
+	{ },
+};
+
+static const struct i2c_device_id max77843_id[] = {
+	{ "max77843", TYPE_MAX77843, },
+	{ },
+};
+
+static int __maybe_unused max77843_suspend(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct max77693_dev *max77843 = i2c_get_clientdata(i2c);
+
+	disable_irq(max77843->irq);
+	if (device_may_wakeup(dev))
+		enable_irq_wake(max77843->irq);
+
+	return 0;
+}
+
+static int __maybe_unused max77843_resume(struct device *dev)
+{
+	struct i2c_client *i2c = to_i2c_client(dev);
+	struct max77693_dev *max77843 = i2c_get_clientdata(i2c);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(max77843->irq);
+	enable_irq(max77843->irq);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(max77843_pm, max77843_suspend, max77843_resume);
+
+static struct i2c_driver max77843_i2c_driver = {
+	.driver	= {
+		.name = "max77843",
+		.pm = &max77843_pm,
+		.of_match_table = max77843_dt_match,
+		.suppress_bind_attrs = true,
+	},
+	.probe = max77843_probe,
+	.id_table = max77843_id,
+};
+
+static int __init max77843_i2c_init(void)
+{
+	return i2c_add_driver(&max77843_i2c_driver);
+}
+subsys_initcall(max77843_i2c_init);