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, 145 insertions, 0 deletions

diff --git a/drivers/input/rmi4/Kconfig b/drivers/input/rmi4/Kconfig
new file mode 100644
index 000000000..5db58fc9e
--- /dev/null
+++ b/drivers/input/rmi4/Kconfig
@@ -0,0 +1,145 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# RMI4 configuration
+#
+config RMI4_CORE
+	tristate "Synaptics RMI4 bus support"
+	select IRQ_DOMAIN
+	help
+	  Say Y here if you want to support the Synaptics RMI4 bus.  This is
+	  required for all RMI4 device support.
+
+	  If unsure, say Y.
+
+if RMI4_CORE
+
+config RMI4_I2C
+	tristate "RMI4 I2C Support"
+	depends on I2C
+	help
+	  Say Y here if you want to support RMI4 devices connected to an I2C
+	  bus.
+
+	  If unsure, say Y.
+
+config RMI4_SPI
+	tristate "RMI4 SPI Support"
+	depends on SPI
+	help
+	  Say Y here if you want to support RMI4 devices connected to a SPI
+	  bus.
+
+	  If unsure, say N.
+
+config RMI4_SMB
+	tristate "RMI4 SMB Support"
+	depends on I2C
+	help
+	  Say Y here if you want to support RMI4 devices connected to an SMB
+	  bus.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called rmi_smbus.
+
+config RMI4_F03
+	bool "RMI4 Function 03 (PS2 Guest)"
+	depends on RMI4_CORE
+	help
+	  Say Y here if you want to add support for RMI4 function 03.
+
+	  Function 03 provides PS2 guest support for RMI4 devices. This
+	  includes support for TrackPoints on TouchPads.
+
+config RMI4_F03_SERIO
+	tristate
+	depends on RMI4_CORE
+	depends on RMI4_F03
+	default RMI4_CORE
+	select SERIO
+
+config RMI4_2D_SENSOR
+	bool
+
+config RMI4_F11
+	bool "RMI4 Function 11 (2D pointing)"
+	select RMI4_2D_SENSOR
+	help
+	  Say Y here if you want to add support for RMI4 function 11.
+
+	  Function 11 provides 2D multifinger pointing for touchscreens and
+	  touchpads. For sensors that support relative pointing, F11 also
+	  provides mouse input.
+
+config RMI4_F12
+	bool "RMI4 Function 12 (2D pointing)"
+	select RMI4_2D_SENSOR
+	help
+	  Say Y here if you want to add support for RMI4 function 12.
+
+	  Function 12 provides 2D multifinger pointing for touchscreens and
+	  touchpads. For sensors that support relative pointing, F12 also
+	  provides mouse input.
+
+config RMI4_F1A
+	bool "RMI4 Function 1A (0D pointing)"
+	help
+	  Say Y here if you want to add support for RMI4 function 1A.
+
+	  Function 1A provides capacitive keys support for RMI4 devices.
+
+config RMI4_F21
+	bool "RMI4 Function 21 (PRESSURE)"
+	help
+	  Say Y here if you want to add support for RMI4 function 21.
+
+	  Function 21 provides buttons/pressure handling for RMI4 devices.
+	  This includes support for buttons/pressure on PressurePad.
+
+config RMI4_F30
+	bool "RMI4 Function 30 (GPIO LED)"
+	help
+	  Say Y here if you want to add support for RMI4 function 30.
+
+	  Function 30 provides GPIO and LED support for RMI4 devices. This
+	  includes support for buttons on TouchPads and ClickPads.
+
+config RMI4_F34
+	bool "RMI4 Function 34 (Device reflash)"
+	select FW_LOADER
+	help
+	  Say Y here if you want to add support for RMI4 function 34.
+
+	  Function 34 provides support for upgrading the firmware on the RMI4
+	  device via the firmware loader interface. This is triggered using a
+	  sysfs attribute.
+
+config RMI4_F3A
+	bool "RMI4 Function 3A (GPIO)"
+	help
+	  Say Y here if you want to add support for RMI4 function 3A.
+
+	  Function 3A provides GPIO support for RMI4 devices. This includes
+	  support for buttons on TouchPads and ClickPads.
+
+config RMI4_F54
+	bool "RMI4 Function 54 (Analog diagnostics)"
+	depends on VIDEO_DEV=y || (RMI4_CORE=m && VIDEO_DEV=m)
+	select VIDEOBUF2_VMALLOC
+	select RMI4_F55
+	help
+	  Say Y here if you want to add support for RMI4 function 54
+
+	  Function 54 provides access to various diagnostic features in certain
+	  RMI4 touch sensors.
+
+config RMI4_F55
+	bool "RMI4 Function 55 (Sensor tuning)"
+	help
+	  Say Y here if you want to add support for RMI4 function 55
+
+	  Function 55 provides access to the RMI4 touch sensor tuning
+	  mechanism.
+
+endif # RMI_CORE