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, 256 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/zet6223.c b/drivers/input/touchscreen/zet6223.c
new file mode 100644
index 000000000..a341142f3
--- /dev/null
+++ b/drivers/input/touchscreen/zet6223.c
@@ -0,0 +1,256 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2016, Jelle van der Waa <jelle@vdwaa.nl>
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/unaligned.h>
+
+#define ZET6223_MAX_FINGERS		16
+#define ZET6223_MAX_PKT_SIZE		(3 + 4 * ZET6223_MAX_FINGERS)
+
+#define ZET6223_CMD_INFO		0xB2
+#define ZET6223_CMD_INFO_LENGTH		17
+#define ZET6223_VALID_PACKET		0x3c
+
+#define ZET6223_POWER_ON_DELAY_MSEC	30
+
+struct zet6223_ts {
+	struct i2c_client *client;
+	struct input_dev *input;
+	struct touchscreen_properties prop;
+	struct regulator_bulk_data supplies[2];
+	u16 max_x;
+	u16 max_y;
+	u8 fingernum;
+};
+
+static int zet6223_start(struct input_dev *dev)
+{
+	struct zet6223_ts *ts = input_get_drvdata(dev);
+
+	enable_irq(ts->client->irq);
+
+	return 0;
+}
+
+static void zet6223_stop(struct input_dev *dev)
+{
+	struct zet6223_ts *ts = input_get_drvdata(dev);
+
+	disable_irq(ts->client->irq);
+}
+
+static irqreturn_t zet6223_irq(int irq, void *dev_id)
+{
+	struct zet6223_ts *ts = dev_id;
+	u16 finger_bits;
+
+	/*
+	 * First 3 bytes are an identifier, two bytes of finger data.
+	 * X, Y data per finger is 4 bytes.
+	 */
+	u8 bufsize = 3 + 4 * ts->fingernum;
+	u8 buf[ZET6223_MAX_PKT_SIZE];
+	int i;
+	int ret;
+	int error;
+
+	ret = i2c_master_recv(ts->client, buf, bufsize);
+	if (ret != bufsize) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err_ratelimited(&ts->client->dev,
+				    "Error reading input data: %d\n", error);
+		return IRQ_HANDLED;
+	}
+
+	if (buf[0] != ZET6223_VALID_PACKET)
+		return IRQ_HANDLED;
+
+	finger_bits = get_unaligned_be16(buf + 1);
+	for (i = 0; i < ts->fingernum; i++) {
+		if (!(finger_bits & BIT(15 - i)))
+			continue;
+
+		input_mt_slot(ts->input, i);
+		input_mt_report_slot_state(ts->input, MT_TOOL_FINGER, true);
+		input_event(ts->input, EV_ABS, ABS_MT_POSITION_X,
+				((buf[i + 3] >> 4) << 8) + buf[i + 4]);
+		input_event(ts->input, EV_ABS, ABS_MT_POSITION_Y,
+				((buf[i + 3] & 0xF) << 8) + buf[i + 5]);
+	}
+
+	input_mt_sync_frame(ts->input);
+	input_sync(ts->input);
+
+	return IRQ_HANDLED;
+}
+
+static void zet6223_power_off(void *_ts)
+{
+	struct zet6223_ts *ts = _ts;
+
+	regulator_bulk_disable(ARRAY_SIZE(ts->supplies), ts->supplies);
+}
+
+static int zet6223_power_on(struct zet6223_ts *ts)
+{
+	struct device *dev = &ts->client->dev;
+	int error;
+
+	ts->supplies[0].supply = "vio";
+	ts->supplies[1].supply = "vcc";
+
+	error = devm_regulator_bulk_get(dev, ARRAY_SIZE(ts->supplies),
+					ts->supplies);
+	if (error)
+		return error;
+
+	error = regulator_bulk_enable(ARRAY_SIZE(ts->supplies), ts->supplies);
+	if (error)
+		return error;
+
+	msleep(ZET6223_POWER_ON_DELAY_MSEC);
+
+	error = devm_add_action_or_reset(dev, zet6223_power_off, ts);
+	if (error) {
+		dev_err(dev, "failed to install poweroff action: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int zet6223_query_device(struct zet6223_ts *ts)
+{
+	u8 buf[ZET6223_CMD_INFO_LENGTH];
+	u8 cmd = ZET6223_CMD_INFO;
+	int ret;
+	int error;
+
+	ret = i2c_master_send(ts->client, &cmd, sizeof(cmd));
+	if (ret != sizeof(cmd)) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err(&ts->client->dev,
+			"touchpanel info cmd failed: %d\n", error);
+		return error;
+	}
+
+	ret = i2c_master_recv(ts->client, buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
+		error = ret < 0 ? ret : -EIO;
+		dev_err(&ts->client->dev,
+			"failed to retrieve touchpanel info: %d\n", error);
+		return error;
+	}
+
+	ts->fingernum = buf[15] & 0x7F;
+	if (ts->fingernum > ZET6223_MAX_FINGERS) {
+		dev_warn(&ts->client->dev,
+			 "touchpanel reports %d fingers, limiting to %d\n",
+			 ts->fingernum, ZET6223_MAX_FINGERS);
+		ts->fingernum = ZET6223_MAX_FINGERS;
+	}
+
+	ts->max_x = get_unaligned_le16(&buf[8]);
+	ts->max_y = get_unaligned_le16(&buf[10]);
+
+	return 0;
+}
+
+static int zet6223_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct zet6223_ts *ts;
+	struct input_dev *input;
+	int error;
+
+	if (!client->irq) {
+		dev_err(dev, "no irq specified\n");
+		return -EINVAL;
+	}
+
+	ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	ts->client = client;
+
+	error = zet6223_power_on(ts);
+	if (error)
+		return error;
+
+	error = zet6223_query_device(ts);
+	if (error)
+		return error;
+
+	ts->input = input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	input_set_drvdata(input, ts);
+
+	input->name = client->name;
+	input->id.bustype = BUS_I2C;
+	input->open = zet6223_start;
+	input->close = zet6223_stop;
+
+	input_set_abs_params(input, ABS_MT_POSITION_X, 0, ts->max_x, 0, 0);
+	input_set_abs_params(input, ABS_MT_POSITION_Y, 0, ts->max_y, 0, 0);
+
+	touchscreen_parse_properties(input, true, &ts->prop);
+
+	error = input_mt_init_slots(input, ts->fingernum,
+				    INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
+	if (error)
+		return error;
+
+	error = devm_request_threaded_irq(dev, client->irq, NULL, zet6223_irq,
+					  IRQF_ONESHOT, client->name, ts);
+	if (error) {
+		dev_err(dev, "failed to request irq %d: %d\n",
+			client->irq, error);
+		return error;
+	}
+
+	zet6223_stop(input);
+
+	error = input_register_device(input);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static const struct of_device_id zet6223_of_match[] = {
+	{ .compatible = "zeitec,zet6223" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, zet6223_of_match);
+
+static const struct i2c_device_id zet6223_id[] = {
+	{ .name = "zet6223" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, zet6223_id);
+
+static struct i2c_driver zet6223_driver = {
+	.driver = {
+		.name = "zet6223",
+		.of_match_table = zet6223_of_match,
+	},
+	.probe = zet6223_probe,
+	.id_table = zet6223_id
+};
+module_i2c_driver(zet6223_driver);
+
+MODULE_AUTHOR("Jelle van der Waa <jelle@vdwaa.nl>");
+MODULE_DESCRIPTION("ZEITEC zet622x I2C touchscreen driver");
+MODULE_LICENSE("GPL");