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, 369 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib-devres.c b/drivers/gpio/gpiolib-devres.c
new file mode 100644
index 000000000..2ec825ffa
--- /dev/null
+++ b/drivers/gpio/gpiolib-devres.c
@@ -0,0 +1,369 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * devres.c - managed gpio resources
+ * This file is based on kernel/irq/devres.c
+ *
+ * Copyright (c) 2011 John Crispin <john@phrozen.org>
+ */
+
+#include <linux/device/devres.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/gfp.h>
+#include <linux/types.h>
+
+#include <linux/gpio/consumer.h>
+
+#include "gpiolib.h"
+
+struct fwnode_handle;
+struct lock_class_key;
+
+static void devm_gpiod_release(void *desc)
+{
+	gpiod_put(desc);
+}
+
+static void devm_gpiod_release_array(void *descs)
+{
+	gpiod_put_array(descs);
+}
+
+/**
+ * devm_gpiod_get - Resource-managed gpiod_get()
+ * @dev:	GPIO consumer
+ * @con_id:	function within the GPIO consumer
+ * @flags:	optional GPIO initialization flags
+ *
+ * Managed gpiod_get(). GPIO descriptors returned from this function are
+ * automatically disposed on driver detach. See gpiod_get() for detailed
+ * information about behavior and return values.
+ *
+ * Returns:
+ * The GPIO descriptor corresponding to the function @con_id of device
+ * dev, %-ENOENT if no GPIO has been assigned to the requested function, or
+ * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
+ */
+struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
+					      const char *con_id,
+					      enum gpiod_flags flags)
+{
+	return devm_gpiod_get_index(dev, con_id, 0, flags);
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_get);
+
+/**
+ * devm_gpiod_get_optional - Resource-managed gpiod_get_optional()
+ * @dev: GPIO consumer
+ * @con_id: function within the GPIO consumer
+ * @flags: optional GPIO initialization flags
+ *
+ * Managed gpiod_get_optional(). GPIO descriptors returned from this function
+ * are automatically disposed on driver detach. See gpiod_get_optional() for
+ * detailed information about behavior and return values.
+ *
+ * Returns:
+ * The GPIO descriptor corresponding to the function @con_id of device
+ * dev, NULL if no GPIO has been assigned to the requested function, or
+ * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
+ */
+struct gpio_desc *__must_check devm_gpiod_get_optional(struct device *dev,
+						       const char *con_id,
+						       enum gpiod_flags flags)
+{
+	return devm_gpiod_get_index_optional(dev, con_id, 0, flags);
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_get_optional);
+
+/**
+ * devm_gpiod_get_index - Resource-managed gpiod_get_index()
+ * @dev:	GPIO consumer
+ * @con_id:	function within the GPIO consumer
+ * @idx:	index of the GPIO to obtain in the consumer
+ * @flags:	optional GPIO initialization flags
+ *
+ * Managed gpiod_get_index(). GPIO descriptors returned from this function are
+ * automatically disposed on driver detach. See gpiod_get_index() for detailed
+ * information about behavior and return values.
+ *
+ * Returns:
+ * The GPIO descriptor corresponding to the function @con_id of device
+ * dev, %-ENOENT if no GPIO has been assigned to the requested function, or
+ * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
+ */
+struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
+						    const char *con_id,
+						    unsigned int idx,
+						    enum gpiod_flags flags)
+{
+	struct gpio_desc *desc;
+	int ret;
+
+	desc = gpiod_get_index(dev, con_id, idx, flags);
+	if (IS_ERR(desc))
+		return desc;
+
+	/*
+	 * For non-exclusive GPIO descriptors, check if this descriptor is
+	 * already under resource management by this device.
+	 */
+	if (flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE) {
+		bool dres;
+
+		dres = devm_is_action_added(dev, devm_gpiod_release, desc);
+		if (dres)
+			return desc;
+	}
+
+	ret = devm_add_action_or_reset(dev, devm_gpiod_release, desc);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return desc;
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_get_index);
+
+/**
+ * devm_fwnode_gpiod_get_index - get a GPIO descriptor from a given node
+ * @dev:	GPIO consumer
+ * @fwnode:	firmware node containing GPIO reference
+ * @con_id:	function within the GPIO consumer
+ * @index:	index of the GPIO to obtain in the consumer
+ * @flags:	GPIO initialization flags
+ * @label:	label to attach to the requested GPIO
+ *
+ * GPIO descriptors returned from this function are automatically disposed on
+ * driver detach.
