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, 163 insertions, 0 deletions

diff --git a/drivers/usb/phy/phy-isp1301.c b/drivers/usb/phy/phy-isp1301.c
new file mode 100644
index 000000000..73cc70e95
--- /dev/null
+++ b/drivers/usb/phy/phy-isp1301.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * NXP ISP1301 USB transceiver driver
+ *
+ * Copyright (C) 2012 Roland Stigge
+ *
+ * Author: Roland Stigge <stigge@antcom.de>
+ */
+
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/i2c.h>
+#include <linux/usb/phy.h>
+#include <linux/usb/isp1301.h>
+
+#define DRV_NAME		"isp1301"
+
+struct isp1301 {
+	struct usb_phy		phy;
+	struct mutex		mutex;
+
+	struct i2c_client	*client;
+};
+
+#define phy_to_isp(p)		(container_of((p), struct isp1301, phy))
+
+static const struct i2c_device_id isp1301_id[] = {
+	{ .name = "isp1301" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, isp1301_id);
+
+static const struct of_device_id isp1301_of_match[] = {
+	{.compatible = "nxp,isp1301" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, isp1301_of_match);
+
+static struct i2c_client *isp1301_i2c_client;
+
+static int __isp1301_write(struct isp1301 *isp, u8 reg, u8 value, u8 clear)
+{
+	return i2c_smbus_write_byte_data(isp->client, reg | clear, value);
+}
+
+static int isp1301_write(struct isp1301 *isp, u8 reg, u8 value)
+{
+	return __isp1301_write(isp, reg, value, 0);
+}
+
+static int isp1301_clear(struct isp1301 *isp, u8 reg, u8 value)
+{
+	return __isp1301_write(isp, reg, value, ISP1301_I2C_REG_CLEAR_ADDR);
+}
+
+static int isp1301_phy_init(struct usb_phy *phy)
+{
+	struct isp1301 *isp = phy_to_isp(phy);
+
+	/* Disable transparent UART mode first */
+	isp1301_clear(isp, ISP1301_I2C_MODE_CONTROL_1, MC1_UART_EN);
+	isp1301_clear(isp, ISP1301_I2C_MODE_CONTROL_1, ~MC1_SPEED_REG);
+	isp1301_write(isp, ISP1301_I2C_MODE_CONTROL_1, MC1_SPEED_REG);
+	isp1301_clear(isp, ISP1301_I2C_MODE_CONTROL_2, ~0);
+	isp1301_write(isp, ISP1301_I2C_MODE_CONTROL_2, (MC2_BI_DI | MC2_PSW_EN
+				| MC2_SPD_SUSP_CTRL));
+
+	isp1301_clear(isp, ISP1301_I2C_OTG_CONTROL_1, ~0);
+	isp1301_write(isp, ISP1301_I2C_MODE_CONTROL_1, MC1_DAT_SE0);
+	isp1301_write(isp, ISP1301_I2C_OTG_CONTROL_1, (OTG1_DM_PULLDOWN
+				| OTG1_DP_PULLDOWN));
+	isp1301_clear(isp, ISP1301_I2C_OTG_CONTROL_1, (OTG1_DM_PULLUP
+				| OTG1_DP_PULLUP));
+
+	/* mask all interrupts */
+	isp1301_clear(isp, ISP1301_I2C_INTERRUPT_LATCH, ~0);
+	isp1301_clear(isp, ISP1301_I2C_INTERRUPT_FALLING, ~0);
+	isp1301_clear(isp, ISP1301_I2C_INTERRUPT_RISING, ~0);
+
+	return 0;
+}
+
+static int isp1301_phy_set_vbus(struct usb_phy *phy, int on)
+{
+	struct isp1301 *isp = phy_to_isp(phy);
+
+	if (on)
+		isp1301_write(isp, ISP1301_I2C_OTG_CONTROL_1, OTG1_VBUS_DRV);
+	else
+		isp1301_clear(isp, ISP1301_I2C_OTG_CONTROL_1, OTG1_VBUS_DRV);
+
+	return 0;
+}
+
+static int isp1301_probe(struct i2c_client *client)
+{
+	struct isp1301 *isp;
+	struct usb_phy *phy;
+
+	isp = devm_kzalloc(&client->dev, sizeof(*isp), GFP_KERNEL);
+	if (!isp)
+		return -ENOMEM;
+
+	isp->client = client;
+	mutex_init(&isp->mutex);
+
+	phy = &isp->phy;
+	phy->dev = &client->dev;
+	phy->label = DRV_NAME;
+	phy->init = isp1301_phy_init;
+	phy->set_vbus = isp1301_phy_set_vbus;
+	phy->type = USB_PHY_TYPE_USB2;
+
+	i2c_set_clientdata(client, isp);
+	usb_add_phy_dev(phy);
+
+	isp1301_i2c_client = client;
+
+	return 0;
+}
+
+static void isp1301_remove(struct i2c_client *client)
+{
+	struct isp1301 *isp = i2c_get_clientdata(client);
+
+	usb_remove_phy(&isp->phy);
+	isp1301_i2c_client = NULL;
+}
+
+static struct i2c_driver isp1301_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.of_match_table = isp1301_of_match,
+	},
+	.probe = isp1301_probe,
+	.remove = isp1301_remove,
+	.id_table = isp1301_id,
+};
+
+module_i2c_driver(isp1301_driver);
+
+struct i2c_client *isp1301_get_client(struct device_node *node)
+{
+	struct i2c_client *client;
+
+	/* reference of ISP1301 I2C node via DT */
+	client = of_find_i2c_device_by_node(node);
+	if (client)
+		return client;
+
+	/* non-DT: only one ISP1301 chip supported */
+	if (isp1301_i2c_client) {
+		get_device(&isp1301_i2c_client->dev);
+		return isp1301_i2c_client;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(isp1301_get_client);
+
+MODULE_AUTHOR("Roland Stigge <stigge@antcom.de>");
+MODULE_DESCRIPTION("NXP ISP1301 USB transceiver driver");
+MODULE_LICENSE("GPL");