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, 204 insertions, 0 deletions

diff --git a/drivers/input/Kconfig b/drivers/input/Kconfig
new file mode 100644
index 000000000..88ecdf521
--- /dev/null
+++ b/drivers/input/Kconfig
@@ -0,0 +1,204 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Input device configuration
+#
+
+menu "Input device support"
+
+config INPUT
+	tristate "Generic input layer (needed for keyboard, mouse, ...)" if EXPERT
+	default y
+	help
+	  Say Y here if you have any input device (mouse, keyboard, tablet,
+	  joystick, steering wheel ...) connected to your system and want
+	  it to be available to applications. This includes standard PS/2
+	  keyboard and mouse.
+
+	  Say N here if you have a headless (no monitor, no keyboard) system.
+
+	  More information is available: <file:Documentation/input/input.rst>
+
+	  If unsure, say Y.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called input.
+
+if INPUT
+
+config INPUT_LEDS
+	tristate "Export input device LEDs in sysfs"
+	depends on LEDS_CLASS
+	default INPUT
+	help
+	  Say Y here if you would like to export LEDs on input devices
+	  as standard LED class devices in sysfs.
+
+	  If unsure, say Y.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called input-leds.
+
+config INPUT_FF_MEMLESS
+	tristate "Support for memoryless force-feedback devices"
+	help
+	  Say Y here if you have memoryless force-feedback input device
+	  such as Logitech WingMan Force 3D, ThrustMaster FireStorm Dual
+	  Power 2, or similar. You will also need to enable hardware-specific
+	  driver.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ff-memless.
+
+config INPUT_SPARSEKMAP
+	tristate "Sparse keymap support library"
+	help
+	  Say Y here if you are using a driver for an input
+	  device that uses sparse keymap. This option is only
+	  useful for out-of-tree drivers since in-tree drivers
+	  select it automatically.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called sparse-keymap.
+
+config INPUT_MATRIXKMAP
+	tristate "Matrix keymap support library"
+	help
+	  Say Y here if you are using a driver for an input
+	  device that uses matrix keymap. This option is only
+	  useful for out-of-tree drivers since in-tree drivers
+	  select it automatically.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called matrix-keymap.
+
+config INPUT_VIVALDIFMAP
+	tristate
+	help
+	  ChromeOS Vivaldi keymap support library. This is a hidden
+	  option so that drivers can use common code to parse and
+	  expose the vivaldi function row keymap.
+
+comment "Userland interfaces"
+
+config INPUT_MOUSEDEV
+	tristate "Mouse interface"
+	help
+	  Say Y here if you want your mouse to be accessible as char devices
+	  13:32+ - /dev/input/mouseX and 13:63 - /dev/input/mice as an
+	  emulated IntelliMouse Explorer PS/2 mouse. That way, all user space
+	  programs (including SVGAlib, GPM and X) will be able to use your
+	  mouse.
+
+	  If unsure, say Y.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mousedev.
+
+config INPUT_MOUSEDEV_PSAUX
+	bool "Provide legacy /dev/psaux device"
+	depends on INPUT_MOUSEDEV
+	help
+	  Say Y here if you want your mouse also be accessible as char device
+	  10:1 - /dev/psaux. The data available through /dev/psaux is exactly
+	  the same as the data from /dev/input/mice.
+
+	  If unsure, say Y.
+
+config INPUT_MOUSEDEV_SCREEN_X
+	int "Horizontal screen resolution"
+	depends on INPUT_MOUSEDEV
+	default "1024"
+	help
+	  If you're using a digitizer, or a graphic tablet, and want to use
+	  it as a mouse then the mousedev driver needs to know the X window
+	  screen resolution you are using to correctly scale the data. If
+	  you're not using a digitizer, this value is ignored.
+
+config INPUT_MOUSEDEV_SCREEN_Y
+	int "Vertical screen resolution"
+	depends on INPUT_MOUSEDEV
+	default "768"
+	help
+	  If you're using a digitizer, or a graphic tablet, and want to use
+	  it as a mouse then the mousedev driver needs to know the X window
+	  screen resolution you are using to correctly scale the data. If
+	  you're not using a digitizer, this value is ignored.
+
+config INPUT_JOYDEV
+	tristate "Joystick interface"
+	help
+	  Say Y here if you want your joystick or gamepad to be
+	  accessible as char device 13:0+ - /dev/input/jsX device.
+
+	  If unsure, say Y.
+
+	  More information is available: <file:Documentation/input/joydev/joystick.rst>
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called joydev.
+
+config INPUT_EVDEV
+	tristate "Event interface"
+	help
+	  Say Y here if you want your input device events be accessible
+	  under char device 13:64+ - /dev/input/eventX in a generic way.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called evdev.
+
+config INPUT_KUNIT_TEST
+	tristate "KUnit tests for Input" if !KUNIT_ALL_TESTS
+	depends on INPUT && KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Say Y here if you want to build the KUnit tests for the input
+	  subsystem.
+
+	  If in doubt, say "N".
+
+config INPUT_APMPOWER
+	tristate "Input Power Event -> APM Bridge" if EXPERT
+	depends on INPUT && APM_EMULATION
+	help
+	  Say Y here if you want suspend key events to trigger a user
+	  requested suspend through APM. This is useful on embedded
+	  systems where such behaviour is desired without userspace
+	  interaction. If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called apm-power.
+
+comment "Input Device Drivers"
+
+source "drivers/input/keyboard/Kconfig"
+
+source "drivers/input/mouse/Kconfig"
+
+source "drivers/input/joystick/Kconfig"
+
+source "drivers/input/tablet/Kconfig"
+
+source "drivers/input/touchscreen/Kconfig"
+
+source "drivers/input/misc/Kconfig"
+
+source "drivers/input/rmi4/Kconfig"
+
+endif
+
+menu "Hardware I/O ports"
+
+source "drivers/input/serio/Kconfig"
+
+source "drivers/input/gameport/Kconfig"
+
+endmenu
+
+endmenu
+