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, 90 insertions, 0 deletions

diff --git a/include/sound/initval.h b/include/sound/initval.h
new file mode 100644
index 000000000..a1ff3b486
--- /dev/null
+++ b/include/sound/initval.h
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __SOUND_INITVAL_H
+#define __SOUND_INITVAL_H
+
+/*
+ *  Init values for soundcard modules
+ *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ */
+
+#define SNDRV_AUTO_PORT		1
+#define SNDRV_AUTO_IRQ		0xffff
+#define SNDRV_AUTO_DMA		0xffff
+#define SNDRV_AUTO_DMA_SIZE	(0x7fffffff)
+
+#define SNDRV_DEFAULT_IDX1	(-1)
+#define SNDRV_DEFAULT_STR1	NULL
+#define SNDRV_DEFAULT_ENABLE1	1
+#define SNDRV_DEFAULT_PORT1	SNDRV_AUTO_PORT
+#define SNDRV_DEFAULT_IRQ1	SNDRV_AUTO_IRQ
+#define SNDRV_DEFAULT_DMA1	SNDRV_AUTO_DMA
+#define SNDRV_DEFAULT_DMA_SIZE1	SNDRV_AUTO_DMA_SIZE
+#define SNDRV_DEFAULT_PTR1	SNDRV_DEFAULT_STR1
+
+#define SNDRV_DEFAULT_IDX	{ [0 ... (SNDRV_CARDS-1)] = -1 }
+#define SNDRV_DEFAULT_STR	{ [0 ... (SNDRV_CARDS-1)] = NULL }
+#define SNDRV_DEFAULT_ENABLE	{ 1, [1 ... (SNDRV_CARDS-1)] = 0 }
+#define SNDRV_DEFAULT_ENABLE_PNP { [0 ... (SNDRV_CARDS-1)] = 1 }
+#ifdef CONFIG_PNP
+#define SNDRV_DEFAULT_ENABLE_ISAPNP SNDRV_DEFAULT_ENABLE_PNP
+#else
+#define SNDRV_DEFAULT_ENABLE_ISAPNP SNDRV_DEFAULT_ENABLE
+#endif
+#define SNDRV_DEFAULT_PORT	{ [0 ... (SNDRV_CARDS-1)] = SNDRV_AUTO_PORT }
+#define SNDRV_DEFAULT_IRQ	{ [0 ... (SNDRV_CARDS-1)] = SNDRV_AUTO_IRQ }
+#define SNDRV_DEFAULT_DMA	{ [0 ... (SNDRV_CARDS-1)] = SNDRV_AUTO_DMA }
+#define SNDRV_DEFAULT_DMA_SIZE	{ [0 ... (SNDRV_CARDS-1)] = SNDRV_AUTO_DMA_SIZE }
+#define SNDRV_DEFAULT_PTR	SNDRV_DEFAULT_STR
+
+#ifdef SNDRV_LEGACY_FIND_FREE_IOPORT
+static long snd_legacy_find_free_ioport(const long *port_table, long size)
+{
+	while (*port_table != -1) {
+		if (request_region(*port_table, size, "ALSA test")) {
+			release_region(*port_table, size);
+			return *port_table;
+		}
+		port_table++;
+	}
+	return -1;
+}
+#endif
+
+#ifdef SNDRV_LEGACY_FIND_FREE_IRQ
+#include <linux/interrupt.h>
+
+static irqreturn_t snd_legacy_empty_irq_handler(int irq, void *dev_id)
+{
+	return IRQ_HANDLED;
+}
+
+static int snd_legacy_find_free_irq(const int *irq_table)
+{
+	while (*irq_table != -1) {
+		if (!request_irq(*irq_table, snd_legacy_empty_irq_handler,
+				 IRQF_PROBE_SHARED, "ALSA Test IRQ",
+				 (void *) irq_table)) {
+			free_irq(*irq_table, (void *) irq_table);
+			return *irq_table;
+		}
+		irq_table++;
+	}
+	return -1;
+}
+#endif
+
+#ifdef SNDRV_LEGACY_FIND_FREE_DMA
+static int snd_legacy_find_free_dma(const int *dma_table)
+{
+	while (*dma_table != -1) {
+		if (!request_dma(*dma_table, "ALSA Test DMA")) {
+			free_dma(*dma_table);
+			return *dma_table;
+		}
+		dma_table++;
+	}
+	return -1;
+}
+#endif
+
+#endif /* __SOUND_INITVAL_H */