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, 65 insertions, 0 deletions

diff --git a/drivers/usb/serial/Makefile b/drivers/usb/serial/Makefile
new file mode 100644
index 000000000..c7bb1a881
--- /dev/null
+++ b/drivers/usb/serial/Makefile
@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the USB serial device drivers.
+#
+
+# Object file lists.
+
+obj-$(CONFIG_USB_SERIAL)			+= usbserial.o
+
+usbserial-y := usb-serial.o generic.o bus.o
+
+usbserial-$(CONFIG_USB_SERIAL_CONSOLE)	+= console.o
+
+obj-$(CONFIG_USB_SERIAL_AIRCABLE)		+= aircable.o
+obj-$(CONFIG_USB_SERIAL_ARK3116)		+= ark3116.o
+obj-$(CONFIG_USB_SERIAL_BELKIN)			+= belkin_sa.o
+obj-$(CONFIG_USB_SERIAL_CH341)			+= ch341.o
+obj-$(CONFIG_USB_SERIAL_CP210X)			+= cp210x.o
+obj-$(CONFIG_USB_SERIAL_CYBERJACK)		+= cyberjack.o
+obj-$(CONFIG_USB_SERIAL_CYPRESS_M8)		+= cypress_m8.o
+obj-$(CONFIG_USB_SERIAL_DEBUG)			+= usb_debug.o
+obj-$(CONFIG_USB_SERIAL_DIGI_ACCELEPORT)	+= digi_acceleport.o
+obj-$(CONFIG_USB_SERIAL_EDGEPORT)		+= io_edgeport.o
+obj-$(CONFIG_USB_SERIAL_EDGEPORT_TI)		+= io_ti.o
+obj-$(CONFIG_USB_SERIAL_EMPEG)			+= empeg.o
+obj-$(CONFIG_USB_SERIAL_F81232)			+= f81232.o
+obj-$(CONFIG_USB_SERIAL_F8153X)			+= f81534.o
+obj-$(CONFIG_USB_SERIAL_FTDI_SIO)		+= ftdi_sio.o
+obj-$(CONFIG_USB_SERIAL_GARMIN)			+= garmin_gps.o
+obj-$(CONFIG_USB_SERIAL_IPAQ)			+= ipaq.o
+obj-$(CONFIG_USB_SERIAL_IPW)			+= ipw.o
+obj-$(CONFIG_USB_SERIAL_IR)			+= ir-usb.o
+obj-$(CONFIG_USB_SERIAL_IUU)			+= iuu_phoenix.o
+obj-$(CONFIG_USB_SERIAL_KEYSPAN)		+= keyspan.o
+obj-$(CONFIG_USB_SERIAL_KEYSPAN_PDA)		+= keyspan_pda.o
+obj-$(CONFIG_USB_SERIAL_KLSI)			+= kl5kusb105.o
+obj-$(CONFIG_USB_SERIAL_KOBIL_SCT)		+= kobil_sct.o
+obj-$(CONFIG_USB_SERIAL_MCT_U232)		+= mct_u232.o
+obj-$(CONFIG_USB_SERIAL_METRO)			+= metro-usb.o
+obj-$(CONFIG_USB_SERIAL_MOS7720)		+= mos7720.o
+obj-$(CONFIG_USB_SERIAL_MOS7840)		+= mos7840.o
+obj-$(CONFIG_USB_SERIAL_MXUPORT)		+= mxuport.o
+obj-$(CONFIG_USB_SERIAL_NAVMAN)			+= navman.o
+obj-$(CONFIG_USB_SERIAL_OMNINET)		+= omninet.o
+obj-$(CONFIG_USB_SERIAL_OPTICON)		+= opticon.o
+obj-$(CONFIG_USB_SERIAL_OPTION)			+= option.o
+obj-$(CONFIG_USB_SERIAL_OTI6858)		+= oti6858.o
+obj-$(CONFIG_USB_SERIAL_PL2303)			+= pl2303.o
+obj-$(CONFIG_USB_SERIAL_QCAUX)			+= qcaux.o
+obj-$(CONFIG_USB_SERIAL_QUALCOMM)		+= qcserial.o
+obj-$(CONFIG_USB_SERIAL_QT2)			+= quatech2.o
+obj-$(CONFIG_USB_SERIAL_SAFE)			+= safe_serial.o
+obj-$(CONFIG_USB_SERIAL_SIERRAWIRELESS)		+= sierra.o
+obj-$(CONFIG_USB_SERIAL_SIMPLE)			+= usb-serial-simple.o
+obj-$(CONFIG_USB_SERIAL_SPCP8X5)		+= spcp8x5.o
+obj-$(CONFIG_USB_SERIAL_SSU100)			+= ssu100.o
+obj-$(CONFIG_USB_SERIAL_SYMBOL)			+= symbolserial.o
+obj-$(CONFIG_USB_SERIAL_WWAN)			+= usb_wwan.o
+obj-$(CONFIG_USB_SERIAL_TI)			+= ti_usb_3410_5052.o
+obj-$(CONFIG_USB_SERIAL_UPD78F0730)		+= upd78f0730.o
+obj-$(CONFIG_USB_SERIAL_VISOR)			+= visor.o
+obj-$(CONFIG_USB_SERIAL_WISHBONE)		+= wishbone-serial.o
+obj-$(CONFIG_USB_SERIAL_WHITEHEAT)		+= whiteheat.o
+obj-$(CONFIG_USB_SERIAL_XR)			+= xr_serial.o
+obj-$(CONFIG_USB_SERIAL_XSENS_MT)		+= xsens_mt.o