+ *
+ * Returns:
+ * The GPIO descriptor corresponding to the function @con_id of device
+ * dev, %-ENOENT if no GPIO has been assigned to the requested function, or
+ * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
+ */
+struct gpio_desc *devm_fwnode_gpiod_get_index(struct device *dev,
+					      struct fwnode_handle *fwnode,
+					      const char *con_id, int index,
+					      enum gpiod_flags flags,
+					      const char *label)
+{
+	struct gpio_desc *desc;
+	int ret;
+
+	desc = gpiod_find_and_request(dev, fwnode, con_id, index, flags, label, false);
+	if (IS_ERR(desc))
+		return desc;
+
+	ret = devm_add_action_or_reset(dev, devm_gpiod_release, desc);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return desc;
+}
+EXPORT_SYMBOL_GPL(devm_fwnode_gpiod_get_index);
+
+/**
+ * devm_gpiod_get_index_optional - Resource-managed gpiod_get_index_optional()
+ * @dev: GPIO consumer
+ * @con_id: function within the GPIO consumer
+ * @index: index of the GPIO to obtain in the consumer
+ * @flags: optional GPIO initialization flags
+ *
+ * Managed gpiod_get_index_optional(). GPIO descriptors returned from this
+ * function are automatically disposed on driver detach. See
+ * gpiod_get_index_optional() for detailed information about behavior and
+ * return values.
+ *
+ * Returns:
+ * The GPIO descriptor corresponding to the function @con_id of device
+ * dev, %NULL if no GPIO has been assigned to the requested function, or
+ * another IS_ERR() code if an error occurred while trying to acquire the GPIO.
+ */
+struct gpio_desc *__must_check devm_gpiod_get_index_optional(struct device *dev,
+							     const char *con_id,
+							     unsigned int index,
+							     enum gpiod_flags flags)
+{
+	struct gpio_desc *desc;
+
+	desc = devm_gpiod_get_index(dev, con_id, index, flags);
+	if (gpiod_not_found(desc))
+		return NULL;
+
+	return desc;
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_get_index_optional);
+
+/**
+ * devm_gpiod_get_array - Resource-managed gpiod_get_array()
+ * @dev:	GPIO consumer
+ * @con_id:	function within the GPIO consumer
+ * @flags:	optional GPIO initialization flags
+ *
+ * Managed gpiod_get_array(). GPIO descriptors returned from this function are
+ * automatically disposed on driver detach. See gpiod_get_array() for detailed
+ * information about behavior and return values.
+ *
+ * Returns:
+ * The GPIO descriptors corresponding to the function @con_id of device
+ * dev, %-ENOENT if no GPIO has been assigned to the requested function,
+ * or another IS_ERR() code if an error occurred while trying to acquire
+ * the GPIOs.
+ */
+struct gpio_descs *__must_check devm_gpiod_get_array(struct device *dev,
+						     const char *con_id,
+						     enum gpiod_flags flags)
+{
+	struct gpio_descs *descs;
+	int ret;
+
+	descs = gpiod_get_array(dev, con_id, flags);
+	if (IS_ERR(descs))
+		return descs;
+
+	ret = devm_add_action_or_reset(dev, devm_gpiod_release_array, descs);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return descs;
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_get_array);
+
+/**
+ * devm_gpiod_get_array_optional - Resource-managed gpiod_get_array_optional()
+ * @dev:	GPIO consumer
+ * @con_id:	function within the GPIO consumer
+ * @flags:	optional GPIO initialization flags
+ *
+ * Managed gpiod_get_array_optional(). GPIO descriptors returned from this
+ * function are automatically disposed on driver detach.
+ * See gpiod_get_array_optional() for detailed information about behavior and
+ * return values.
+ *
+ * Returns:
+ * The GPIO descriptors corresponding to the function @con_id of device
+ * dev, %NULL if no GPIO has been assigned to the requested function,
+ * or another IS_ERR() code if an error occurred while trying to acquire
+ * the GPIOs.
