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, 348 insertions, 0 deletions

diff --git a/drivers/usb/phy/phy-generic.c b/drivers/usb/phy/phy-generic.c
new file mode 100644
index 000000000..de26b3023
--- /dev/null
+++ b/drivers/usb/phy/phy-generic.c
@@ -0,0 +1,348 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NOP USB transceiver for all USB transceiver which are either built-in
+ * into USB IP or which are mostly autonomous.
+ *
+ * Copyright (C) 2009 Texas Instruments Inc
+ * Author: Ajay Kumar Gupta <ajay.gupta@ti.com>
+ *
+ * Current status:
+ *	This provides a "nop" transceiver for PHYs which are
+ *	autonomous such as isp1504, isp1707, etc.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/otg.h>
+#include <linux/usb/usb_phy_generic.h>
+#include <linux/slab.h>
+#include <linux/clk.h>
+#include <linux/regulator/consumer.h>
+#include <linux/property.h>
+#include <linux/gpio/consumer.h>
+#include <linux/delay.h>
+
+#include "phy-generic.h"
+
+#define VBUS_IRQ_FLAGS \
+	(IRQF_SHARED | IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | \
+		IRQF_ONESHOT)
+
+struct platform_device *usb_phy_generic_register(void)
+{
+	return platform_device_register_simple("usb_phy_generic",
+			PLATFORM_DEVID_AUTO, NULL, 0);
+}
+EXPORT_SYMBOL_GPL(usb_phy_generic_register);
+
+void usb_phy_generic_unregister(struct platform_device *pdev)
+{
+	platform_device_unregister(pdev);
+}
+EXPORT_SYMBOL_GPL(usb_phy_generic_unregister);
+
+static int nop_set_suspend(struct usb_phy *x, int suspend)
+{
+	struct usb_phy_generic *nop = dev_get_drvdata(x->dev);
+	int ret = 0;
+
+	if (suspend) {
+		clk_disable_unprepare(nop->clk);
+		if (!IS_ERR(nop->vcc) && !device_may_wakeup(x->dev))
+			ret = regulator_disable(nop->vcc);
+	} else {
+		if (!IS_ERR(nop->vcc) && !device_may_wakeup(x->dev))
+			ret = regulator_enable(nop->vcc);
+		clk_prepare_enable(nop->clk);
+	}
+
+	return ret;
+}
+
+static void nop_reset(struct usb_phy_generic *nop)
+{
+	if (!nop->gpiod_reset)
+		return;
+
+	gpiod_set_value_cansleep(nop->gpiod_reset, 1);
+	usleep_range(10000, 20000);
+	gpiod_set_value_cansleep(nop->gpiod_reset, 0);
+	usleep_range(10000, 30000);
+}
+
+/* interface to regulator framework */
+static int nop_set_vbus(struct usb_otg *otg, bool enable)
+{
+	int ret = 0;
+	struct usb_phy_generic *nop = dev_get_drvdata(otg->usb_phy->dev);
+
+	if (!nop->vbus_draw)
+		return 0;
+
+	if (enable && !nop->vbus_draw_enabled) {
+		ret = regulator_enable(nop->vbus_draw);
+		if (ret)
+			nop->vbus_draw_enabled = false;
+		else
+			nop->vbus_draw_enabled = true;
+
+	} else if (!enable && nop->vbus_draw_enabled) {
+		ret = regulator_disable(nop->vbus_draw);
+		nop->vbus_draw_enabled = false;
+	}
+	return ret;
+}
+
+
+static irqreturn_t nop_gpio_vbus_thread(int irq, void *data)
+{
+	struct usb_phy_generic *nop = data;
+	struct usb_otg *otg = nop->phy.otg;
+	int vbus, status;
+
+	vbus = gpiod_get_value(nop->gpiod_vbus);
+	if ((vbus ^ nop->vbus) == 0)
+		return IRQ_HANDLED;
