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, 160 insertions, 0 deletions

diff --git a/drivers/input/misc/tps65218-pwrbutton.c b/drivers/input/misc/tps65218-pwrbutton.c
new file mode 100644
index 000000000..fc450fce0
--- /dev/null
+++ b/drivers/input/misc/tps65218-pwrbutton.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Texas Instruments' TPS65217 and TPS65218 Power Button Input Driver
+ *
+ * Copyright (C) 2014 Texas Instruments Incorporated - http://www.ti.com/
+ * Author: Felipe Balbi <balbi@ti.com>
+ * Author: Marcin Niestroj <m.niestroj@grinn-global.com>
+ */
+
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/tps65217.h>
+#include <linux/mfd/tps65218.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+struct tps6521x_data {
+	unsigned int reg_status;
+	unsigned int pb_mask;
+	const char *name;
+};
+
+static const struct tps6521x_data tps65217_data = {
+	.reg_status = TPS65217_REG_STATUS,
+	.pb_mask = TPS65217_STATUS_PB,
+	.name = "tps65217_pwrbutton",
+};
+
+static const struct tps6521x_data tps65218_data = {
+	.reg_status = TPS65218_REG_STATUS,
+	.pb_mask = TPS65218_STATUS_PB_STATE,
+	.name = "tps65218_pwrbutton",
+};
+
+struct tps6521x_pwrbutton {
+	struct device *dev;
+	struct regmap *regmap;
+	struct input_dev *idev;
+	const struct tps6521x_data *data;
+	char phys[32];
+};
+
+static const struct of_device_id of_tps6521x_pb_match[] = {
+	{ .compatible = "ti,tps65217-pwrbutton", .data = &tps65217_data },
+	{ .compatible = "ti,tps65218-pwrbutton", .data = &tps65218_data },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, of_tps6521x_pb_match);
+
+static irqreturn_t tps6521x_pb_irq(int irq, void *_pwr)
+{
+	struct tps6521x_pwrbutton *pwr = _pwr;
+	const struct tps6521x_data *tps_data = pwr->data;
+	unsigned int reg;
+	int error;
+
+	error = regmap_read(pwr->regmap, tps_data->reg_status, &reg);
+	if (error) {
+		dev_err(pwr->dev, "can't read register: %d\n", error);
+		goto out;
+	}
+
+	if (reg & tps_data->pb_mask) {
+		input_report_key(pwr->idev, KEY_POWER, 1);
+		pm_wakeup_event(pwr->dev, 0);
+	} else {
+		input_report_key(pwr->idev, KEY_POWER, 0);
+	}
+
+	input_sync(pwr->idev);
+
+out:
+	return IRQ_HANDLED;
+}
+
+static int tps6521x_pb_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct tps6521x_pwrbutton *pwr;
+	struct input_dev *idev;
+	const struct of_device_id *match;
+	int error;
+	int irq;
+
+	match = of_match_node(of_tps6521x_pb_match, dev->of_node);
+	if (!match)
+		return -ENXIO;
+
+	pwr = devm_kzalloc(dev, sizeof(*pwr), GFP_KERNEL);
+	if (!pwr)
+		return -ENOMEM;
+
+	pwr->data = match->data;
+
+	idev = devm_input_allocate_device(dev);
+	if (!idev)
+		return -ENOMEM;
+
+	idev->name = pwr->data->name;
+	snprintf(pwr->phys, sizeof(pwr->phys), "%s/input0",
+		pwr->data->name);
+	idev->phys = pwr->phys;
+	idev->dev.parent = dev;
+	idev->id.bustype = BUS_I2C;
+
+	input_set_capability(idev, EV_KEY, KEY_POWER);
+
+	pwr->regmap = dev_get_regmap(dev->parent, NULL);
+	pwr->dev = dev;
+	pwr->idev = idev;
+	device_init_wakeup(dev, true);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return -EINVAL;
+
+	error = devm_request_threaded_irq(dev, irq, NULL, tps6521x_pb_irq,
+					  IRQF_TRIGGER_RISING |
+						IRQF_TRIGGER_FALLING |
+						IRQF_ONESHOT,
+					  pwr->data->name, pwr);
+	if (error) {
+		dev_err(dev, "failed to request IRQ #%d: %d\n", irq, error);
+		return error;
+	}
+
+	error= input_register_device(idev);
+	if (error) {
+		dev_err(dev, "Can't register power button: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct platform_device_id tps6521x_pwrbtn_id_table[] = {
+	{ "tps65218-pwrbutton", },
+	{ "tps65217-pwrbutton", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, tps6521x_pwrbtn_id_table);
+
+static struct platform_driver tps6521x_pb_driver = {
+	.probe	= tps6521x_pb_probe,
+	.driver	= {
+		.name	= "tps6521x_pwrbutton",
+		.of_match_table = of_tps6521x_pb_match,
+	},
+	.id_table = tps6521x_pwrbtn_id_table,
+};
+module_platform_driver(tps6521x_pb_driver);
+
+MODULE_DESCRIPTION("TPS6521X Power Button");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Felipe Balbi <balbi@ti.com>");