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, 308 insertions, 0 deletions

diff --git a/drivers/misc/apds9802als.c b/drivers/misc/apds9802als.c
new file mode 100644
index 000000000..1488e2881
--- /dev/null
+++ b/drivers/misc/apds9802als.c
@@ -0,0 +1,308 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * apds9802als.c - apds9802  ALS Driver
+ *
+ * Copyright (C) 2009 Intel Corp
+ *
+ *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+#include <linux/pm_runtime.h>
+
+#define ALS_MIN_RANGE_VAL 1
+#define ALS_MAX_RANGE_VAL 2
+#define POWER_STA_ENABLE 1
+#define POWER_STA_DISABLE 0
+
+#define DRIVER_NAME "apds9802als"
+
+struct als_data {
+	struct mutex mutex;
+};
+
+static ssize_t als_sensing_range_show(struct device *dev,
+			struct device_attribute *attr,  char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int  val;
+
+	val = i2c_smbus_read_byte_data(client, 0x81);
+	if (val < 0)
+		return val;
+	if (val & 1)
+		return sprintf(buf, "4095\n");
+	else
+		return sprintf(buf, "65535\n");
+}
+
+static int als_wait_for_data_ready(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	int ret;
+	int retry = 10;
+
+	do {
+		msleep(30);
+		ret = i2c_smbus_read_byte_data(client, 0x86);
+	} while (!(ret & 0x80) && retry--);
+
+	if (retry < 0) {
+		dev_warn(dev, "timeout waiting for data ready\n");
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static ssize_t als_lux0_input_data_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct als_data *data = i2c_get_clientdata(client);
+	int ret_val;
+	int temp;
+
+	/* Protect against parallel reads */
+	pm_runtime_get_sync(dev);
+	mutex_lock(&data->mutex);
+
+	/* clear EOC interrupt status */
+	i2c_smbus_write_byte(client, 0x40);
+	/* start measurement */
+	temp = i2c_smbus_read_byte_data(client, 0x81);
+	i2c_smbus_write_byte_data(client, 0x81, temp | 0x08);
+
+	ret_val = als_wait_for_data_ready(dev);
+	if (ret_val < 0)
+		goto failed;
+
+	temp = i2c_smbus_read_byte_data(client, 0x8C); /* LSB data */
+	if (temp < 0) {
+		ret_val = temp;
+		goto failed;
+	}
+	ret_val = i2c_smbus_read_byte_data(client, 0x8D); /* MSB data */
+	if (ret_val < 0)
+		goto failed;
+
+	mutex_unlock(&data->mutex);
+	pm_runtime_put_sync(dev);
+
+	temp = (ret_val << 8) | temp;
+	return sprintf(buf, "%d\n", temp);
+failed:
+	mutex_unlock(&data->mutex);
+	pm_runtime_put_sync(dev);
+	return ret_val;
+}
+
+static ssize_t als_sensing_range_store(struct device *dev,
+		struct device_attribute *attr, const  char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct als_data *data = i2c_get_clientdata(client);
+	int ret_val;
+	unsigned long val;
+
+	ret_val = kstrtoul(buf, 10, &val);
+	if (ret_val)
+		return ret_val;
+
+	if (val < 4096)
+		val = 1;
+	else if (val < 65536)
+		val = 2;
+	else
+		return -ERANGE;
+
+	pm_runtime_get_sync(dev);
+
+	/* Make sure nobody else reads/modifies/writes 0x81 while we
+	   are active */
+	mutex_lock(&data->mutex);
+
+	ret_val = i2c_smbus_read_byte_data(client, 0x81);
+	if (ret_val < 0)
+		goto fail;
+
+	/* Reset the bits before setting them */
+	ret_val = ret_val & 0xFA;
+
+	if (val == 1) /* Setting detection range up to 4k LUX */
+		ret_val = (ret_val | 0x01);
+	else /* Setting detection range up to 64k LUX*/
+		ret_val = (ret_val | 0x00);
+
+	ret_val = i2c_smbus_write_byte_data(client, 0x81, ret_val);
+
+	if (ret_val >= 0) {
+		/* All OK */
+		mutex_unlock(&data->mutex);
+		pm_runtime_put_sync(dev);
+		return count;
+	}
+fail:
+	mutex_unlock(&data->mutex);
+	pm_runtime_put_sync(dev);
+	return ret_val;
+}
+
+static int als_set_power_state(struct i2c_client *client, bool on_off)
+{
