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, 266 insertions, 0 deletions

diff --git a/drivers/bluetooth/bcm203x.c b/drivers/bluetooth/bcm203x.c
new file mode 100644
index 000000000..c738ad040
--- /dev/null
+++ b/drivers/bluetooth/bcm203x.c
@@ -0,0 +1,266 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *  Broadcom Blutonium firmware driver
+ *
+ *  Copyright (C) 2003  Maxim Krasnyansky <maxk@qualcomm.com>
+ *  Copyright (C) 2003  Marcel Holtmann <marcel@holtmann.org>
+ */
+
+#include <linux/module.h>
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+
+#include <linux/device.h>
+#include <linux/firmware.h>
+
+#include <linux/usb.h>
+
+#include <net/bluetooth/bluetooth.h>
+
+#define VERSION "1.2"
+
+static const struct usb_device_id bcm203x_table[] = {
+	/* Broadcom Blutonium (BCM2033) */
+	{ USB_DEVICE(0x0a5c, 0x2033) },
+
+	{ }	/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(usb, bcm203x_table);
+
+#define BCM203X_ERROR		0
+#define BCM203X_RESET		1
+#define BCM203X_LOAD_MINIDRV	2
+#define BCM203X_SELECT_MEMORY	3
+#define BCM203X_CHECK_MEMORY	4
+#define BCM203X_LOAD_FIRMWARE	5
+#define BCM203X_CHECK_FIRMWARE	6
+
+#define BCM203X_IN_EP		0x81
+#define BCM203X_OUT_EP		0x02
+
+struct bcm203x_data {
+	struct usb_device	*udev;
+
+	unsigned long		state;
+
+	struct work_struct	work;
+	atomic_t		shutdown;
+
+	struct urb		*urb;
+	unsigned char		*buffer;
+
+	unsigned char		*fw_data;
+	unsigned int		fw_size;
+	unsigned int		fw_sent;
+};
+
+static void bcm203x_complete(struct urb *urb)
+{
+	struct bcm203x_data *data = urb->context;
+	struct usb_device *udev = urb->dev;
+	int len;
+
+	BT_DBG("udev %p urb %p", udev, urb);
+
+	if (urb->status) {
+		BT_ERR("URB failed with status %d", urb->status);
+		data->state = BCM203X_ERROR;
+		return;
+	}
+
+	switch (data->state) {
+	case BCM203X_LOAD_MINIDRV:
+		memcpy(data->buffer, "#", 1);
+
+		usb_fill_bulk_urb(urb, udev, usb_sndbulkpipe(udev, BCM203X_OUT_EP),
+				data->buffer, 1, bcm203x_complete, data);
+
+		data->state = BCM203X_SELECT_MEMORY;
+
+		/* use workqueue to have a small delay */
+		schedule_work(&data->work);
+		break;
+
+	case BCM203X_SELECT_MEMORY:
+		usb_fill_int_urb(urb, udev, usb_rcvintpipe(udev, BCM203X_IN_EP),
+				data->buffer, 32, bcm203x_complete, data, 1);
+
+		data->state = BCM203X_CHECK_MEMORY;
+
+		if (usb_submit_urb(data->urb, GFP_ATOMIC) < 0)
+			BT_ERR("Can't submit URB");
+		break;
+
+	case BCM203X_CHECK_MEMORY:
+		if (data->buffer[0] != '#') {
+			BT_ERR("Memory select failed");
+			data->state = BCM203X_ERROR;
+			break;
+		}
+
+		data->state = BCM203X_LOAD_FIRMWARE;
+		fallthrough;
+	case BCM203X_LOAD_FIRMWARE:
+		if (data->fw_sent == data->fw_size) {
+			usb_fill_int_urb(urb, udev, usb_rcvintpipe(udev, BCM203X_IN_EP),
+				data->buffer, 32, bcm203x_complete, data, 1);
+
+			data->state = BCM203X_CHECK_FIRMWARE;
+		} else {
+			len = min_t(uint, data->fw_size - data->fw_sent, 4096);
+
+			usb_fill_bulk_urb(urb, udev, usb_sndbulkpipe(udev, BCM203X_OUT_EP),
+				data->fw_data + data->fw_sent, len, bcm203x_complete, data);
+
+			data->fw_sent += len;
+		}
+
+		if (usb_submit_urb(data->urb, GFP_ATOMIC) < 0)
+			BT_ERR("Can't submit URB");
+		break;
+
+	case BCM203X_CHECK_FIRMWARE:
+		if (data->buffer[0] != '.') {
