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, 67 insertions, 0 deletions

diff --git a/sound/soc/sof/ipc3-priv.h b/sound/soc/sof/ipc3-priv.h
new file mode 100644
index 000000000..866c5f67b
--- /dev/null
+++ b/sound/soc/sof/ipc3-priv.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * Copyright(c) 2021 Intel Corporation
+ */
+
+#ifndef __SOUND_SOC_SOF_IPC3_PRIV_H
+#define __SOUND_SOC_SOF_IPC3_PRIV_H
+
+#include "sof-priv.h"
+
+/* IPC3 specific ops */
+extern const struct sof_ipc_pcm_ops ipc3_pcm_ops;
+extern const struct sof_ipc_tplg_ops ipc3_tplg_ops;
+extern const struct sof_ipc_tplg_control_ops tplg_ipc3_control_ops;
+extern const struct sof_ipc_fw_loader_ops ipc3_loader_ops;
+extern const struct sof_ipc_fw_tracing_ops ipc3_dtrace_ops;
+
+/* helpers for fw_ready and ext_manifest parsing */
+int sof_ipc3_get_ext_windows(struct snd_sof_dev *sdev,
+			     const struct sof_ipc_ext_data_hdr *ext_hdr);
+int sof_ipc3_get_cc_info(struct snd_sof_dev *sdev,
+			 const struct sof_ipc_ext_data_hdr *ext_hdr);
+int sof_ipc3_validate_fw_version(struct snd_sof_dev *sdev);
+
+/* dtrace position update */
+int ipc3_dtrace_posn_update(struct snd_sof_dev *sdev,
+			    struct sof_ipc_dma_trace_posn *posn);
+/* RX handler backend */
+void sof_ipc3_do_rx_work(struct snd_sof_dev *sdev, struct sof_ipc_cmd_hdr *hdr, void *msg_buf);
+
+/* dtrace platform callback wrappers */
+static inline int sof_dtrace_host_init(struct snd_sof_dev *sdev,
+				       struct snd_dma_buffer *dmatb,
+				       struct sof_ipc_dma_trace_params_ext *dtrace_params)
+{
+	const struct snd_sof_dsp_ops *dsp_ops = sdev->pdata->desc->ops;
+
+	if (dsp_ops->trace_init)
+		return dsp_ops->trace_init(sdev, dmatb, dtrace_params);
+
+	return 0;
+}
+
+static inline int sof_dtrace_host_release(struct snd_sof_dev *sdev)
+{
+	const struct snd_sof_dsp_ops *dsp_ops = sdev->pdata->desc->ops;
+
+	if (dsp_ops->trace_release)
+		return dsp_ops->trace_release(sdev);
+
+	return 0;
+}
+
+static inline int sof_dtrace_host_trigger(struct snd_sof_dev *sdev, int cmd)
+{
+	const struct snd_sof_dsp_ops *dsp_ops = sdev->pdata->desc->ops;
+
+	if (dsp_ops->trace_trigger)
+		return dsp_ops->trace_trigger(sdev, cmd);
+
+	return 0;
+}
+
+#endif