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, 162 insertions, 0 deletions

diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
new file mode 100644
index 000000000..abf8c6cde
--- /dev/null
+++ b/drivers/usb/Kconfig
@@ -0,0 +1,162 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# USB device configuration
+#
+
+config USB_OHCI_BIG_ENDIAN_DESC
+	bool
+
+config USB_OHCI_BIG_ENDIAN_MMIO
+	bool
+
+config USB_OHCI_LITTLE_ENDIAN
+	bool
+	default n if PPC_MPC52xx
+	default y
+
+config USB_EHCI_BIG_ENDIAN_MMIO
+	bool
+
+config USB_EHCI_BIG_ENDIAN_DESC
+	bool
+
+config USB_UHCI_BIG_ENDIAN_MMIO
+	bool
+
+config USB_UHCI_BIG_ENDIAN_DESC
+	bool
+
+menuconfig USB_SUPPORT
+	bool "USB support"
+	depends on HAS_IOMEM
+	default y
+	help
+	  This option adds core support for Universal Serial Bus (USB).
+	  You will also need drivers from the following menu to make use of it.
+
+if USB_SUPPORT
+
+source "drivers/usb/common/Kconfig"
+
+config USB_ARCH_HAS_HCD
+	def_bool y
+
+config USB
+	tristate "Support for Host-side USB"
+	depends on USB_ARCH_HAS_HCD
+	select GENERIC_ALLOCATOR
+	select USB_COMMON
+	select NLS  # for UTF-8 strings
+	help
+	  Universal Serial Bus (USB) is a specification for a serial bus
+	  subsystem which offers higher speeds and more features than the
+	  traditional PC serial port.  The bus supplies power to peripherals
+	  and allows for hot swapping.  Up to 127 USB peripherals can be
+	  connected to a single USB host in a tree structure.
+	  
+	  The USB host is the root of the tree, the peripherals are the
+	  leaves and the inner nodes are special USB devices called hubs.
+	  Most PCs now have USB host ports, used to connect peripherals
+	  such as scanners, keyboards, mice, modems, cameras, disks,
+	  flash memory, network links, and printers to the PC.
+
+	  Say Y here if your computer has a host-side USB port and you want
+	  to use USB devices.  You then need to say Y to at least one of the
+	  Host Controller Driver (HCD) options below.  Choose a USB 1.1
+	  controller, such as "UHCI HCD support" or "OHCI HCD support",
+	  and "EHCI HCD (USB 2.0) support" except for older systems that
+	  do not have USB 2.0 support.  It doesn't normally hurt to select
+	  them all if you are not certain.
+
+	  If your system has a device-side USB port, used in the peripheral
+	  side of the USB protocol, see the "USB Gadget" framework instead.
+
+	  After choosing your HCD, then select drivers for the USB peripherals
+	  you'll be using.  You may want to check out the information provided
+	  in <file:Documentation/usb/> and especially the links given in
+	  <file:Documentation/usb/usb-help.rst>.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called usbcore.
+
+config USB_PCI
+	bool "PCI based USB host interface"
+	depends on PCI
+	default y
+	help
+	  Many embedded system SOCs (e.g. freescale T2080) have both
+	  PCI and USB modules with the USB module directly controlled by
+	  registers and having no relationship to the PCI module.
+
+	  If you have such a device you may say N here and PCI related code
+	  will not be built in the USB driver.
+
+config USB_PCI_AMD
+	bool "AMD PCI USB host support"
+	depends on USB_PCI && HAS_IOPORT
+	default X86 || MACH_LOONGSON64 || PPC_PASEMI
+	help
+	  Enable workarounds for USB implementation quirks in SB600/SB700/SB800
+	  and later south bridge implementations. These are common on x86 PCs
+	  with AMD CPUs but rarely used elsewhere, with the exception of a few
+	  powerpc and mips desktop machines.
+
+if USB
+
+source "drivers/usb/core/Kconfig"
+
+source "drivers/usb/mon/Kconfig"
+
+source "drivers/usb/host/Kconfig"
+
+source "drivers/usb/renesas_usbhs/Kconfig"
+
+source "drivers/usb/class/Kconfig"
+
+source "drivers/usb/storage/Kconfig"
+
+source "drivers/usb/image/Kconfig"
+
+source "drivers/usb/usbip/Kconfig"
+
+endif
+
+comment "USB dual-mode controller drivers"
+
+source "drivers/usb/cdns3/Kconfig"
+
+source "drivers/usb/fotg210/Kconfig"
+
+source "drivers/usb/mtu3/Kconfig"
+
+source "drivers/usb/musb/Kconfig"
+
+source "drivers/usb/dwc3/Kconfig"
+
+source "drivers/usb/dwc2/Kconfig"
+
+source "drivers/usb/chipidea/Kconfig"
+
+source "drivers/usb/isp1760/Kconfig"
+
+comment "USB port drivers"
+
+if USB
+
+source "drivers/usb/serial/Kconfig"
+
+source "drivers/usb/misc/Kconfig"
+
+source "drivers/usb/atm/Kconfig"
+
+endif # USB
+
+source "drivers/usb/phy/Kconfig"
+
+source "drivers/usb/gadget/Kconfig"
+
+source "drivers/usb/typec/Kconfig"
+
+source "drivers/usb/roles/Kconfig"
+
+endif # USB_SUPPORT