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, 117 insertions, 0 deletions

diff --git a/drivers/bluetooth/btbcm.h b/drivers/bluetooth/btbcm.h
new file mode 100644
index 000000000..b4cb24231
--- /dev/null
+++ b/drivers/bluetooth/btbcm.h
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *
+ *  Bluetooth support for Broadcom devices
+ *
+ *  Copyright (C) 2015  Intel Corporation
+ */
+
+#define BCM_UART_CLOCK_48MHZ	0x01
+#define BCM_UART_CLOCK_24MHZ	0x02
+
+struct bcm_update_uart_baud_rate {
+	__le16 zero;
+	__le32 baud_rate;
+} __packed;
+
+struct bcm_write_uart_clock_setting {
+	__u8 type;
+} __packed;
+
+struct bcm_set_sleep_mode {
+	__u8 sleep_mode;
+	__u8 idle_host;
+	__u8 idle_dev;
+	__u8 bt_wake_active;
+	__u8 host_wake_active;
+	__u8 allow_host_sleep;
+	__u8 combine_modes;
+	__u8 tristate_control;
+	__u8 usb_auto_sleep;
+	__u8 usb_resume_timeout;
+	__u8 break_to_host;
+	__u8 pulsed_host_wake;
+} __packed;
+
+struct bcm_set_pcm_int_params {
+	__u8 routing;
+	__u8 rate;
+	__u8 frame_sync;
+	__u8 sync_mode;
+	__u8 clock_mode;
+} __packed;
+
+struct bcm_set_pcm_format_params {
+	__u8 lsb_first;
+	__u8 fill_value;
+	__u8 fill_method;
+	__u8 fill_num;
+	__u8 right_justify;
+} __packed;
+
+#if IS_ENABLED(CONFIG_BT_BCM)
+
+int btbcm_check_bdaddr(struct hci_dev *hdev);
+int btbcm_set_bdaddr(struct hci_dev *hdev, const bdaddr_t *bdaddr);
+int btbcm_patchram(struct hci_dev *hdev, const struct firmware *fw);
+int btbcm_read_pcm_int_params(struct hci_dev *hdev,
+			      struct bcm_set_pcm_int_params *params);
+int btbcm_write_pcm_int_params(struct hci_dev *hdev,
+			       const struct bcm_set_pcm_int_params *params);
+
+int btbcm_setup_patchram(struct hci_dev *hdev);
+int btbcm_setup_apple(struct hci_dev *hdev);
+
+int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode);
+int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode);
+
+#else
+
+static inline int btbcm_check_bdaddr(struct hci_dev *hdev)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int btbcm_set_bdaddr(struct hci_dev *hdev, const bdaddr_t *bdaddr)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int btbcm_read_pcm_int_params(struct hci_dev *hdev,
+			      struct bcm_set_pcm_int_params *params)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int btbcm_write_pcm_int_params(struct hci_dev *hdev,
+			       const struct bcm_set_pcm_int_params *params)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int btbcm_patchram(struct hci_dev *hdev, const struct firmware *fw)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int btbcm_setup_patchram(struct hci_dev *hdev)
+{
+	return 0;
+}
+
+static inline int btbcm_setup_apple(struct hci_dev *hdev)
+{
+	return 0;
+}
+
+static inline int btbcm_initialize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode)
+{
+	return 0;
+}
+
+static inline int btbcm_finalize(struct hci_dev *hdev, bool *fw_load_done, bool use_autobaud_mode)
+{
+	return 0;
+}
+
+#endif