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, 218 insertions, 0 deletions

diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
new file mode 100644
index 000000000..48ac7ca93
--- /dev/null
+++ b/drivers/bluetooth/hci_uart.h
@@ -0,0 +1,218 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *
+ *  Bluetooth HCI UART driver
+ *
+ *  Copyright (C) 2000-2001  Qualcomm Incorporated
+ *  Copyright (C) 2002-2003  Maxim Krasnyansky <maxk@qualcomm.com>
+ *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
+ */
+
+#ifndef N_HCI
+#define N_HCI	15
+#endif
+
+/* Ioctls */
+#define HCIUARTSETPROTO		_IOW('U', 200, int)
+#define HCIUARTGETPROTO		_IOR('U', 201, int)
+#define HCIUARTGETDEVICE	_IOR('U', 202, int)
+#define HCIUARTSETFLAGS		_IOW('U', 203, int)
+#define HCIUARTGETFLAGS		_IOR('U', 204, int)
+
+/* UART protocols */
+#define HCI_UART_MAX_PROTO	13
+
+#define HCI_UART_H4	0
+#define HCI_UART_BCSP	1
+#define HCI_UART_3WIRE	2
+#define HCI_UART_H4DS	3
+#define HCI_UART_LL	4
+#define HCI_UART_ATH3K	5
+#define HCI_UART_INTEL	6
+#define HCI_UART_BCM	7
+#define HCI_UART_QCA	8
+#define HCI_UART_AG6XX	9
+#define HCI_UART_NOKIA	10
+#define HCI_UART_MRVL	11
+#define HCI_UART_AML	12
+
+#define HCI_UART_RAW_DEVICE	0
+#define HCI_UART_RESET_ON_INIT	1
+#define HCI_UART_INIT_PENDING	3
+#define HCI_UART_EXT_CONFIG	4
+#define HCI_UART_VND_DETECT	5
+
+struct hci_uart;
+struct serdev_device;
+
+struct hci_uart_proto {
+	unsigned int id;
+	const char *name;
+	unsigned int manufacturer;
+	unsigned int init_speed;
+	unsigned int oper_speed;
+	int (*open)(struct hci_uart *hu);
+	int (*close)(struct hci_uart *hu);
+	int (*flush)(struct hci_uart *hu);
+	int (*setup)(struct hci_uart *hu);
+	int (*set_baudrate)(struct hci_uart *hu, unsigned int speed);
+	int (*recv)(struct hci_uart *hu, const void *data, int len);
+	int (*enqueue)(struct hci_uart *hu, struct sk_buff *skb);
+	struct sk_buff *(*dequeue)(struct hci_uart *hu);
+};
+
+struct hci_uart {
+	struct tty_struct	*tty;
+	struct serdev_device	*serdev;
+	struct hci_dev		*hdev;
+	unsigned long		flags;
+	unsigned long		hdev_flags;
+
+	struct work_struct	init_ready;
+	struct work_struct	write_work;
+
+	const struct hci_uart_proto *proto;
+	struct percpu_rw_semaphore proto_lock;	/* Stop work for proto close */
+	void			*priv;
+
+	struct sk_buff		*tx_skb;
+	unsigned long		tx_state;
+
+	unsigned int init_speed;
+	unsigned int oper_speed;
+
+	u8			alignment;
+	u8			padding;
+};
+
+/* HCI_UART proto flag bits */
+#define HCI_UART_PROTO_SET		0
+#define HCI_UART_REGISTERED		1
+#define HCI_UART_PROTO_READY		2
+#define HCI_UART_NO_SUSPEND_NOTIFIER	3
+#define HCI_UART_PROTO_INIT		4
+
+/* TX states  */
+#define HCI_UART_SENDING	1
+#define HCI_UART_TX_WAKEUP	2
+
+int hci_uart_register_proto(const struct hci_uart_proto *p);
+int hci_uart_unregister_proto(const struct hci_uart_proto *p);
+
+int hci_uart_register_device_priv(struct hci_uart *hu,
+				  const struct hci_uart_proto *p,
+				  int sizeof_priv);
+
+static inline int hci_uart_register_device(struct hci_uart *hu,
+					   const struct hci_uart_proto *p)
+{
+	return hci_uart_register_device_priv(hu, p, 0);
+}
+
+void hci_uart_unregister_device(struct hci_uart *hu);
+
+int hci_uart_tx_wakeup(struct hci_uart *hu);
+int hci_uart_wait_until_sent(struct hci_uart *hu);
+int hci_uart_init_ready(struct hci_uart *hu);
+void hci_uart_init_work(struct work_struct *work);
+void hci_uart_set_baudrate(struct hci_uart *hu, unsigned int speed);
+bool hci_uart_has_flow_control(struct hci_uart *hu);
+void hci_uart_set_flow_control(struct hci_uart *hu, bool enable);
+void hci_uart_set_speeds(struct hci_uart *hu, unsigned int init_speed,
+			 unsigned int oper_speed);
+
+struct h4_recv_pkt {
+	u8  type;	/* Packet type */
+	u8  hlen;	/* Header length */
+	u8  loff;	/* Data length offset in header */
+	u8  lsize;	/* Data length field size */
+	u16 maxlen;	/* Max overall packet length */
+	int (*recv)(struct hci_dev *hdev, struct sk_buff *skb);
+};
+
+#define H4_RECV_ACL \
+	.type = HCI_ACLDATA_PKT, \
+	.hlen = HCI_ACL_HDR_SIZE, \
+	.loff = 2, \
+	.lsize = 2, \
+	.maxlen = HCI_MAX_FRAME_SIZE \
+
+#define H4_RECV_SCO \
+	.type = HCI_SCODATA_PKT, \
+	.hlen = HCI_SCO_HDR_SIZE, \
+	.loff = 2, \
+	.lsize = 1, \
+	.maxlen = HCI_MAX_SCO_SIZE
+
+#define H4_RECV_EVENT \
+	.type = HCI_EVENT_PKT, \
+	.hlen = HCI_EVENT_HDR_SIZE, \
+	.loff = 1, \
+	.lsize = 1, \
+	.maxlen = HCI_MAX_EVENT_SIZE
+
+#define H4_RECV_ISO \
+	.type = HCI_ISODATA_PKT, \
+	.hlen = HCI_ISO_HDR_SIZE, \
+	.loff = 2, \
+	.lsize = 2, \
+	.maxlen = HCI_MAX_FRAME_SIZE \
+
+#ifdef CONFIG_BT_HCIUART_H4
+int h4_init(void);
+int h4_deinit(void);
+
+struct sk_buff *h4_recv_buf(struct hci_uart *hu, struct sk_buff *skb,
+			    const unsigned char *buffer, int count,
+			    const struct h4_recv_pkt *pkts, int pkts_count);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_BCSP
+int bcsp_init(void);
+int bcsp_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_LL
+int ll_init(void);
+int ll_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_ATH3K
+int ath_init(void);
+int ath_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_3WIRE
+int h5_init(void);
+int h5_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_INTEL
+int intel_init(void);
+int intel_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_BCM
+int bcm_init(void);
+int bcm_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_QCA
+int qca_init(void);
+int qca_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_AG6XX
+int ag6xx_init(void);
+int ag6xx_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_MRVL
+int mrvl_init(void);
+int mrvl_deinit(void);
+#endif
+
+#ifdef CONFIG_BT_HCIUART_AML
+int aml_init(void);
+int aml_deinit(void);
+#endif