+ */
+struct gpio_descs *__must_check
+devm_gpiod_get_array_optional(struct device *dev, const char *con_id,
+			      enum gpiod_flags flags)
+{
+	struct gpio_descs *descs;
+
+	descs = devm_gpiod_get_array(dev, con_id, flags);
+	if (gpiod_not_found(descs))
+		return NULL;
+
+	return descs;
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_get_array_optional);
+
+/**
+ * devm_gpiod_put - Resource-managed gpiod_put()
+ * @dev:	GPIO consumer
+ * @desc:	GPIO descriptor to dispose of
+ *
+ * Dispose of a GPIO descriptor obtained with devm_gpiod_get() or
+ * devm_gpiod_get_index(). Normally this function will not be called as the GPIO
+ * will be disposed of by the resource management code.
+ */
+void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
+{
+	devm_release_action(dev, devm_gpiod_release, desc);
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_put);
+
+/**
+ * devm_gpiod_unhinge - Remove resource management from a gpio descriptor
+ * @dev:	GPIO consumer
+ * @desc:	GPIO descriptor to remove resource management from
+ *
+ * *DEPRECATED*
+ * This function should not be used. It's been provided as a workaround for
+ * resource ownership issues in the regulator framework and should be replaced
+ * with a better solution.
+ *
+ * Remove resource management from a GPIO descriptor. This is needed when
+ * you want to hand over lifecycle management of a descriptor to another
+ * mechanism.
+ */
+void devm_gpiod_unhinge(struct device *dev, struct gpio_desc *desc)
+{
+	int ret;
+
+	if (IS_ERR_OR_NULL(desc))
+		return;
+
+	/*
+	 * If the GPIO descriptor is requested as nonexclusive, we
+	 * may call this function several times on the same descriptor
+	 * so it is OK if devres_destroy() returns -ENOENT.
+	 */
+	ret = devm_remove_action_nowarn(dev, devm_gpiod_release, desc);
+	if (ret == -ENOENT)
+		return;
+	/* Anything else we should warn about */
+	WARN_ON(ret);
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_unhinge);
+
+/**
+ * devm_gpiod_put_array - Resource-managed gpiod_put_array()
+ * @dev:	GPIO consumer
+ * @descs:	GPIO descriptor array to dispose of
+ *
+ * Dispose of an array of GPIO descriptors obtained with devm_gpiod_get_array().
+ * Normally this function will not be called as the GPIOs will be disposed of
+ * by the resource management code.
+ */
+void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs)
+{
+	devm_release_action(dev, devm_gpiod_release_array, descs);
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_put_array);
+
+static void devm_gpio_chip_release(void *data)
+{
+	struct gpio_chip *gc = data;
+
+	gpiochip_remove(gc);
+}
+
+/**
+ * devm_gpiochip_add_data_with_key() - Resource managed gpiochip_add_data_with_key()
+ * @dev: pointer to the device that gpio_chip belongs to.
+ * @gc: the GPIO chip to register
+ * @data: driver-private data associated with this chip
+ * @lock_key: lockdep class for IRQ lock
+ * @request_key: lockdep class for IRQ request
+ *
+ * Context: potentially before irqs will work
+ *
+ * The gpio chip automatically be released when the device is unbound.
+ *
+ * Returns:
+ * A negative errno if the chip can't be registered, such as because the
+ * gc->base is invalid or already associated with a different chip.
+ * Otherwise it returns zero as a success code.
+ */
+int devm_gpiochip_add_data_with_key(struct device *dev, struct gpio_chip *gc, void *data,
+				    struct lock_class_key *lock_key,
+				    struct lock_class_key *request_key)
+{
+	int ret;
+
+	/*
+	 * We are passing the devres device here so if the user did not pass
+	 * another parent, it's this one.
+	 */
+	if (!gc->parent)
+		gc->parent = dev;
+
+	ret = gpiochip_add_data_with_key(gc, data, lock_key, request_key);
+	if (ret < 0)
+		return ret;
+
+	return devm_add_action_or_reset(dev, devm_gpio_chip_release, gc);
+}
+EXPORT_SYMBOL_GPL(devm_gpiochip_add_data_with_key);