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, 88 insertions, 0 deletions

diff --git a/drivers/net/Makefile b/drivers/net/Makefile
new file mode 100644
index 000000000..88e4c485d
--- /dev/null
+++ b/drivers/net/Makefile
@@ -0,0 +1,88 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux network device drivers.
+#
+
+#
+# Networking Core Drivers
+#
+obj-$(CONFIG_BONDING) += bonding/
+obj-$(CONFIG_IPVLAN) += ipvlan/
+obj-$(CONFIG_IPVTAP) += ipvlan/
+obj-$(CONFIG_DUMMY) += dummy.o
+obj-$(CONFIG_WIREGUARD) += wireguard/
+obj-$(CONFIG_OVPN) += ovpn/
+obj-$(CONFIG_EQUALIZER) += eql.o
+obj-$(CONFIG_IFB) += ifb.o
+obj-$(CONFIG_MACSEC) += macsec.o
+obj-$(CONFIG_AMT) += amt.o
+obj-$(CONFIG_MACVLAN) += macvlan.o
+obj-$(CONFIG_MACVTAP) += macvtap.o
+obj-$(CONFIG_MII) += mii.o
+obj-$(CONFIG_MDIO) += mdio.o
+obj-$(CONFIG_NET) += loopback.o
+obj-$(CONFIG_NETCONSOLE) += netconsole.o
+obj-$(CONFIG_NETKIT) += netkit.o
+obj-y += phy/
+obj-y += pse-pd/
+obj-y += mdio/
+obj-y += pcs/
+obj-$(CONFIG_RIONET) += rionet.o
+obj-$(CONFIG_NET_TEAM) += team/
+obj-$(CONFIG_TUN) += tun.o
+obj-$(CONFIG_TAP) += tap.o
+obj-$(CONFIG_VETH) += veth.o
+obj-$(CONFIG_VIRTIO_NET) += virtio_net.o
+obj-$(CONFIG_VXLAN) += vxlan/
+obj-$(CONFIG_GENEVE) += geneve.o
+obj-$(CONFIG_BAREUDP) += bareudp.o
+obj-$(CONFIG_GTP) += gtp.o
+obj-$(CONFIG_NLMON) += nlmon.o
+obj-$(CONFIG_PFCP) += pfcp.o
+obj-$(CONFIG_NET_VRF) += vrf.o
+obj-$(CONFIG_VSOCKMON) += vsockmon.o
+obj-$(CONFIG_MHI_NET) += mhi_net.o
+
+#
+# Networking Drivers
+#
+obj-$(CONFIG_ARCNET) += arcnet/
+obj-$(CONFIG_CAN) += can/
+ifdef CONFIG_NET_DSA
+obj-y += dsa/
+endif
+obj-$(CONFIG_ETHERNET) += ethernet/
+obj-$(CONFIG_FDDI) += fddi/
+obj-$(CONFIG_QCOM_IPA) += ipa/
+obj-$(CONFIG_PLIP) += plip/
+obj-$(CONFIG_PPP) += ppp/
+obj-$(CONFIG_PPP_ASYNC) += ppp/
+obj-$(CONFIG_PPP_BSDCOMP) += ppp/
+obj-$(CONFIG_PPP_DEFLATE) += ppp/
+obj-$(CONFIG_PPP_MPPE) += ppp/
+obj-$(CONFIG_PPP_SYNC_TTY) += ppp/
+obj-$(CONFIG_PPPOE) += ppp/
+obj-$(CONFIG_PPPOL2TP) += ppp/
+obj-$(CONFIG_PPTP) += ppp/
+obj-$(CONFIG_SLIP) += slip/
+obj-$(CONFIG_SLHC) += slip/
+obj-$(CONFIG_SUNGEM_PHY) += sungem_phy.o
+obj-$(CONFIG_WAN) += wan/
+obj-$(CONFIG_WLAN) += wireless/
+obj-$(CONFIG_IEEE802154) += ieee802154/
+obj-$(CONFIG_WWAN) += wwan/
+obj-$(CONFIG_MCTP) += mctp/
+
+obj-$(CONFIG_VMXNET3) += vmxnet3/
+obj-$(CONFIG_XEN_NETDEV_FRONTEND) += xen-netfront.o
+obj-$(CONFIG_XEN_NETDEV_BACKEND) += xen-netback/
+
+obj-$(CONFIG_USB_NET_DRIVERS) += usb/
+
+obj-$(CONFIG_HYPERV_NET) += hyperv/
+obj-$(CONFIG_NTB_NETDEV) += ntb_netdev.o
+
+obj-$(CONFIG_FUJITSU_ES) += fjes/
+obj-$(CONFIG_USB4_NET) += thunderbolt/
+obj-$(CONFIG_NETDEVSIM) += netdevsim/
+obj-$(CONFIG_NET_FAILOVER) += net_failover.o