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, 140 insertions, 0 deletions

diff --git a/include/sound/hdmi-codec.h b/include/sound/hdmi-codec.h
new file mode 100644
index 000000000..273f4c36f
--- /dev/null
+++ b/include/sound/hdmi-codec.h
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * hdmi-codec.h - HDMI Codec driver API
+ *
+ * Copyright (C) 2014 Texas Instruments Incorporated - https://www.ti.com
+ *
+ * Author: Jyri Sarha <jsarha@ti.com>
+ */
+
+#ifndef __HDMI_CODEC_H__
+#define __HDMI_CODEC_H__
+
+#include <linux/of_graph.h>
+#include <linux/hdmi.h>
+#include <sound/asoundef.h>
+#include <sound/soc.h>
+#include <uapi/sound/asound.h>
+
+/*
+ * Protocol between ASoC cpu-dai and HDMI-encoder
+ */
+struct hdmi_codec_daifmt {
+	enum {
+		HDMI_I2S,
+		HDMI_RIGHT_J,
+		HDMI_LEFT_J,
+		HDMI_DSP_A,
+		HDMI_DSP_B,
+		HDMI_AC97,
+		HDMI_SPDIF,
+	} fmt;
+	unsigned int bit_clk_inv:1;
+	unsigned int frame_clk_inv:1;
+	unsigned int bit_clk_provider:1;
+	unsigned int frame_clk_provider:1;
+	/* bit_fmt could be standard PCM format or
+	 * IEC958 encoded format. ALSA IEC958 plugin will pass
+	 * IEC958_SUBFRAME format to the underneath driver.
+	 */
+	snd_pcm_format_t bit_fmt;
+};
+
+/*
+ * HDMI audio parameters
+ */
+struct hdmi_codec_params {
+	struct hdmi_audio_infoframe cea;
+	struct snd_aes_iec958 iec;
+	int sample_rate;
+	int sample_width;
+	int channels;
+};
+
+typedef void (*hdmi_codec_plugged_cb)(struct device *dev,
+				      bool plugged);
+
+struct hdmi_codec_pdata;
+struct hdmi_codec_ops {
+	/*
+	 * Called when ASoC starts an audio stream setup.
+	 * Optional
+	 */
+	int (*audio_startup)(struct device *dev, void *data);
+
+	/*
+	 * Configures HDMI-encoder for audio stream.
+	 * Having either prepare or hw_params is mandatory.
+	 */
+	int (*hw_params)(struct device *dev, void *data,
+			 struct hdmi_codec_daifmt *fmt,
+			 struct hdmi_codec_params *hparms);
+
+	/*
+	 * Configures HDMI-encoder for audio stream. Can be called
+	 * multiple times for each setup.
+	 *
+	 * Having either prepare or hw_params is mandatory.
+	 */
+	int (*prepare)(struct device *dev, void *data,
+		       struct hdmi_codec_daifmt *fmt,
+		       struct hdmi_codec_params *hparms);
+
+	/*
+	 * Shuts down the audio stream.
+	 * Mandatory
+	 */
+	void (*audio_shutdown)(struct device *dev, void *data);
+
+	/*
+	 * Mute/unmute HDMI audio stream.
+	 * Optional
+	 */
+	int (*mute_stream)(struct device *dev, void *data,
+			   bool enable, int direction);
+
+	/*
+	 * Provides EDID-Like-Data from connected HDMI device.
+	 * Optional
+	 */
+	int (*get_eld)(struct device *dev, void *data,
+		       uint8_t *buf, size_t len);
+
+	/*
+	 * Getting DAI ID
+	 * Optional
+	 */
+	int (*get_dai_id)(struct snd_soc_component *comment,
+			  struct device_node *endpoint,
+			  void *data);
+
+	/*
+	 * Hook callback function to handle connector plug event.
+	 * Optional
+	 */
+	int (*hook_plugged_cb)(struct device *dev, void *data,
+			       hdmi_codec_plugged_cb fn,
+			       struct device *codec_dev);
+};
+
+/* HDMI codec initalization data */
+struct hdmi_codec_pdata {
+	const struct hdmi_codec_ops *ops;
+	u64 i2s_formats;
+	uint i2s:1;
+	uint no_i2s_playback:1;
+	uint no_i2s_capture:1;
+	uint spdif:1;
+	uint no_spdif_playback:1;
+	uint no_spdif_capture:1;
+	uint no_capture_mute:1;
+	int max_i2s_channels;
+	void *data;
+};
+
+struct snd_soc_component;
+struct snd_soc_jack;
+
+#define HDMI_CODEC_DRV_NAME "hdmi-audio-codec"
+
+#endif /* __HDMI_CODEC_H__ */