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, 119 insertions, 0 deletions

diff --git a/drivers/input/misc/rt5120-pwrkey.c b/drivers/input/misc/rt5120-pwrkey.c
new file mode 100644
index 000000000..2262f5057
--- /dev/null
+++ b/drivers/input/misc/rt5120-pwrkey.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Richtek Technology Corp.
+ * Author: ChiYuan Huang <cy_huang@richtek.com>
+ */
+
+#include <linux/bits.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define RT5120_REG_INTSTAT	0x1E
+#define RT5120_PWRKEYSTAT_MASK	BIT(7)
+
+struct rt5120_priv {
+	struct regmap *regmap;
+	struct input_dev *input;
+};
+
+static irqreturn_t rt5120_pwrkey_handler(int irq, void *devid)
+{
+	struct rt5120_priv *priv = devid;
+	unsigned int stat;
+	int error;
+
+	error = regmap_read(priv->regmap, RT5120_REG_INTSTAT, &stat);
+	if (error)
+		return IRQ_NONE;
+
+	input_report_key(priv->input, KEY_POWER,
+			 !(stat & RT5120_PWRKEYSTAT_MASK));
+	input_sync(priv->input);
+
+	return IRQ_HANDLED;
+}
+
+static int rt5120_pwrkey_probe(struct platform_device *pdev)
+{
+	struct rt5120_priv *priv;
+	struct device *dev = &pdev->dev;
+	int press_irq, release_irq;
+	int error;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->regmap = dev_get_regmap(dev->parent, NULL);
+	if (!priv->regmap) {
+		dev_err(dev, "Failed to init regmap\n");
+		return -ENODEV;
+	}
+
+	press_irq = platform_get_irq_byname(pdev, "pwrkey-press");
+	if (press_irq < 0)
+		return press_irq;
+
+	release_irq = platform_get_irq_byname(pdev, "pwrkey-release");
+	if (release_irq < 0)
+		return release_irq;
+
+	/* Make input device be device resource managed */
+	priv->input = devm_input_allocate_device(dev);
+	if (!priv->input)
+		return -ENOMEM;
+
+	priv->input->name = "rt5120_pwrkey";
+	priv->input->phys = "rt5120_pwrkey/input0";
+	priv->input->id.bustype = BUS_I2C;
+	input_set_capability(priv->input, EV_KEY, KEY_POWER);
+
+	error = input_register_device(priv->input);
+	if (error) {
+		dev_err(dev, "Failed to register input device: %d\n", error);
+		return error;
+	}
+
+	error = devm_request_threaded_irq(dev, press_irq,
+					  NULL, rt5120_pwrkey_handler,
+					  0, "pwrkey-press", priv);
+	if (error) {
+		dev_err(dev,
+			"Failed to register pwrkey press irq: %d\n", error);
+		return error;
+	}
+
+	error = devm_request_threaded_irq(dev, release_irq,
+					  NULL, rt5120_pwrkey_handler,
+					  0, "pwrkey-release", priv);
+	if (error) {
+		dev_err(dev,
+			"Failed to register pwrkey release irq: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id r5120_pwrkey_match_table[] = {
+	{ .compatible = "richtek,rt5120-pwrkey" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, r5120_pwrkey_match_table);
+
+static struct platform_driver rt5120_pwrkey_driver = {
+	.driver = {
+		.name = "rt5120-pwrkey",
+		.of_match_table = r5120_pwrkey_match_table,
+	},
+	.probe = rt5120_pwrkey_probe,
+};
+module_platform_driver(rt5120_pwrkey_driver);
+
+MODULE_AUTHOR("ChiYuan Huang <cy_huang@richtek.com>");
+MODULE_DESCRIPTION("Richtek RT5120 power key driver");
+MODULE_LICENSE("GPL");