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, 126 insertions, 0 deletions

diff --git a/drivers/hid/hid-razer.c b/drivers/hid/hid-razer.c
new file mode 100644
index 000000000..7f48258c6
--- /dev/null
+++ b/drivers/hid/hid-razer.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  HID driver for gaming keys on Razer Blackwidow gaming keyboards
+ *  Macro Key Keycodes: M1 = 191, M2 = 192, M3 = 193, M4 = 194, M5 = 195
+ *
+ *  Copyright (c) 2021 Jelle van der Waa <jvanderwaa@redhat.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/usb.h>
+#include <linux/wait.h>
+
+#include "hid-ids.h"
+
+#define map_key_clear(c) hid_map_usage_clear(hi, usage, bit, max, EV_KEY, (c))
+
+#define RAZER_BLACKWIDOW_TRANSFER_BUF_SIZE	91
+
+static bool macro_key_remapping = 1;
+module_param(macro_key_remapping, bool, 0644);
+MODULE_PARM_DESC(macro_key_remapping, " on (Y) off (N)");
+
+
+static unsigned char blackwidow_init[RAZER_BLACKWIDOW_TRANSFER_BUF_SIZE] = {
+	0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x04,
+	0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x04, 0x00
+};
+
+static int razer_input_mapping(struct hid_device *hdev,
+		struct hid_input *hi, struct hid_field *field,
+		struct hid_usage *usage, unsigned long **bit, int *max)
+{
+
+	if (!macro_key_remapping)
+		return 0;
+
+	if ((usage->hid & HID_UP_KEYBOARD) != HID_UP_KEYBOARD)
+		return 0;
+
+	switch (usage->hid & ~HID_UP_KEYBOARD) {
+	case 0x68:
+		map_key_clear(KEY_MACRO1);
+		return 1;
+	case 0x69:
+		map_key_clear(KEY_MACRO2);
+		return 1;
+	case 0x6a:
+		map_key_clear(KEY_MACRO3);
+		return 1;
+	case 0x6b:
+		map_key_clear(KEY_MACRO4);
+		return 1;
+	case 0x6c:
+		map_key_clear(KEY_MACRO5);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int razer_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	char *buf;
+	int ret = 0;
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	/*
+	 * Only send the enable macro keys command for the third device
+	 * identified as mouse input.
+	 */
+	if (hdev->type == HID_TYPE_USBMOUSE) {
+		buf = kmemdup(blackwidow_init, RAZER_BLACKWIDOW_TRANSFER_BUF_SIZE, GFP_KERNEL);
+		if (buf == NULL)
+			return -ENOMEM;
+
+		ret = hid_hw_raw_request(hdev, 0, buf, RAZER_BLACKWIDOW_TRANSFER_BUF_SIZE,
+				HID_FEATURE_REPORT, HID_REQ_SET_REPORT);
+		if (ret != RAZER_BLACKWIDOW_TRANSFER_BUF_SIZE)
+			hid_err(hdev, "failed to enable macro keys: %d\n", ret);
+
+		kfree(buf);
+	}
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static const struct hid_device_id razer_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_RAZER,
+		USB_DEVICE_ID_RAZER_BLACKWIDOW) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_RAZER,
+		USB_DEVICE_ID_RAZER_BLACKWIDOW_CLASSIC) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_RAZER,
+		USB_DEVICE_ID_RAZER_BLACKWIDOW_ULTIMATE) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, razer_devices);
+
+static struct hid_driver razer_driver = {
+	.name = "razer",
+	.id_table = razer_devices,
+	.input_mapping = razer_input_mapping,
+	.probe = razer_probe,
+};
+module_hid_driver(razer_driver);
+
+MODULE_AUTHOR("Jelle van der Waa <jvanderwaa@redhat.com>");
+MODULE_DESCRIPTION("HID driver for gaming keys on Razer Blackwidow gaming keyboards");
+MODULE_LICENSE("GPL");