+			BT_ERR("Firmware loading failed");
+			data->state = BCM203X_ERROR;
+			break;
+		}
+
+		data->state = BCM203X_RESET;
+		break;
+	}
+}
+
+static void bcm203x_work(struct work_struct *work)
+{
+	struct bcm203x_data *data =
+		container_of(work, struct bcm203x_data, work);
+
+	if (atomic_read(&data->shutdown))
+		return;
+
+	if (usb_submit_urb(data->urb, GFP_KERNEL) < 0)
+		BT_ERR("Can't submit URB");
+}
+
+static int bcm203x_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	const struct firmware *firmware;
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct bcm203x_data *data;
+	int size;
+
+	BT_DBG("intf %p id %p", intf, id);
+
+	if (intf->cur_altsetting->desc.bInterfaceNumber != 0)
+		return -ENODEV;
+
+	data = devm_kzalloc(&intf->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->udev  = udev;
+	data->state = BCM203X_LOAD_MINIDRV;
+
+	data->urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!data->urb)
+		return -ENOMEM;
+
+	if (request_firmware(&firmware, "BCM2033-MD.hex", &udev->dev) < 0) {
+		BT_ERR("Mini driver request failed");
+		usb_free_urb(data->urb);
+		return -EIO;
+	}
+
+	BT_DBG("minidrv data %p size %zu", firmware->data, firmware->size);
+
+	size = max_t(uint, firmware->size, 4096);
+
+	data->buffer = kmalloc(size, GFP_KERNEL);
+	if (!data->buffer) {
+		BT_ERR("Can't allocate memory for mini driver");
+		release_firmware(firmware);
+		usb_free_urb(data->urb);
+		return -ENOMEM;
+	}
+
+	memcpy(data->buffer, firmware->data, firmware->size);
+
+	usb_fill_bulk_urb(data->urb, udev, usb_sndbulkpipe(udev, BCM203X_OUT_EP),
+			data->buffer, firmware->size, bcm203x_complete, data);
+
+	release_firmware(firmware);
+
+	if (request_firmware(&firmware, "BCM2033-FW.bin", &udev->dev) < 0) {
+		BT_ERR("Firmware request failed");
+		usb_free_urb(data->urb);
+		kfree(data->buffer);
+		return -EIO;
+	}
+
+	BT_DBG("firmware data %p size %zu", firmware->data, firmware->size);
+
+	data->fw_data = kmemdup(firmware->data, firmware->size, GFP_KERNEL);
+	if (!data->fw_data) {
+		BT_ERR("Can't allocate memory for firmware image");
+		release_firmware(firmware);
+		usb_free_urb(data->urb);
+		kfree(data->buffer);
+		return -ENOMEM;
+	}
+
+	data->fw_size = firmware->size;
+	data->fw_sent = 0;
+
+	release_firmware(firmware);
+
+	INIT_WORK(&data->work, bcm203x_work);
+
+	usb_set_intfdata(intf, data);
+
+	/* use workqueue to have a small delay */
+	schedule_work(&data->work);
+
+	return 0;
+}
+
+static void bcm203x_disconnect(struct usb_interface *intf)
+{
+	struct bcm203x_data *data = usb_get_intfdata(intf);
+
+	BT_DBG("intf %p", intf);
+
+	atomic_inc(&data->shutdown);
+	cancel_work_sync(&data->work);
+
+	usb_kill_urb(data->urb);
+
+	usb_set_intfdata(intf, NULL);
+
+	usb_free_urb(data->urb);
+	kfree(data->fw_data);
+	kfree(data->buffer);
+}
+
+static struct usb_driver bcm203x_driver = {
+	.name		= "bcm203x",
+	.probe		= bcm203x_probe,
+	.disconnect	= bcm203x_disconnect,
+	.id_table	= bcm203x_table,
+	.disable_hub_initiated_lpm = 1,
+};
+
+module_usb_driver(bcm203x_driver);
+
+MODULE_AUTHOR("Marcel Holtmann <marcel@holtmann.org>");
+MODULE_DESCRIPTION("Broadcom Blutonium firmware driver ver " VERSION);
+MODULE_VERSION(VERSION);
+MODULE_LICENSE("GPL");
+MODULE_FIRMWARE("BCM2033-MD.hex");
+MODULE_FIRMWARE("BCM2033-FW.bin");