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, 79 insertions, 0 deletions

diff --git a/sound/soc/sof/sof-client.h b/sound/soc/sof/sof-client.h
new file mode 100644
index 000000000..3b02506c0
--- /dev/null
+++ b/sound/soc/sof/sof-client.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __SOC_SOF_CLIENT_H
+#define __SOC_SOF_CLIENT_H
+
+#include <linux/auxiliary_bus.h>
+#include <linux/device.h>
+#include <linux/list.h>
+#include <sound/sof.h>
+
+struct sof_ipc_fw_version;
+struct sof_ipc_cmd_hdr;
+struct snd_sof_dev;
+struct dentry;
+
+struct sof_ipc4_fw_module;
+
+/**
+ * struct sof_client_dev - SOF client device
+ * @auxdev:	auxiliary device
+ * @data:	device specific data
+ */
+struct sof_client_dev {
+	struct auxiliary_device auxdev;
+	void *data;
+};
+
+#define auxiliary_dev_to_sof_client_dev(auxiliary_dev) \
+	container_of(auxiliary_dev, struct sof_client_dev, auxdev)
+
+#define dev_to_sof_client_dev(dev) \
+	container_of(to_auxiliary_dev(dev), struct sof_client_dev, auxdev)
+
+int sof_client_ipc_tx_message(struct sof_client_dev *cdev, void *ipc_msg,
+			      void *reply_data, size_t reply_bytes);
+static inline int sof_client_ipc_tx_message_no_reply(struct sof_client_dev *cdev, void *ipc_msg)
+{
+	return sof_client_ipc_tx_message(cdev, ipc_msg, NULL, 0);
+}
+int sof_client_ipc_set_get_data(struct sof_client_dev *cdev, void *ipc_msg,
+				bool set);
+
+struct sof_ipc4_fw_module *sof_client_ipc4_find_module(struct sof_client_dev *c, const guid_t *u);
+struct snd_sof_widget *sof_client_ipc4_find_swidget_by_id(struct sof_client_dev *cdev,
+							  u32 module_id, int instance_id);
+
+struct dentry *sof_client_get_debugfs_root(struct sof_client_dev *cdev);
+struct device *sof_client_get_dma_dev(struct sof_client_dev *cdev);
+const struct sof_ipc_fw_version *sof_client_get_fw_version(struct sof_client_dev *cdev);
+size_t sof_client_get_ipc_max_payload_size(struct sof_client_dev *cdev);
+enum sof_ipc_type sof_client_get_ipc_type(struct sof_client_dev *cdev);
+
+/* DSP/firmware boot request */
+int sof_client_boot_dsp(struct sof_client_dev *cdev);
+
+/* module refcount management of SOF core */
+int sof_client_core_module_get(struct sof_client_dev *cdev);
+void sof_client_core_module_put(struct sof_client_dev *cdev);
+
+/* IPC notification */
+typedef void (*sof_client_event_callback)(struct sof_client_dev *cdev, void *msg_buf);
+
+int sof_client_register_ipc_rx_handler(struct sof_client_dev *cdev,
+				       u32 ipc_msg_type,
+				       sof_client_event_callback callback);
+void sof_client_unregister_ipc_rx_handler(struct sof_client_dev *cdev,
+					  u32 ipc_msg_type);
+
+/* DSP state notification and query */
+typedef void (*sof_client_fw_state_callback)(struct sof_client_dev *cdev,
+					     enum sof_fw_state state);
+
+int sof_client_register_fw_state_handler(struct sof_client_dev *cdev,
+					 sof_client_fw_state_callback callback);
+void sof_client_unregister_fw_state_handler(struct sof_client_dev *cdev);
+enum sof_fw_state sof_client_get_fw_state(struct sof_client_dev *cdev);
+int sof_client_ipc_rx_message(struct sof_client_dev *cdev, void *ipc_msg, void *msg_buf);
+
+#endif /* __SOC_SOF_CLIENT_H */