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, 272 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-syscon.c b/drivers/gpio/gpio-syscon.c
new file mode 100644
index 000000000..40064d4cf
--- /dev/null
+++ b/drivers/gpio/gpio-syscon.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  SYSCON GPIO driver
+ *
+ *  Copyright (C) 2014 Alexander Shiyan <shc_work@mail.ru>
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/driver.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+
+#define GPIO_SYSCON_FEAT_IN	BIT(0)
+#define GPIO_SYSCON_FEAT_OUT	BIT(1)
+#define GPIO_SYSCON_FEAT_DIR	BIT(2)
+
+/* SYSCON driver is designed to use 32-bit wide registers */
+#define SYSCON_REG_SIZE		(4)
+#define SYSCON_REG_BITS		(SYSCON_REG_SIZE * 8)
+
+/**
+ * struct syscon_gpio_data - Configuration for the device.
+ * @flags:		Set of GPIO_SYSCON_FEAT_ flags:
+ *			GPIO_SYSCON_FEAT_IN:	GPIOs supports input,
+ *			GPIO_SYSCON_FEAT_OUT:	GPIOs supports output,
+ *			GPIO_SYSCON_FEAT_DIR:	GPIOs supports switch direction.
+ * @bit_count:		Number of bits used as GPIOs.
+ * @dat_bit_offset:	Offset (in bits) to the first GPIO bit.
+ * @dir_bit_offset:	Optional offset (in bits) to the first bit to switch
+ *			GPIO direction (Used with GPIO_SYSCON_FEAT_DIR flag).
+ * @set:		HW specific callback to assigns output value
+ *			for signal "offset"
+ */
+
+struct syscon_gpio_data {
+	unsigned int	flags;
+	unsigned int	bit_count;
+	unsigned int	dat_bit_offset;
+	unsigned int	dir_bit_offset;
+	int		(*set)(struct gpio_chip *chip, unsigned int offset,
+			       int value);
+};
+
+struct syscon_gpio_priv {
+	struct gpio_chip		chip;
+	struct regmap			*syscon;
+	const struct syscon_gpio_data	*data;
+	u32				dreg_offset;
+	u32				dir_reg_offset;
+};
+
+static int syscon_gpio_get(struct gpio_chip *chip, unsigned offset)
+{
+	struct syscon_gpio_priv *priv = gpiochip_get_data(chip);
+	unsigned int val, offs;
+	int ret;
+
+	offs = priv->dreg_offset + priv->data->dat_bit_offset + offset;
+
+	ret = regmap_read(priv->syscon,
+			  (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE, &val);
+	if (ret)
+		return ret;
+
+	return !!(val & BIT(offs % SYSCON_REG_BITS));
+}
+
+static int syscon_gpio_set(struct gpio_chip *chip, unsigned int offset, int val)
+{
+	struct syscon_gpio_priv *priv = gpiochip_get_data(chip);
+	unsigned int offs;
+
+	offs = priv->dreg_offset + priv->data->dat_bit_offset + offset;
+
+	return regmap_update_bits(priv->syscon,
+				  (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
+				  BIT(offs % SYSCON_REG_BITS),
+				  val ? BIT(offs % SYSCON_REG_BITS) : 0);
+}
+
+static int syscon_gpio_dir_in(struct gpio_chip *chip, unsigned offset)
+{
+	struct syscon_gpio_priv *priv = gpiochip_get_data(chip);
+
+	if (priv->data->flags & GPIO_SYSCON_FEAT_DIR) {
+		unsigned int offs;
+
+		offs = priv->dir_reg_offset +
+		       priv->data->dir_bit_offset + offset;
+
+		regmap_update_bits(priv->syscon,
+				   (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
+				   BIT(offs % SYSCON_REG_BITS), 0);
+	}
+
+	return 0;
+}
+
+static int syscon_gpio_dir_out(struct gpio_chip *chip, unsigned offset, int val)
+{
+	struct syscon_gpio_priv *priv = gpiochip_get_data(chip);
+
+	if (priv->data->flags & GPIO_SYSCON_FEAT_DIR) {
+		unsigned int offs;
+
+		offs = priv->dir_reg_offset +
+		       priv->data->dir_bit_offset + offset;
+
+		regmap_update_bits(priv->syscon,
+				   (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
+				   BIT(offs % SYSCON_REG_BITS),
+				   BIT(offs % SYSCON_REG_BITS));
+	}
+
+	return chip->set(chip, offset, val);
+}
+
+static const struct syscon_gpio_data clps711x_mctrl_gpio = {
+	/* ARM CLPS711X SYSFLG1 Bits 8-10 */
+	.flags		= GPIO_SYSCON_FEAT_IN,
+	.bit_count	= 3,
+	.dat_bit_offset	= 0x40 * 8 + 8,
+};
+
+static int rockchip_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			     int val)
