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, 129 insertions, 0 deletions

diff --git a/drivers/input/misc/max77650-onkey.c b/drivers/input/misc/max77650-onkey.c
new file mode 100644
index 000000000..ee55f22db
--- /dev/null
+++ b/drivers/input/misc/max77650-onkey.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright (C) 2018 BayLibre SAS
+// Author: Bartosz Golaszewski <bgolaszewski@baylibre.com>
+//
+// ONKEY driver for MAXIM 77650/77651 charger/power-supply.
+
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/max77650.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define MAX77650_ONKEY_MODE_MASK	BIT(3)
+#define MAX77650_ONKEY_MODE_PUSH	0x00
+#define MAX77650_ONKEY_MODE_SLIDE	BIT(3)
+
+struct max77650_onkey {
+	struct input_dev *input;
+	unsigned int code;
+};
+
+static irqreturn_t max77650_onkey_falling(int irq, void *data)
+{
+	struct max77650_onkey *onkey = data;
+
+	input_report_key(onkey->input, onkey->code, 0);
+	input_sync(onkey->input);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t max77650_onkey_rising(int irq, void *data)
+{
+	struct max77650_onkey *onkey = data;
+
+	input_report_key(onkey->input, onkey->code, 1);
+	input_sync(onkey->input);
+
+	return IRQ_HANDLED;
+}
+
+static int max77650_onkey_probe(struct platform_device *pdev)
+{
+	int irq_r, irq_f, error, mode;
+	struct max77650_onkey *onkey;
+	struct device *dev, *parent;
+	struct regmap *map;
+	unsigned int type;
+
+	dev = &pdev->dev;
+	parent = dev->parent;
+
+	map = dev_get_regmap(parent, NULL);
+	if (!map)
+		return -ENODEV;
+
+	onkey = devm_kzalloc(dev, sizeof(*onkey), GFP_KERNEL);
+	if (!onkey)
+		return -ENOMEM;
+
+	error = device_property_read_u32(dev, "linux,code", &onkey->code);
+	if (error)
+		onkey->code = KEY_POWER;
+
+	if (device_property_read_bool(dev, "maxim,onkey-slide")) {
+		mode = MAX77650_ONKEY_MODE_SLIDE;
+		type = EV_SW;
+	} else {
+		mode = MAX77650_ONKEY_MODE_PUSH;
+		type = EV_KEY;
+	}
+
+	error = regmap_update_bits(map, MAX77650_REG_CNFG_GLBL,
+				   MAX77650_ONKEY_MODE_MASK, mode);
+	if (error)
+		return error;
+
+	irq_f = platform_get_irq_byname(pdev, "nEN_F");
+	if (irq_f < 0)
+		return irq_f;
+
+	irq_r = platform_get_irq_byname(pdev, "nEN_R");
+	if (irq_r < 0)
+		return irq_r;
+
+	onkey->input = devm_input_allocate_device(dev);
+	if (!onkey->input)
+		return -ENOMEM;
+
+	onkey->input->name = "max77650_onkey";
+	onkey->input->phys = "max77650_onkey/input0";
+	onkey->input->id.bustype = BUS_I2C;
+	input_set_capability(onkey->input, type, onkey->code);
+
+	error = devm_request_any_context_irq(dev, irq_f, max77650_onkey_falling,
+					     IRQF_ONESHOT, "onkey-down", onkey);
+	if (error < 0)
+		return error;
+
+	error = devm_request_any_context_irq(dev, irq_r, max77650_onkey_rising,
+					     IRQF_ONESHOT, "onkey-up", onkey);
+	if (error < 0)
+		return error;
+
+	return input_register_device(onkey->input);
+}
+
+static const struct of_device_id max77650_onkey_of_match[] = {
+	{ .compatible = "maxim,max77650-onkey" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max77650_onkey_of_match);
+
+static struct platform_driver max77650_onkey_driver = {
+	.driver = {
+		.name = "max77650-onkey",
+		.of_match_table = max77650_onkey_of_match,
+	},
+	.probe = max77650_onkey_probe,
+};
+module_platform_driver(max77650_onkey_driver);
+
+MODULE_DESCRIPTION("MAXIM 77650/77651 ONKEY driver");
+MODULE_AUTHOR("Bartosz Golaszewski <bgolaszewski@baylibre.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:max77650-onkey");