+	nop->vbus = vbus;
+
+	if (vbus) {
+		status = USB_EVENT_VBUS;
+		otg->state = OTG_STATE_B_PERIPHERAL;
+		nop->phy.last_event = status;
+
+		atomic_notifier_call_chain(&nop->phy.notifier, status,
+					   otg->gadget);
+	} else {
+		status = USB_EVENT_NONE;
+		otg->state = OTG_STATE_B_IDLE;
+		nop->phy.last_event = status;
+
+		atomic_notifier_call_chain(&nop->phy.notifier, status,
+					   otg->gadget);
+	}
+	return IRQ_HANDLED;
+}
+
+int usb_gen_phy_init(struct usb_phy *phy)
+{
+	struct usb_phy_generic *nop = dev_get_drvdata(phy->dev);
+	int ret;
+
+	if (!IS_ERR(nop->vcc)) {
+		if (regulator_enable(nop->vcc))
+			dev_err(phy->dev, "Failed to enable power\n");
+	}
+
+	ret = clk_prepare_enable(nop->clk);
+	if (ret)
+		return ret;
+
+	nop_reset(nop);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_gen_phy_init);
+
+void usb_gen_phy_shutdown(struct usb_phy *phy)
+{
+	struct usb_phy_generic *nop = dev_get_drvdata(phy->dev);
+
+	gpiod_set_value_cansleep(nop->gpiod_reset, 1);
+
+	clk_disable_unprepare(nop->clk);
+
+	if (!IS_ERR(nop->vcc)) {
+		if (regulator_disable(nop->vcc))
+			dev_err(phy->dev, "Failed to disable power\n");
+	}
+}
+EXPORT_SYMBOL_GPL(usb_gen_phy_shutdown);
+
+static int nop_set_peripheral(struct usb_otg *otg, struct usb_gadget *gadget)
+{
+	if (!otg)
+		return -ENODEV;
+
+	if (!gadget) {
+		otg->gadget = NULL;
+		return -ENODEV;
+	}
+
+	otg->gadget = gadget;
+	if (otg->state == OTG_STATE_B_PERIPHERAL)
+		atomic_notifier_call_chain(&otg->usb_phy->notifier,
+					   USB_EVENT_VBUS, otg->gadget);
+	else
+		otg->state = OTG_STATE_B_IDLE;
+	return 0;
+}
+
+static int nop_set_host(struct usb_otg *otg, struct usb_bus *host)
+{
+	if (!otg)
+		return -ENODEV;
+
+	if (!host) {
+		otg->host = NULL;
+		return -ENODEV;
+	}
+
+	otg->host = host;
+	return 0;
+}
+
+int usb_phy_gen_create_phy(struct device *dev, struct usb_phy_generic *nop)
+{
+	enum usb_phy_type type = USB_PHY_TYPE_USB2;
+	int err = 0;
+	u32 clk_rate = 0;
+
+	device_property_read_u32(dev, "clock-frequency", &clk_rate);
+	nop->gpiod_reset = devm_gpiod_get_optional(dev, "reset",
+						   GPIOD_ASIS);
+	err = PTR_ERR_OR_ZERO(nop->gpiod_reset);
+	if (!err) {
+		nop->gpiod_vbus = devm_gpiod_get_optional(dev,
+						 "vbus-detect",
+						 GPIOD_ASIS);
+		err = PTR_ERR_OR_ZERO(nop->gpiod_vbus);
+	}
+
+	if (err)
+		return dev_err_probe(dev, err,
+				     "Error requesting RESET or VBUS GPIO\n");
+	if (nop->gpiod_reset)
+		gpiod_direction_output(nop->gpiod_reset, 1);
+
+	nop->phy.otg = devm_kzalloc(dev, sizeof(*nop->phy.otg),
+			GFP_KERNEL);
+	if (!nop->phy.otg)
+		return -ENOMEM;
+
+	nop->clk = devm_clk_get_optional(dev, "main_clk");
+	if (IS_ERR(nop->clk))
+		return dev_err_probe(dev, PTR_ERR(nop->clk),
+				     "Can't get phy clock\n");
+
+	if (clk_rate) {
+		err = clk_set_rate(nop->clk, clk_rate);
+		if (err)
+			return dev_err_probe(dev, err,
+					     "Error setting clock rate\n");
+	}
+
+	nop->vcc = devm_regulator_get_optional(dev, "vcc");
