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, 133 insertions, 0 deletions

diff --git a/drivers/mfd/rt5033.c b/drivers/mfd/rt5033.c
new file mode 100644
index 000000000..072fd4447
--- /dev/null
+++ b/drivers/mfd/rt5033.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MFD core driver for the Richtek RT5033.
+ *
+ * RT5033 comprises multiple sub-devices switcing charger, fuel gauge,
+ * flash LED, current source, LDO and BUCK regulators.
+ *
+ * Copyright (C) 2014 Samsung Electronics, Co., Ltd.
+ * Author: Beomho Seo <beomho.seo@samsung.com>
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/rt5033.h>
+#include <linux/mfd/rt5033-private.h>
+
+static const struct regmap_irq rt5033_irqs[] = {
+	{ .mask = RT5033_PMIC_IRQ_BUCKOCP, },
+	{ .mask = RT5033_PMIC_IRQ_BUCKLV, },
+	{ .mask = RT5033_PMIC_IRQ_SAFELDOLV, },
+	{ .mask = RT5033_PMIC_IRQ_LDOLV, },
+	{ .mask = RT5033_PMIC_IRQ_OT, },
+	{ .mask = RT5033_PMIC_IRQ_VDDA_UV, },
+};
+
+static const struct regmap_irq_chip rt5033_irq_chip = {
+	.name		= "rt5033",
+	.status_base	= RT5033_REG_PMIC_IRQ_STAT,
+	.unmask_base	= RT5033_REG_PMIC_IRQ_CTRL,
+	.num_regs	= 1,
+	.irqs		= rt5033_irqs,
+	.num_irqs	= ARRAY_SIZE(rt5033_irqs),
+};
+
+static const struct mfd_cell rt5033_devs[] = {
+	{ .name = "rt5033-regulator", },
+	{
+		.name = "rt5033-charger",
+		.of_compatible = "richtek,rt5033-charger",
+	}, {
+		.name = "rt5033-led",
+		.of_compatible = "richtek,rt5033-led",
+	},
+};
+
+static const struct regmap_config rt5033_regmap_config = {
+	.reg_bits	= 8,
+	.val_bits	= 8,
+	.max_register	= RT5033_REG_END,
+};
+
+static int rt5033_i2c_probe(struct i2c_client *i2c)
+{
+	struct rt5033_dev *rt5033;
+	unsigned int dev_id, chip_rev;
+	int ret;
+
+	rt5033 = devm_kzalloc(&i2c->dev, sizeof(*rt5033), GFP_KERNEL);
+	if (!rt5033)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, rt5033);
+	rt5033->dev = &i2c->dev;
+	rt5033->irq = i2c->irq;
+	rt5033->wakeup = true;
+
+	rt5033->regmap = devm_regmap_init_i2c(i2c, &rt5033_regmap_config);
+	if (IS_ERR(rt5033->regmap)) {
+		dev_err(&i2c->dev, "Failed to allocate register map.\n");
+		return PTR_ERR(rt5033->regmap);
+	}
+
+	ret = regmap_read(rt5033->regmap, RT5033_REG_DEVICE_ID, &dev_id);
+	if (ret) {
+		dev_err(&i2c->dev, "Device not found\n");
+		return -ENODEV;
+	}
+	chip_rev = dev_id & RT5033_CHIP_REV_MASK;
+	dev_info(&i2c->dev, "Device found (rev. %d)\n", chip_rev);
+
+	ret = devm_regmap_add_irq_chip(rt5033->dev, rt5033->regmap,
+			rt5033->irq, IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+			0, &rt5033_irq_chip, &rt5033->irq_data);
+	if (ret) {
+		dev_err(&i2c->dev, "Failed to request IRQ %d: %d\n",
+							rt5033->irq, ret);
+		return ret;
+	}
+
+	ret = devm_mfd_add_devices(rt5033->dev, -1, rt5033_devs,
+				   ARRAY_SIZE(rt5033_devs), NULL, 0,
+				   regmap_irq_get_domain(rt5033->irq_data));
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Failed to add RT5033 child devices.\n");
+		return ret;
+	}
+
+	if (rt5033->wakeup) {
+		ret = devm_device_init_wakeup(rt5033->dev);
+		if (ret)
+			return dev_err_probe(rt5033->dev, ret, "Failed to init wakeup\n");
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id rt5033_i2c_id[] = {
+	{ "rt5033", },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, rt5033_i2c_id);
+
+static const struct of_device_id rt5033_dt_match[] = {
+	{ .compatible = "richtek,rt5033", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, rt5033_dt_match);
+
+static struct i2c_driver rt5033_driver = {
+	.driver = {
+		.name = "rt5033",
+		.of_match_table = rt5033_dt_match,
+	},
+	.probe = rt5033_i2c_probe,
+	.id_table = rt5033_i2c_id,
+};
+module_i2c_driver(rt5033_driver);
+
+MODULE_DESCRIPTION("Richtek RT5033 multi-function core driver");
+MODULE_AUTHOR("Beomho Seo <beomho.seo@samsung.com>");
+MODULE_LICENSE("GPL");