+	int ret_val;
+	struct als_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->mutex);
+	ret_val = i2c_smbus_read_byte_data(client, 0x80);
+	if (ret_val < 0)
+		goto fail;
+	if (on_off)
+		ret_val = ret_val | 0x01;
+	else
+		ret_val = ret_val & 0xFE;
+	ret_val = i2c_smbus_write_byte_data(client, 0x80, ret_val);
+fail:
+	mutex_unlock(&data->mutex);
+	return ret_val;
+}
+
+static DEVICE_ATTR(lux0_sensor_range, S_IRUGO | S_IWUSR,
+	als_sensing_range_show, als_sensing_range_store);
+static DEVICE_ATTR(lux0_input, S_IRUGO, als_lux0_input_data_show, NULL);
+
+static struct attribute *mid_att_als[] = {
+	&dev_attr_lux0_sensor_range.attr,
+	&dev_attr_lux0_input.attr,
+	NULL
+};
+
+static const struct attribute_group m_als_gr = {
+	.name = "apds9802als",
+	.attrs = mid_att_als
+};
+
+static int als_set_default_config(struct i2c_client *client)
+{
+	int ret_val;
+	/* Write the command and then switch on */
+	ret_val = i2c_smbus_write_byte_data(client, 0x80, 0x01);
+	if (ret_val < 0) {
+		dev_err(&client->dev, "failed default switch on write\n");
+		return ret_val;
+	}
+	/* detection range: 1~64K Lux, maunal measurement */
+	ret_val = i2c_smbus_write_byte_data(client, 0x81, 0x08);
+	if (ret_val < 0)
+		dev_err(&client->dev, "failed default LUX on write\n");
+
+	/*  We always get 0 for the 1st measurement after system power on,
+	 *  so make sure it is finished before user asks for data.
+	 */
+	als_wait_for_data_ready(&client->dev);
+
+	return ret_val;
+}
+
+static int apds9802als_probe(struct i2c_client *client)
+{
+	int res;
+	struct als_data *data;
+
+	data = kzalloc_obj(struct als_data);
+	if (data == NULL) {
+		dev_err(&client->dev, "Memory allocation failed\n");
+		return -ENOMEM;
+	}
+	i2c_set_clientdata(client, data);
+	res = sysfs_create_group(&client->dev.kobj, &m_als_gr);
+	if (res) {
+		dev_err(&client->dev, "device create file failed\n");
+		goto als_error1;
+	}
+	dev_info(&client->dev, "ALS chip found\n");
+	als_set_default_config(client);
+	mutex_init(&data->mutex);
+
+	pm_runtime_set_active(&client->dev);
+	pm_runtime_enable(&client->dev);
+
+	return res;
+als_error1:
+	kfree(data);
+	return res;
+}
+
+static void apds9802als_remove(struct i2c_client *client)
+{
+	struct als_data *data = i2c_get_clientdata(client);
+
+	pm_runtime_get_sync(&client->dev);
+
+	als_set_power_state(client, false);
+	sysfs_remove_group(&client->dev.kobj, &m_als_gr);
+
+	pm_runtime_disable(&client->dev);
+	pm_runtime_set_suspended(&client->dev);
+	pm_runtime_put_noidle(&client->dev);
+
+	kfree(data);
+}
+
+#ifdef CONFIG_PM
+
+static int apds9802als_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	als_set_power_state(client, false);
+	return 0;
+}
+
+static int apds9802als_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+
+	als_set_power_state(client, true);
+	return 0;
+}
+
+static UNIVERSAL_DEV_PM_OPS(apds9802als_pm_ops, apds9802als_suspend,
+	apds9802als_resume, NULL);
+
+#define APDS9802ALS_PM_OPS (&apds9802als_pm_ops)
+
+#else	/* CONFIG_PM */
+#define APDS9802ALS_PM_OPS NULL
+#endif	/* CONFIG_PM */
+
+static const struct i2c_device_id apds9802als_id[] = {
+	{ .name = DRIVER_NAME },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, apds9802als_id);
+
+static struct i2c_driver apds9802als_driver = {
+	.driver = {
+		.name = DRIVER_NAME,
+		.pm = APDS9802ALS_PM_OPS,
+	},
+	.probe = apds9802als_probe,
+	.remove = apds9802als_remove,
+	.id_table = apds9802als_id,
+};
+
+module_i2c_driver(apds9802als_driver);
+
+MODULE_AUTHOR("Anantha Narayanan <Anantha.Narayanan@intel.com");
+MODULE_DESCRIPTION("Avago apds9802als ALS Driver");
+MODULE_LICENSE("GPL v2");