+	if (IS_ERR(nop->vcc) && PTR_ERR(nop->vcc) != -ENODEV)
+		return dev_err_probe(dev, PTR_ERR(nop->vcc),
+				     "could not get vcc regulator\n");
+
+	nop->vbus_draw = devm_regulator_get_exclusive(dev, "vbus");
+	if (PTR_ERR(nop->vbus_draw) == -ENODEV)
+		nop->vbus_draw = NULL;
+	if (IS_ERR(nop->vbus_draw))
+		return dev_err_probe(dev, PTR_ERR(nop->vbus_draw),
+				     "could not get vbus regulator\n");
+
+	nop->dev		= dev;
+	nop->phy.dev		= nop->dev;
+	nop->phy.label		= "nop-xceiv";
+	nop->phy.set_suspend	= nop_set_suspend;
+	nop->phy.type		= type;
+
+	nop->phy.otg->state		= OTG_STATE_UNDEFINED;
+	nop->phy.otg->usb_phy		= &nop->phy;
+	nop->phy.otg->set_host		= nop_set_host;
+	nop->phy.otg->set_peripheral	= nop_set_peripheral;
+	nop->phy.otg->set_vbus          = nop_set_vbus;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_phy_gen_create_phy);
+
+static int usb_phy_generic_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct usb_phy_generic	*nop;
+	int err;
+
+	nop = devm_kzalloc(dev, sizeof(*nop), GFP_KERNEL);
+	if (!nop)
+		return -ENOMEM;
+
+	err = usb_phy_gen_create_phy(dev, nop);
+	if (err)
+		return err;
+
+	if (nop->gpiod_vbus) {
+		err = devm_request_threaded_irq(dev,
+						gpiod_to_irq(nop->gpiod_vbus),
+						NULL, nop_gpio_vbus_thread,
+						VBUS_IRQ_FLAGS, "vbus_detect",
+						nop);
+		if (err)
+			return dev_err_probe(dev, err, "can't request irq %i\n",
+					     gpiod_to_irq(nop->gpiod_vbus));
+
+		nop->phy.otg->state = gpiod_get_value(nop->gpiod_vbus) ?
+			OTG_STATE_B_PERIPHERAL : OTG_STATE_B_IDLE;
+	}
+
+	nop->phy.init		= usb_gen_phy_init;
+	nop->phy.shutdown	= usb_gen_phy_shutdown;
+
+	err = usb_add_phy_dev(&nop->phy);
+	if (err)
+		return dev_err_probe(dev, err, "can't register transceiver\n");
+
+	platform_set_drvdata(pdev, nop);
+
+	device_set_wakeup_capable(dev,
+				  device_property_read_bool(dev, "wakeup-source"));
+
+	return 0;
+}
+
+static void usb_phy_generic_remove(struct platform_device *pdev)
+{
+	struct usb_phy_generic *nop = platform_get_drvdata(pdev);
+
+	usb_remove_phy(&nop->phy);
+
+	if (nop->vbus_draw && nop->vbus_draw_enabled)
+		regulator_disable(nop->vbus_draw);
+}
+
+static const struct of_device_id nop_xceiv_dt_ids[] = {
+	{ .compatible = "usb-nop-xceiv" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, nop_xceiv_dt_ids);
+
+static struct platform_driver usb_phy_generic_driver = {
+	.probe		= usb_phy_generic_probe,
+	.remove		= usb_phy_generic_remove,
+	.driver		= {
+		.name	= "usb_phy_generic",
+		.of_match_table = nop_xceiv_dt_ids,
+	},
+};
+
+static int __init usb_phy_generic_init(void)
+{
+	return platform_driver_register(&usb_phy_generic_driver);
+}
+subsys_initcall(usb_phy_generic_init);
+
+static void __exit usb_phy_generic_exit(void)
+{
+	platform_driver_unregister(&usb_phy_generic_driver);
+}
+module_exit(usb_phy_generic_exit);
+
+MODULE_ALIAS("platform:usb_phy_generic");
+MODULE_AUTHOR("Texas Instruments Inc");
+MODULE_DESCRIPTION("NOP USB Transceiver driver");
+MODULE_LICENSE("GPL");