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, 64 insertions, 0 deletions

diff --git a/drivers/usb/chipidea/Kconfig b/drivers/usb/chipidea/Kconfig
new file mode 100644
index 000000000..bab45bc62
--- /dev/null
+++ b/drivers/usb/chipidea/Kconfig
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config USB_CHIPIDEA
+	tristate "ChipIdea Highspeed Dual Role Controller"
+	depends on ((USB_EHCI_HCD && USB_GADGET) || (USB_EHCI_HCD && !USB_GADGET) || (!USB_EHCI_HCD && USB_GADGET)) && HAS_DMA
+	select EXTCON
+	select RESET_CONTROLLER
+	select USB_ULPI_BUS
+	select USB_ROLE_SWITCH
+	select USB_TEGRA_PHY if ARCH_TEGRA
+	help
+	  Say Y here if your system has a dual role high speed USB
+	  controller based on ChipIdea silicon IP. It supports:
+	  Dual-role switch (ID, OTG FSM, sysfs), Host-only, and
+	  Peripheral-only.
+
+	  When compiled dynamically, the module will be called ci_hdrc.ko.
+
+if USB_CHIPIDEA
+
+config USB_CHIPIDEA_UDC
+	bool "ChipIdea device controller"
+	depends on USB_GADGET
+	help
+	  Say Y here to enable device controller functionality of the
+	  ChipIdea driver.
+
+config USB_CHIPIDEA_HOST
+	bool "ChipIdea host controller"
+	depends on USB_EHCI_HCD
+	select USB_EHCI_ROOT_HUB_TT
+	help
+	  Say Y here to enable host controller functionality of the
+	  ChipIdea driver.
+
+config USB_CHIPIDEA_PCI
+	tristate "Enable PCI glue driver" if EXPERT
+	depends on USB_PCI
+	depends on NOP_USB_XCEIV
+	default USB_CHIPIDEA
+
+config USB_CHIPIDEA_MSM
+	tristate "Enable MSM hsusb glue driver" if EXPERT
+	default USB_CHIPIDEA
+
+config USB_CHIPIDEA_NPCM
+	tristate "Enable NPCM hsusb glue driver" if EXPERT
+	default USB_CHIPIDEA
+
+config USB_CHIPIDEA_IMX
+	tristate "Enable i.MX USB glue driver" if EXPERT
+	depends on OF
+	default USB_CHIPIDEA
+
+config USB_CHIPIDEA_GENERIC
+	tristate "Enable generic USB2 glue driver" if EXPERT
+	default USB_CHIPIDEA
+
+config USB_CHIPIDEA_TEGRA
+	tristate "Enable Tegra USB glue driver" if EXPERT
+	depends on OF
+	default USB_CHIPIDEA
+
+endif