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, 175 insertions, 0 deletions

diff --git a/drivers/pinctrl/intel/Kconfig b/drivers/pinctrl/intel/Kconfig
new file mode 100644
index 000000000..04c3a5b58
--- /dev/null
+++ b/drivers/pinctrl/intel/Kconfig
@@ -0,0 +1,175 @@
+# SPDX-License-Identifier: GPL-2.0
+# Intel pin control drivers
+menu "Intel pinctrl drivers"
+	depends on (ACPI && X86) || COMPILE_TEST
+
+config PINCTRL_BAYTRAIL
+	bool "Intel Baytrail GPIO pin control"
+	select PINCTRL_INTEL
+	help
+	  driver for memory mapped GPIO functionality on Intel Baytrail
+	  platforms. Supports 3 banks with 102, 28 and 44 gpios.
+	  Most pins are usually muxed to some other functionality by firmware,
+	  so only a small amount is available for gpio use.
+
+	  Requires ACPI device enumeration code to set up a platform device.
+
+config PINCTRL_CHERRYVIEW
+	tristate "Intel Cherryview/Braswell pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  Cherryview/Braswell pinctrl driver provides an interface that
+	  allows configuring of SoC pins and using them as GPIOs.
+
+config PINCTRL_LYNXPOINT
+	tristate "Intel Lynxpoint pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  Lynxpoint is the PCH of Intel Haswell. This pinctrl driver
+	  provides an interface that allows configuring of PCH pins and
+	  using them as GPIOs.
+
+config PINCTRL_INTEL
+	tristate
+	select PINMUX
+	select PINCONF
+	select GENERIC_PINCONF
+	select GPIOLIB
+	select GPIOLIB_IRQCHIP
+
+config PINCTRL_INTEL_PLATFORM
+	tristate "Intel pinctrl and GPIO platform driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel PCH pins and using them as GPIOs. Currently the following
+	  Intel SoCs / platforms require this to be functional:
+	  - Lunar Lake
+	  - Nova Lake
+	  - Panther Lake
+
+config PINCTRL_ALDERLAKE
+	tristate "Intel Alder Lake pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  PCH pins of the following platforms and using them as GPIOs:
+	  - Alder Lake HX, N, and S
+	  - Raptor Lake HX, E, and S
+	  - Twin Lake
+
+config PINCTRL_BROXTON
+	tristate "Intel Broxton pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  Broxton pinctrl driver provides an interface that allows
+	  configuring of SoC pins and using them as GPIOs.
+
+config PINCTRL_CANNONLAKE
+	tristate "Intel Cannon Lake PCH pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Cannon Lake PCH pins and using them as GPIOs.
+
+config PINCTRL_CEDARFORK
+	tristate "Intel Cedar Fork pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Cedar Fork PCH pins and using them as GPIOs.
+
+config PINCTRL_DENVERTON
+	tristate "Intel Denverton pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Denverton SoC pins and using them as GPIOs.
+
+config PINCTRL_ELKHARTLAKE
+	tristate "Intel Elkhart Lake SoC pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Elkhart Lake SoC pins and using them as GPIOs.
+
+config PINCTRL_EMMITSBURG
+	tristate "Intel Emmitsburg pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Emmitsburg pins and using them as GPIOs.
+
+config PINCTRL_GEMINILAKE
+	tristate "Intel Gemini Lake SoC pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Gemini Lake SoC pins and using them as GPIOs.
+
+config PINCTRL_ICELAKE
+	tristate "Intel Ice Lake PCH pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Ice Lake PCH pins and using them as GPIOs.
+
+config PINCTRL_JASPERLAKE
+	tristate "Intel Jasper Lake PCH pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Jasper Lake PCH pins and using them as GPIOs.
+
+config PINCTRL_LAKEFIELD
+	tristate "Intel Lakefield SoC pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Lakefield SoC pins and using them as GPIOs.
+
+config PINCTRL_LEWISBURG
+	tristate "Intel Lewisburg pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  of Intel Lewisburg pins and using them as GPIOs.
+
+config PINCTRL_METEORLAKE
+	tristate "Intel Meteor Lake pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  SoC pins of the following platforms and using them as GPIOs:
+	  - Arrow Lake (all variants)
+	  - Meteor Lake (all variants)
+
+config PINCTRL_METEORPOINT
+	tristate "Intel Meteor Point pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  PCH pins of the following platforms and using them as GPIOs:
+	  - Arrow Lake HX and S
+
+config PINCTRL_SUNRISEPOINT
+	tristate "Intel Sunrisepoint pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  Sunrisepoint is the PCH of Intel Skylake. This pinctrl driver
+	  provides an interface that allows configuring of PCH pins and
+	  using them as GPIOs.
+
+config PINCTRL_TIGERLAKE
+	tristate "Intel Tiger Lake pinctrl and GPIO driver"
+	select PINCTRL_INTEL
+	help
+	  This pinctrl driver provides an interface that allows configuring
+	  PCH pins of the following platforms and using them as GPIOs:
+	  - Alder Lake H, P, PS, and U
+	  - Raptor Lake H, P, PS, PX, and U
+	  - Rocket Lake S
+	  - Tiger Lake (all variants)
+
+source "drivers/pinctrl/intel/Kconfig.tng"
+endmenu