+{
+	struct syscon_gpio_priv *priv = gpiochip_get_data(chip);
+	unsigned int offs;
+	u8 bit;
+	u32 data;
+	int ret;
+
+	offs = priv->dreg_offset + priv->data->dat_bit_offset + offset;
+	bit = offs % SYSCON_REG_BITS;
+	data = (val ? BIT(bit) : 0) | BIT(bit + 16);
+	ret = regmap_write(priv->syscon,
+			   (offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
+			   data);
+	if (ret < 0)
+		dev_err(chip->parent, "gpio write failed ret(%d)\n", ret);
+
+	return ret;
+}
+
+static const struct syscon_gpio_data rockchip_rk3328_gpio_mute = {
+	/* RK3328 GPIO_MUTE is an output only pin at GRF_SOC_CON10[1] */
+	.flags		= GPIO_SYSCON_FEAT_OUT,
+	.bit_count	= 1,
+	.dat_bit_offset = 0x0428 * 8 + 1,
+	.set		= rockchip_gpio_set,
+};
+
+#define KEYSTONE_LOCK_BIT BIT(0)
+
+static int keystone_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			     int val)
+{
+	struct syscon_gpio_priv *priv = gpiochip_get_data(chip);
+	unsigned int offs;
+	int ret;
+
+	offs = priv->dreg_offset + priv->data->dat_bit_offset + offset;
+
+	if (!val)
+		return 0;
+
+	ret = regmap_update_bits(
+			priv->syscon,
+			(offs / SYSCON_REG_BITS) * SYSCON_REG_SIZE,
+			BIT(offs % SYSCON_REG_BITS) | KEYSTONE_LOCK_BIT,
+			BIT(offs % SYSCON_REG_BITS) | KEYSTONE_LOCK_BIT);
+	if (ret < 0)
+		dev_err(chip->parent, "gpio write failed ret(%d)\n", ret);
+
+	return ret;
+}
+
+static const struct syscon_gpio_data keystone_dsp_gpio = {
+	/* ARM Keystone 2 */
+	.flags		= GPIO_SYSCON_FEAT_OUT,
+	.bit_count	= 28,
+	.dat_bit_offset	= 4,
+	.set		= keystone_gpio_set,
+};
+
+static const struct of_device_id syscon_gpio_ids[] = {
+	{
+		.compatible	= "cirrus,ep7209-mctrl-gpio",
+		.data		= &clps711x_mctrl_gpio,
+	},
+	{
+		.compatible	= "ti,keystone-dsp-gpio",
+		.data		= &keystone_dsp_gpio,
+	},
+	{
+		.compatible	= "rockchip,rk3328-grf-gpio",
+		.data		= &rockchip_rk3328_gpio_mute,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, syscon_gpio_ids);
+
+static int syscon_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct syscon_gpio_priv *priv;
+	struct device_node *np = dev->of_node;
+	int ret;
+	bool use_parent_regmap = false;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->data = of_device_get_match_data(dev);
+
+	priv->syscon = syscon_regmap_lookup_by_phandle(np, "gpio,syscon-dev");
+	if (IS_ERR(priv->syscon) && np->parent) {
+		priv->syscon = syscon_node_to_regmap(np->parent);
+		use_parent_regmap = true;
+	}
+	if (IS_ERR(priv->syscon))
+		return PTR_ERR(priv->syscon);
+
+	if (!use_parent_regmap) {
+		ret = of_property_read_u32_index(np, "gpio,syscon-dev", 1,
+						 &priv->dreg_offset);
+		if (ret)
+			dev_err(dev, "can't read the data register offset!\n");
+
+		priv->dreg_offset <<= 3;
+
+		ret = of_property_read_u32_index(np, "gpio,syscon-dev", 2,
+						 &priv->dir_reg_offset);
+		if (ret)
+			dev_dbg(dev, "can't read the dir register offset!\n");
+
+		priv->dir_reg_offset <<= 3;
+	}
+
+	priv->chip.parent = dev;
+	priv->chip.owner = THIS_MODULE;
+	priv->chip.label = dev_name(dev);
+	priv->chip.base = -1;
+	priv->chip.ngpio = priv->data->bit_count;
+	priv->chip.get = syscon_gpio_get;
+	if (priv->data->flags & GPIO_SYSCON_FEAT_IN)
+		priv->chip.direction_input = syscon_gpio_dir_in;
+	if (priv->data->flags & GPIO_SYSCON_FEAT_OUT) {
+		priv->chip.set = priv->data->set ? : syscon_gpio_set;
+		priv->chip.direction_output = syscon_gpio_dir_out;
+	}
+
+	return devm_gpiochip_add_data(&pdev->dev, &priv->chip, priv);
+}
+
+static struct platform_driver syscon_gpio_driver = {
+	.driver	= {
+		.name		= "gpio-syscon",
+		.of_match_table	= syscon_gpio_ids,
+	},
+	.probe	= syscon_gpio_probe,
+};
+module_platform_driver(syscon_gpio_driver);
+
+MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
+MODULE_DESCRIPTION("SYSCON GPIO driver");
+MODULE_LICENSE("GPL");