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, 120 insertions, 0 deletions

diff --git a/include/video/pxa168fb.h b/include/video/pxa168fb.h
new file mode 100644
index 000000000..6e278248d
--- /dev/null
+++ b/include/video/pxa168fb.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  Copyright (C) 2009 Marvell International Ltd.
+ */
+
+#ifndef __ASM_MACH_PXA168FB_H
+#define __ASM_MACH_PXA168FB_H
+
+#include <linux/fb.h>
+#include <linux/interrupt.h>
+
+/* Dumb interface */
+#define PIN_MODE_DUMB_24		0
+#define PIN_MODE_DUMB_18_SPI		1
+#define PIN_MODE_DUMB_18_GPIO		2
+#define PIN_MODE_DUMB_16_SPI		3
+#define PIN_MODE_DUMB_16_GPIO		4
+#define PIN_MODE_DUMB_12_SPI_GPIO	5
+#define PIN_MODE_SMART_18_SPI		6
+#define PIN_MODE_SMART_16_SPI		7
+#define PIN_MODE_SMART_8_SPI_GPIO	8
+
+/* Dumb interface pin allocation */
+#define DUMB_MODE_RGB565		0
+#define DUMB_MODE_RGB565_UPPER		1
+#define DUMB_MODE_RGB666		2
+#define DUMB_MODE_RGB666_UPPER		3
+#define DUMB_MODE_RGB444		4
+#define DUMB_MODE_RGB444_UPPER		5
+#define DUMB_MODE_RGB888		6
+
+/* default fb buffer size WVGA-32bits */
+#define DEFAULT_FB_SIZE	(800 * 480 * 4)
+
+/*
+ * Buffer pixel format
+ * bit0 is for rb swap.
+ * bit12 is for Y UorV swap
+ */
+#define PIX_FMT_RGB565		0
+#define PIX_FMT_BGR565		1
+#define PIX_FMT_RGB1555		2
+#define PIX_FMT_BGR1555		3
+#define PIX_FMT_RGB888PACK	4
+#define PIX_FMT_BGR888PACK	5
+#define PIX_FMT_RGB888UNPACK	6
+#define PIX_FMT_BGR888UNPACK	7
+#define PIX_FMT_RGBA888		8
+#define PIX_FMT_BGRA888		9
+#define PIX_FMT_YUV422PACK	10
+#define PIX_FMT_YVU422PACK	11
+#define PIX_FMT_YUV422PLANAR	12
+#define PIX_FMT_YVU422PLANAR	13
+#define PIX_FMT_YUV420PLANAR	14
+#define PIX_FMT_YVU420PLANAR	15
+#define PIX_FMT_PSEUDOCOLOR	20
+#define PIX_FMT_UYVY422PACK	(0x1000|PIX_FMT_YUV422PACK)
+
+/*
+ * PXA LCD controller private state.
+ */
+struct pxa168fb_info {
+	struct device		*dev;
+	struct clk		*clk;
+	struct fb_info		*info;
+
+	void __iomem		*reg_base;
+	dma_addr_t		fb_start_dma;
+	u32			pseudo_palette[16];
+
+	int			pix_fmt;
+	unsigned		is_blanked:1;
+	unsigned		panel_rbswap:1;
+	unsigned		active:1;
+};
+
+/*
+ * PXA fb machine information
+ */
+struct pxa168fb_mach_info {
+	char	id[16];
+
+	int		num_modes;
+	struct fb_videomode *modes;
+
+	/*
+	 * Pix_fmt
+	 */
+	unsigned	pix_fmt;
+
+	/*
+	 * I/O pin allocation.
+	 */
+	unsigned	io_pin_allocation_mode:4;
+
+	/*
+	 * Dumb panel -- assignment of R/G/B component info to the 24
+	 * available external data lanes.
+	 */
+	unsigned	dumb_mode:4;
+	unsigned	panel_rgb_reverse_lanes:1;
+
+	/*
+	 * Dumb panel -- GPIO output data.
+	 */
+	unsigned	gpio_output_mask:8;
+	unsigned	gpio_output_data:8;
+
+	/*
+	 * Dumb panel -- configurable output signal polarity.
+	 */
+	unsigned	invert_composite_blank:1;
+	unsigned	invert_pix_val_ena:1;
+	unsigned	invert_pixclock:1;
+	unsigned	panel_rbswap:1;
+	unsigned	active:1;
+	unsigned	enable_lcd:1;
+};
+
+#endif /* __ASM_MACH_PXA168FB_H */