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, 37 insertions, 0 deletions

diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
new file mode 100644
index 000000000..048586746
--- /dev/null
+++ b/drivers/net/mdio/Makefile
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for Linux MDIO bus drivers
+
+obj-$(CONFIG_ACPI_MDIO)		+= acpi_mdio.o
+obj-$(CONFIG_FWNODE_MDIO)	+= fwnode_mdio.o
+obj-$(CONFIG_OF_MDIO)		+= of_mdio.o
+
+obj-$(CONFIG_MDIO_AIROHA)		+= mdio-airoha.o
+obj-$(CONFIG_MDIO_ASPEED)		+= mdio-aspeed.o
+obj-$(CONFIG_MDIO_BCM_IPROC)		+= mdio-bcm-iproc.o
+obj-$(CONFIG_MDIO_BCM_UNIMAC)		+= mdio-bcm-unimac.o
+obj-$(CONFIG_MDIO_BITBANG)		+= mdio-bitbang.o
+obj-$(CONFIG_MDIO_CAVIUM)		+= mdio-cavium.o
+obj-$(CONFIG_MDIO_GPIO)			+= mdio-gpio.o
+obj-$(CONFIG_MDIO_HISI_FEMAC)		+= mdio-hisi-femac.o
+obj-$(CONFIG_MDIO_I2C)			+= mdio-i2c.o
+obj-$(CONFIG_MDIO_IPQ4019)		+= mdio-ipq4019.o
+obj-$(CONFIG_MDIO_IPQ8064)		+= mdio-ipq8064.o
+obj-$(CONFIG_MDIO_MOXART)		+= mdio-moxart.o
+obj-$(CONFIG_MDIO_MSCC_MIIM)		+= mdio-mscc-miim.o
+obj-$(CONFIG_MDIO_MVUSB)		+= mdio-mvusb.o
+obj-$(CONFIG_MDIO_OCTEON)		+= mdio-octeon.o
+obj-$(CONFIG_MDIO_PIC64HPSC)		+= mdio-pic64hpsc.o
+obj-$(CONFIG_MDIO_REALTEK_RTL9300)	+= mdio-realtek-rtl9300.o
+obj-$(CONFIG_MDIO_REGMAP)		+= mdio-regmap.o
+obj-$(CONFIG_MDIO_SUN4I)		+= mdio-sun4i.o
+obj-$(CONFIG_MDIO_THUNDER)		+= mdio-thunder.o
+obj-$(CONFIG_MDIO_XGENE)		+= mdio-xgene.o
+
+obj-$(CONFIG_MDIO_BUS_MUX)		+= mdio-mux.o
+obj-$(CONFIG_MDIO_BUS_MUX_BCM6368)	+= mdio-mux-bcm6368.o
+obj-$(CONFIG_MDIO_BUS_MUX_BCM_IPROC)	+= mdio-mux-bcm-iproc.o
+obj-$(CONFIG_MDIO_BUS_MUX_GPIO)		+= mdio-mux-gpio.o
+obj-$(CONFIG_MDIO_BUS_MUX_MESON_G12A)	+= mdio-mux-meson-g12a.o
+obj-$(CONFIG_MDIO_BUS_MUX_MESON_GXL)	+= mdio-mux-meson-gxl.o
+obj-$(CONFIG_MDIO_BUS_MUX_MMIOREG) 	+= mdio-mux-mmioreg.o
+obj-$(CONFIG_MDIO_BUS_MUX_MULTIPLEXER) 	+= mdio-mux-multiplexer.o