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, 126 insertions, 0 deletions

diff --git a/drivers/mfd/lp87565.c b/drivers/mfd/lp87565.c
new file mode 100644
index 000000000..b78ae79df
--- /dev/null
+++ b/drivers/mfd/lp87565.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017 Texas Instruments Incorporated - https://www.ti.com/
+ *
+ * Author: Keerthy <j-keerthy@ti.com>
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <linux/mfd/lp87565.h>
+
+static const struct regmap_config lp87565_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = LP87565_REG_MAX,
+};
+
+static const struct mfd_cell lp87565_cells[] = {
+	{ .name = "lp87565-q1-regulator", },
+	{ .name = "lp87565-q1-gpio", },
+};
+
+static const struct of_device_id of_lp87565_match_table[] = {
+	{ .compatible = "ti,lp87565", },
+	{
+		.compatible = "ti,lp87524-q1",
+		.data = (void *)LP87565_DEVICE_TYPE_LP87524_Q1,
+	},
+	{
+		.compatible = "ti,lp87565-q1",
+		.data = (void *)LP87565_DEVICE_TYPE_LP87565_Q1,
+	},
+	{
+		.compatible = "ti,lp87561-q1",
+		.data = (void *)LP87565_DEVICE_TYPE_LP87561_Q1,
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, of_lp87565_match_table);
+
+static int lp87565_probe(struct i2c_client *client)
+{
+	struct lp87565 *lp87565;
+	int ret;
+	unsigned int otpid;
+
+	lp87565 = devm_kzalloc(&client->dev, sizeof(*lp87565), GFP_KERNEL);
+	if (!lp87565)
+		return -ENOMEM;
+
+	lp87565->dev = &client->dev;
+
+	lp87565->regmap = devm_regmap_init_i2c(client, &lp87565_regmap_config);
+	if (IS_ERR(lp87565->regmap)) {
+		ret = PTR_ERR(lp87565->regmap);
+		dev_err(lp87565->dev,
+			"Failed to initialize register map: %d\n", ret);
+		return ret;
+	}
+
+	lp87565->reset_gpio = devm_gpiod_get_optional(lp87565->dev, "reset",
+						      GPIOD_OUT_LOW);
+	if (IS_ERR(lp87565->reset_gpio)) {
+		ret = PTR_ERR(lp87565->reset_gpio);
+		if (ret == -EPROBE_DEFER)
+			return ret;
+	}
+
+	if (lp87565->reset_gpio) {
+		gpiod_set_value_cansleep(lp87565->reset_gpio, 1);
+		/* The minimum assertion time is undocumented, just guess */
+		usleep_range(2000, 4000);
+
+		gpiod_set_value_cansleep(lp87565->reset_gpio, 0);
+		/* Min 1.2 ms before first I2C transaction */
+		usleep_range(1500, 3000);
+	}
+
+	ret = regmap_read(lp87565->regmap, LP87565_REG_OTP_REV, &otpid);
+	if (ret) {
+		dev_err(lp87565->dev, "Failed to read OTP ID\n");
+		return ret;
+	}
+
+	lp87565->rev = otpid & LP87565_OTP_REV_OTP_ID;
+	lp87565->dev_type = (uintptr_t)i2c_get_match_data(client);
+
+	i2c_set_clientdata(client, lp87565);
+
+	return devm_mfd_add_devices(lp87565->dev, PLATFORM_DEVID_AUTO,
+				    lp87565_cells, ARRAY_SIZE(lp87565_cells),
+				    NULL, 0, NULL);
+}
+
+static void lp87565_shutdown(struct i2c_client *client)
+{
+	struct lp87565 *lp87565 = i2c_get_clientdata(client);
+
+	gpiod_set_value_cansleep(lp87565->reset_gpio, 1);
+}
+
+static const struct i2c_device_id lp87565_id_table[] = {
+	{ "lp87565-q1" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, lp87565_id_table);
+
+static struct i2c_driver lp87565_driver = {
+	.driver	= {
+		.name	= "lp87565",
+		.of_match_table = of_lp87565_match_table,
+	},
+	.probe = lp87565_probe,
+	.shutdown = lp87565_shutdown,
+	.id_table = lp87565_id_table,
+};
+module_i2c_driver(lp87565_driver);
+
+MODULE_AUTHOR("J Keerthy <j-keerthy@ti.com>");
+MODULE_DESCRIPTION("lp87565 chip family Multi-Function Device driver");
+MODULE_LICENSE("GPL v2");