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, 206 insertions, 0 deletions

diff --git a/drivers/hid/hid-universal-pidff.c b/drivers/hid/hid-universal-pidff.c
new file mode 100644
index 000000000..60180467a
--- /dev/null
+++ b/drivers/hid/hid-universal-pidff.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID UNIVERSAL PIDFF
+ * hid-pidff wrapper for PID-enabled devices
+ * Handles device reports, quirks and extends usable button range
+ *
+ * Copyright (c) 2024, 2025 Oleg Makarenko
+ * Copyright (c) 2024, 2025 Tomasz Pakuła
+ */
+
+#include "hid-ids.h"
+#include "usbhid/hid-pidff.h"
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/input-event-codes.h>
+#include <linux/module.h>
+
+#define JOY_RANGE (BTN_DEAD - BTN_JOYSTICK + 1)
+
+/*
+ * Map buttons manually to extend the default joystick button limit
+ */
+static int universal_pidff_input_mapping(struct hid_device *hdev,
+					 struct hid_input *hi,
+					 struct hid_field *field,
+					 struct hid_usage *usage,
+					 unsigned long **bit, int *max)
+{
+	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_BUTTON)
+		return 0;
+
+	if (field->application != HID_GD_JOYSTICK)
+		return 0;
+
+	int button = ((usage->hid - 1) & HID_USAGE);
+	int code = button + BTN_JOYSTICK;
+
+	/* Detect the end of JOYSTICK buttons range */
+	if (code > BTN_DEAD)
+		code = button + KEY_NEXT_FAVORITE - JOY_RANGE;
+
+	/*
+	 * Map overflowing buttons to KEY_RESERVED to not ignore
+	 * them and let them still trigger MSC_SCAN
+	 */
+	if (code > KEY_MAX)
+		code = KEY_RESERVED;
+
+	hid_map_usage(hi, usage, bit, max, EV_KEY, code);
+	hid_dbg(hdev, "Button %d: usage %d", button, code);
+	return 1;
+}
+
+/*
+ * Check if the device is PID and initialize it
+ * Add quirks after initialisation
+ */
+static int universal_pidff_probe(struct hid_device *hdev,
+				 const struct hid_device_id *id)
+{
+	int i, error;
+
+	error = hid_parse(hdev);
+	if (error) {
+		hid_err(hdev, "HID parse failed\n");
+		goto err;
+	}
+
+	error = hid_hw_start(hdev, HID_CONNECT_DEFAULT & ~HID_CONNECT_FF);
+	if (error) {
+		hid_err(hdev, "HID hw start failed\n");
+		goto err;
+	}
+
+	/* Check if device contains PID usage page */
+	error = 1;
+	for (i = 0; i < hdev->collection_size; i++)
+		if ((hdev->collection[i].usage & HID_USAGE_PAGE) == HID_UP_PID) {
+			error = 0;
+			hid_dbg(hdev, "PID usage page found\n");
+			break;
+		}
+
+	/*
+	 * Do not fail as this might be the second "device"
+	 * just for additional buttons/axes. Exit cleanly if force
+	 * feedback usage page wasn't found (included devices were
+	 * tested and confirmed to be USB PID after all).
+	 */
+	if (error) {
+		hid_dbg(hdev, "PID usage page not found in the descriptor\n");
+		return 0;
+	}
+
+	/* Check if HID_PID support is enabled */
+	int (*init_function)(struct hid_device *, u32);
+
+	init_function = hid_pidff_init_with_quirks;
+	if (!init_function) {
+		hid_warn(hdev, "HID_PID support not enabled!\n");
+		return 0;
+	}
+
+	error = init_function(hdev, id->driver_data);
+	if (error) {
+		hid_warn(hdev, "Error initialising force feedback\n");
+		goto err_stop;
+	}
+
+	hid_info(hdev, "Universal pidff driver loaded successfully!");
+
+	return 0;
+err_stop:
+	hid_hw_stop(hdev);
+err:
+	return error;
+}
+
+static int universal_pidff_input_configured(struct hid_device *hdev,
+					    struct hid_input *hidinput)
+{
+	int axis;
+	struct input_dev *input = hidinput->input;
+
+	if (!input->absinfo)
+		return 0;
+
+	/* Decrease fuzz and deadzone on available axes */
+	for (axis = ABS_X; axis <= ABS_BRAKE; axis++) {
+		if (!test_bit(axis, input->absbit))
+			continue;
+
+		input_set_abs_params(input, axis, input->absinfo[axis].minimum,
+				     input->absinfo[axis].maximum,
+				     axis == ABS_X ? 0 : 8, 0);
+	}
+
+	/* Remove fuzz and deadzone from the second joystick axis */
+	if (hdev->vendor == USB_VENDOR_ID_FFBEAST &&
+	    hdev->product == USB_DEVICE_ID_FFBEAST_JOYSTICK)
+		input_set_abs_params(input, ABS_Y,
+				     input->absinfo[ABS_Y].minimum,
+				     input->absinfo[ABS_Y].maximum, 0, 0);
+
+	return 0;
+}
+
+static const struct hid_device_id universal_pidff_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R3),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R3_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R5),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R5_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R9),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R9_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R12),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R12_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R16_R21),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MOZA, USB_DEVICE_ID_MOZA_R16_R21_2),
+	  .driver_data = HID_PIDFF_QUIRK_FIX_CONDITIONAL_DIRECTION },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_CAMMUS, USB_DEVICE_ID_CAMMUS_C5) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_CAMMUS, USB_DEVICE_ID_CAMMUS_C12) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_VRS, USB_DEVICE_ID_VRS_DFP),
+	  .driver_data = HID_PIDFF_QUIRK_PERMISSIVE_CONTROL },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FFBEAST, USB_DEVICE_ID_FFBEAST_JOYSTICK), },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FFBEAST, USB_DEVICE_ID_FFBEAST_RUDDER), },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FFBEAST, USB_DEVICE_ID_FFBEAST_WHEEL) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V10),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V12),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V12_LITE),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_PXN_V12_LITE_2),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LITE_STAR, USB_DEVICE_ID_LITE_STAR_GT987),
+	  .driver_data = HID_PIDFF_QUIRK_PERIODIC_SINE_ONLY },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_INVICTA) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_FORTE) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_LA_PRIMA) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ASETEK, USB_DEVICE_ID_ASETEK_TONY_KANAAN) },
+	{}
+};
+MODULE_DEVICE_TABLE(hid, universal_pidff_devices);
+
+static struct hid_driver universal_pidff = {
+	.name = "hid-universal-pidff",
+	.id_table = universal_pidff_devices,
+	.input_mapping = universal_pidff_input_mapping,
+	.probe = universal_pidff_probe,
+	.input_configured = universal_pidff_input_configured
+};
+module_hid_driver(universal_pidff);
+
+MODULE_DESCRIPTION("Universal driver for USB PID Force Feedback devices");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Oleg Makarenko <oleg@makarenk.ooo>");
+MODULE_AUTHOR("Tomasz Pakuła <tomasz.pakula.oficjalny@gmail.com>");