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, 205 insertions, 0 deletions

diff --git a/drivers/input/keyboard/adc-keys.c b/drivers/input/keyboard/adc-keys.c
new file mode 100644
index 000000000..d687459a0
--- /dev/null
+++ b/drivers/input/keyboard/adc-keys.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Input driver for resistor ladder connected on ADC
+ *
+ * Copyright (c) 2016 Alexandre Belloni
+ */
+
+#include <linux/err.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/types.h>
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+struct adc_keys_button {
+	u32 voltage;
+	u32 keycode;
+};
+
+struct adc_keys_state {
+	struct iio_channel *channel;
+	u32 num_keys;
+	u32 last_key;
+	u32 keyup_voltage;
+	const struct adc_keys_button *map;
+};
+
+static void adc_keys_poll(struct input_dev *input)
+{
+	struct adc_keys_state *st = input_get_drvdata(input);
+	int i, value, ret;
+	u32 diff, closest = 0xffffffff;
+	int keycode = 0;
+
+	ret = iio_read_channel_processed(st->channel, &value);
+	if (unlikely(ret < 0)) {
+		/* Forcibly release key if any was pressed */
+		value = st->keyup_voltage;
+	} else {
+		for (i = 0; i < st->num_keys; i++) {
+			diff = abs(st->map[i].voltage - value);
+			if (diff < closest) {
+				closest = diff;
+				keycode = st->map[i].keycode;
+			}
+		}
+	}
+
+	if (abs(st->keyup_voltage - value) < closest)
+		keycode = 0;
+
+	if (st->last_key && st->last_key != keycode)
+		input_report_key(input, st->last_key, 0);
+
+	if (keycode)
+		input_report_key(input, keycode, 1);
+
+	input_sync(input);
+	st->last_key = keycode;
+}
+
+static int adc_keys_load_keymap(struct device *dev, struct adc_keys_state *st)
+{
+	struct adc_keys_button *map;
+	int i;
+
+	st->num_keys = device_get_child_node_count(dev);
+	if (st->num_keys == 0) {
+		dev_err(dev, "keymap is missing\n");
+		return -EINVAL;
+	}
+
+	map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
+	if (!map)
+		return -ENOMEM;
+
+	i = 0;
+	device_for_each_child_node_scoped(dev, child) {
+		if (fwnode_property_read_u32(child, "press-threshold-microvolt",
+					     &map[i].voltage)) {
+			dev_err(dev, "Key with invalid or missing voltage\n");
+			return -EINVAL;
+		}
+		map[i].voltage /= 1000;
+
+		if (fwnode_property_read_u32(child, "linux,code",
+					     &map[i].keycode)) {
+			dev_err(dev, "Key with invalid or missing linux,code\n");
+			return -EINVAL;
+		}
+
+		i++;
+	}
+
+	st->map = map;
+	return 0;
+}
+
+static int adc_keys_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct adc_keys_state *st;
+	struct input_dev *input;
+	enum iio_chan_type type;
+	int i, value;
+	int error;
+
+	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
+	if (!st)
+		return -ENOMEM;
+
+	st->channel = devm_iio_channel_get(dev, "buttons");
+	if (IS_ERR(st->channel))
+		return PTR_ERR(st->channel);
+
+	if (!st->channel->indio_dev)
+		return -ENXIO;
+
+	error = iio_get_channel_type(st->channel, &type);
+	if (error < 0)
+		return error;
+
+	if (type != IIO_VOLTAGE) {
+		dev_err(dev, "Incompatible channel type %d\n", type);
+		return -EINVAL;
+	}
+
+	if (device_property_read_u32(dev, "keyup-threshold-microvolt",
+				     &st->keyup_voltage)) {
+		dev_err(dev, "Invalid or missing keyup voltage\n");
+		return -EINVAL;
+	}
+	st->keyup_voltage /= 1000;
+
+	error = adc_keys_load_keymap(dev, st);
+	if (error)
+		return error;
+
+	input = devm_input_allocate_device(dev);
+	if (!input) {
+		dev_err(dev, "failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	input_set_drvdata(input, st);
+
+	input->name = pdev->name;
+	input->phys = "adc-keys/input0";
+
+	input->id.bustype = BUS_HOST;
+	input->id.vendor = 0x0001;
+	input->id.product = 0x0001;
+	input->id.version = 0x0100;
+
+	__set_bit(EV_KEY, input->evbit);
+	for (i = 0; i < st->num_keys; i++)
+		__set_bit(st->map[i].keycode, input->keybit);
+
+	if (device_property_read_bool(dev, "autorepeat"))
+		__set_bit(EV_REP, input->evbit);
+
+
+	error = input_setup_polling(input, adc_keys_poll);
+	if (error) {
+		dev_err(dev, "Unable to set up polling: %d\n", error);
+		return error;
+	}
+
+	if (!device_property_read_u32(dev, "poll-interval", &value))
+		input_set_poll_interval(input, value);
+
+	error = input_register_device(input);
+	if (error) {
+		dev_err(dev, "Unable to register input device: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id adc_keys_of_match[] = {
+	{ .compatible = "adc-keys", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, adc_keys_of_match);
+#endif
+
+static struct platform_driver adc_keys_driver = {
+	.driver = {
+		.name = "adc_keys",
+		.of_match_table = of_match_ptr(adc_keys_of_match),
+	},
+	.probe = adc_keys_probe,
+};
+module_platform_driver(adc_keys_driver);
+
+MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
+MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
+MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS("IIO_CONSUMER");