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, 148 insertions, 0 deletions

diff --git a/drivers/hid/hid-ite.c b/drivers/hid/hid-ite.c
new file mode 100644
index 000000000..63908f24b
--- /dev/null
+++ b/drivers/hid/hid-ite.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HID driver for some ITE "special" devices
+ * Copyright (c) 2017 Hans de Goede <hdegoede@redhat.com>
+ */
+
+#include <linux/device.h>
+#include <linux/input.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define QUIRK_TOUCHPAD_ON_OFF_REPORT		BIT(0)
+
+static const __u8 *ite_report_fixup(struct hid_device *hdev, __u8 *rdesc, unsigned int *rsize)
+{
+
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
+
+	if (quirks & QUIRK_TOUCHPAD_ON_OFF_REPORT) {
+		/* For Acer Aspire Switch 10 SW5-012 keyboard-dock */
+		if (*rsize == 188 && rdesc[162] == 0x81 && rdesc[163] == 0x02) {
+			hid_info(hdev, "Fixing up Acer Sw5-012 ITE keyboard report descriptor\n");
+			rdesc[163] = HID_MAIN_ITEM_RELATIVE;
+		}
+		/* For Acer One S1002/S1003 keyboard-dock */
+		if (*rsize == 188 && rdesc[185] == 0x81 && rdesc[186] == 0x02) {
+			hid_info(hdev, "Fixing up Acer S1002/S1003 ITE keyboard report descriptor\n");
+			rdesc[186] = HID_MAIN_ITEM_RELATIVE;
+		}
+		/* For Acer Aspire Switch 10E (SW3-016) keyboard-dock */
+		if (*rsize == 210 && rdesc[184] == 0x81 && rdesc[185] == 0x02) {
+			hid_info(hdev, "Fixing up Acer Aspire Switch 10E (SW3-016) ITE keyboard report descriptor\n");
+			rdesc[185] = HID_MAIN_ITEM_RELATIVE;
+		}
+	}
+
+	return rdesc;
+}
+
+static int ite_input_mapping(struct hid_device *hdev,
+		struct hid_input *hi, struct hid_field *field,
+		struct hid_usage *usage, unsigned long **bit,
+		int *max)
+{
+
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
+
+	if ((quirks & QUIRK_TOUCHPAD_ON_OFF_REPORT) &&
+	    (usage->hid & HID_USAGE_PAGE) == 0x00880000) {
+		if (usage->hid == 0x00880078) {
+			/* Touchpad on, userspace expects F22 for this */
+			hid_map_usage_clear(hi, usage, bit, max, EV_KEY, KEY_F22);
+			return 1;
+		}
+		if (usage->hid == 0x00880079) {
+			/* Touchpad off, userspace expects F23 for this */
+			hid_map_usage_clear(hi, usage, bit, max, EV_KEY, KEY_F23);
+			return 1;
+		}
+		return -1;
+	}
+
+	return 0;
+}
+
+static int ite_event(struct hid_device *hdev, struct hid_field *field,
+		     struct hid_usage *usage, __s32 value)
+{
+	struct input_dev *input;
+
+	if (!(hdev->claimed & HID_CLAIMED_INPUT) || !field->hidinput)
+		return 0;
+
+	input = field->hidinput->input;
+
+	/*
+	 * The ITE8595 always reports 0 as value for the rfkill button. Luckily
+	 * it is the only button in its report, and it sends a report on
+	 * release only, so receiving a report means the button was pressed.
+	 */
+	if (usage->hid == HID_GD_RFKILL_BTN) {
+		input_event(input, EV_KEY, KEY_RFKILL, 1);
+		input_sync(input);
+		input_event(input, EV_KEY, KEY_RFKILL, 0);
+		input_sync(input);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int ite_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+
+	hid_set_drvdata(hdev, (void *)id);
+
+	ret = hid_open_report(hdev);
+	if (ret)
+		return ret;
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static const struct hid_device_id ite_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ITE, USB_DEVICE_ID_ITE8595) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_258A, USB_DEVICE_ID_258A_6A88) },
+	/* ITE8595 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_SWITCH5_012),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	/* ITE8910 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_ONE_S1002),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	/* ITE8910 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_ONE_S1003),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	/* ITE8910 USB kbd ctlr, with Synaptics touchpad connected to it. */
+	{ HID_DEVICE(BUS_USB, HID_GROUP_GENERIC,
+		     USB_VENDOR_ID_SYNAPTICS,
+		     USB_DEVICE_ID_SYNAPTICS_ACER_SWITCH5_017),
+	  .driver_data = QUIRK_TOUCHPAD_ON_OFF_REPORT },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, ite_devices);
+
+static struct hid_driver ite_driver = {
+	.name = "itetech",
+	.id_table = ite_devices,
+	.probe = ite_probe,
+	.report_fixup = ite_report_fixup,
+	.input_mapping = ite_input_mapping,
+	.event = ite_event,
+};
+module_hid_driver(ite_driver);
+
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_DESCRIPTION("HID driver for some ITE \"special\" devices");
+MODULE_LICENSE("GPL");