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, 159 insertions, 0 deletions

diff --git a/drivers/hid/hid-sjoy.c b/drivers/hid/hid-sjoy.c
new file mode 100644
index 000000000..193ab2a61
--- /dev/null
+++ b/drivers/hid/hid-sjoy.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Force feedback support for SmartJoy PLUS PS2->USB adapter
+ *
+ *  Copyright (c) 2009 Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
+ *
+ *  Based of hid-pl.c and hid-gaff.c
+ *   Copyright (c) 2007, 2009 Anssi Hannula <anssi.hannula@gmail.com>
+ *   Copyright (c) 2008 Lukasz Lubojanski <lukasz@lubojanski.info>
+ */
+
+/*
+ */
+
+/* #define DEBUG */
+
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+#include "hid-ids.h"
+
+#ifdef CONFIG_SMARTJOYPLUS_FF
+
+struct sjoyff_device {
+	struct hid_report *report;
+};
+
+static int hid_sjoyff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct sjoyff_device *sjoyff = data;
+	u32 left, right;
+
+	left = effect->u.rumble.strong_magnitude;
+	right = effect->u.rumble.weak_magnitude;
+	dev_dbg(&dev->dev, "called with 0x%08x 0x%08x\n", left, right);
+
+	left = left * 0xff / 0xffff;
+	right = (right != 0); /* on/off only */
+
+	sjoyff->report->field[0]->value[1] = right;
+	sjoyff->report->field[0]->value[2] = left;
+	dev_dbg(&dev->dev, "running with 0x%02x 0x%02x\n", left, right);
+	hid_hw_request(hid, sjoyff->report, HID_REQ_SET_REPORT);
+
+	return 0;
+}
+
+static int sjoy_input_configured(struct hid_device *hid, struct hid_input *hidinput)
+{
+	struct sjoyff_device *sjoyff;
+	struct hid_report *report;
+	struct list_head *report_list =
+			&hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	struct input_dev *dev = hidinput->input;
+	int error;
+
+	if (!list_is_first(&hidinput->list, &hid->inputs))
+		return 0;
+
+	report = list_first_entry_or_null(report_list, struct hid_report, list);
+	if (!report) {
+		hid_err(hid, "no output reports found\n");
+		return -ENODEV;
+	}
+	if (report->maxfield < 1) {
+		hid_err(hid, "no fields in the report\n");
+		return -ENODEV;
+	}
+
+	if (report->field[0]->report_count < 3) {
+		hid_err(hid, "not enough values in the field\n");
+		return -ENODEV;
+	}
+
+	sjoyff = kzalloc_obj(struct sjoyff_device);
+	if (!sjoyff)
+		return -ENOMEM;
+
+	set_bit(FF_RUMBLE, dev->ffbit);
+
+	sjoyff->report = report;
+	sjoyff->report->field[0]->value[0] = 0x01;
+	sjoyff->report->field[0]->value[1] = 0x00;
+	sjoyff->report->field[0]->value[2] = 0x00;
+	hid_hw_request(hid, sjoyff->report, HID_REQ_SET_REPORT);
+
+	error = input_ff_create_memless(dev, sjoyff, hid_sjoyff_play);
+	if (error) {
+		kfree(sjoyff);
+		return error;
+	}
+
+	return 0;
+}
+#else
+static inline int sjoy_input_configured(struct hid_device *hid,
+					struct hid_input *hidinput)
+{
+	return 0;
+}
+#endif
+
+static int sjoy_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+
+	hdev->quirks |= id->driver_data;
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		return ret;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id sjoy_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_WISEGROUP_LTD, USB_DEVICE_ID_SUPER_JOY_BOX_3_PRO),
+		.driver_data = HID_QUIRK_NOGET },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_WISEGROUP_LTD, USB_DEVICE_ID_SUPER_DUAL_BOX_PRO),
+		.driver_data = HID_QUIRK_MULTI_INPUT | HID_QUIRK_NOGET |
+			       HID_QUIRK_SKIP_OUTPUT_REPORTS },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_WISEGROUP_LTD, USB_DEVICE_ID_SUPER_JOY_BOX_5_PRO),
+		.driver_data = HID_QUIRK_MULTI_INPUT | HID_QUIRK_NOGET |
+			       HID_QUIRK_SKIP_OUTPUT_REPORTS },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_WISEGROUP, USB_DEVICE_ID_SMARTJOY_PLUS) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_WISEGROUP, USB_DEVICE_ID_SUPER_JOY_BOX_3) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_WISEGROUP, USB_DEVICE_ID_DUAL_USB_JOYPAD),
+		.driver_data = HID_QUIRK_MULTI_INPUT |
+			       HID_QUIRK_SKIP_OUTPUT_REPORTS },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_PLAYDOTCOM, USB_DEVICE_ID_PLAYDOTCOM_EMS_USBII),
+		.driver_data = HID_QUIRK_MULTI_INPUT |
+			       HID_QUIRK_SKIP_OUTPUT_REPORTS },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, sjoy_devices);
+
+static struct hid_driver sjoy_driver = {
+	.name = "smartjoyplus",
+	.id_table = sjoy_devices,
+	.probe = sjoy_probe,
+	.input_configured = sjoy_input_configured,
+};
+module_hid_driver(sjoy_driver);
+
+MODULE_DESCRIPTION("Force feedback support for SmartJoy PLUS PS2->USB adapter");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jussi Kivilinna");
+