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, 66 insertions, 0 deletions

diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
new file mode 100644
index 000000000..34469711c
--- /dev/null
+++ b/drivers/video/backlight/Makefile
@@ -0,0 +1,66 @@
+# SPDX-License-Identifier: GPL-2.0
+# Backlight & LCD drivers
+
+obj-$(CONFIG_LCD_AMS369FG06)		+= ams369fg06.o
+obj-$(CONFIG_LCD_CLASS_DEVICE)		+= lcd.o
+obj-$(CONFIG_LCD_CORGI)			+= corgi_lcd.o
+obj-$(CONFIG_LCD_HP700)			+= jornada720_lcd.o
+obj-$(CONFIG_LCD_HX8357)		+= hx8357.o
+obj-$(CONFIG_LCD_ILI922X)		+= ili922x.o
+obj-$(CONFIG_LCD_ILI9320)		+= ili9320.o
+obj-$(CONFIG_LCD_L4F00242T03)		+= l4f00242t03.o
+obj-$(CONFIG_LCD_LMS283GF05)		+= lms283gf05.o
+obj-$(CONFIG_LCD_LMS501KF03)		+= lms501kf03.o
+obj-$(CONFIG_LCD_LTV350QV)		+= ltv350qv.o
+obj-$(CONFIG_LCD_OTM3225A)		+= otm3225a.o
+obj-$(CONFIG_LCD_PLATFORM)		+= platform_lcd.o
+obj-$(CONFIG_LCD_TDO24M)		+= tdo24m.o
+obj-$(CONFIG_LCD_VGG2432A4)		+= vgg2432a4.o
+
+obj-$(CONFIG_BACKLIGHT_88PM860X)	+= 88pm860x_bl.o
+obj-$(CONFIG_BACKLIGHT_AAT2870)		+= aat2870_bl.o
+obj-$(CONFIG_BACKLIGHT_ADP5520)		+= adp5520_bl.o
+obj-$(CONFIG_BACKLIGHT_ADP8860)		+= adp8860_bl.o
+obj-$(CONFIG_BACKLIGHT_ADP8870)		+= adp8870_bl.o
+obj-$(CONFIG_BACKLIGHT_APPLE)		+= apple_bl.o
+obj-$(CONFIG_BACKLIGHT_APPLE_DWI)	+= apple_dwi_bl.o
+obj-$(CONFIG_BACKLIGHT_AS3711)		+= as3711_bl.o
+obj-$(CONFIG_BACKLIGHT_AW99706)		+= aw99706.o
+obj-$(CONFIG_BACKLIGHT_BD6107)		+= bd6107.o
+obj-$(CONFIG_BACKLIGHT_CGBC)		+= cgbc_bl.o
+obj-$(CONFIG_BACKLIGHT_CLASS_DEVICE)	+= backlight.o
+obj-$(CONFIG_BACKLIGHT_DA903X)		+= da903x_bl.o
+obj-$(CONFIG_BACKLIGHT_DA9052)		+= da9052_bl.o
+obj-$(CONFIG_BACKLIGHT_EP93XX)		+= ep93xx_bl.o
+obj-$(CONFIG_BACKLIGHT_GPIO)		+= gpio_backlight.o
+obj-$(CONFIG_BACKLIGHT_HP680)		+= hp680_bl.o
+obj-$(CONFIG_BACKLIGHT_HP700)		+= jornada720_bl.o
+obj-$(CONFIG_BACKLIGHT_IPAQ_MICRO)	+= ipaq_micro_bl.o
+obj-$(CONFIG_BACKLIGHT_KTD253)		+= ktd253-backlight.o
+obj-$(CONFIG_BACKLIGHT_KTD2801)		+= ktd2801-backlight.o
+obj-$(CONFIG_BACKLIGHT_KTZ8866)		+= ktz8866.o
+obj-$(CONFIG_BACKLIGHT_LM3509)		+= lm3509_bl.o
+obj-$(CONFIG_BACKLIGHT_LM3533)		+= lm3533_bl.o
+obj-$(CONFIG_BACKLIGHT_LM3630A)		+= lm3630a_bl.o
+obj-$(CONFIG_BACKLIGHT_LM3639)		+= lm3639_bl.o
+obj-$(CONFIG_BACKLIGHT_LOCOMO)		+= locomolcd.o
+obj-$(CONFIG_BACKLIGHT_LP855X)		+= lp855x_bl.o
+obj-$(CONFIG_BACKLIGHT_LP8788)		+= lp8788_bl.o
+obj-$(CONFIG_BACKLIGHT_LV5207LP)	+= lv5207lp.o
+obj-$(CONFIG_BACKLIGHT_MAX25014)	+= max25014.o
+obj-$(CONFIG_BACKLIGHT_MAX8925)		+= max8925_bl.o
+obj-$(CONFIG_BACKLIGHT_MP3309C)		+= mp3309c.o
+obj-$(CONFIG_BACKLIGHT_MT6370)		+= mt6370-backlight.o
+obj-$(CONFIG_BACKLIGHT_OMAP1)		+= omap1_bl.o
+obj-$(CONFIG_BACKLIGHT_PANDORA)		+= pandora_bl.o
+obj-$(CONFIG_BACKLIGHT_PWM)		+= pwm_bl.o
+obj-$(CONFIG_BACKLIGHT_QCOM_WLED)	+= qcom-wled.o
+obj-$(CONFIG_BACKLIGHT_RT4831)		+= rt4831-backlight.o
+obj-$(CONFIG_BACKLIGHT_SAHARA)		+= kb3886_bl.o
+obj-$(CONFIG_BACKLIGHT_SY7758)		+= sy7758.o
+obj-$(CONFIG_BACKLIGHT_SKY81452)	+= sky81452-backlight.o
+obj-$(CONFIG_BACKLIGHT_TPS65217)	+= tps65217_bl.o
+obj-$(CONFIG_BACKLIGHT_WM831X)		+= wm831x_bl.o
+obj-$(CONFIG_BACKLIGHT_ARCXCNN) 	+= arcxcnn_bl.o
+obj-$(CONFIG_BACKLIGHT_RAVE_SP)		+= rave-sp-backlight.o
+obj-$(CONFIG_BACKLIGHT_LED)		+= led_bl.o