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, 113 insertions, 0 deletions

diff --git a/scripts/const_structs.checkpatch b/scripts/const_structs.checkpatch
new file mode 100644
index 000000000..6eb94fddc
--- /dev/null
+++ b/scripts/const_structs.checkpatch
@@ -0,0 +1,113 @@
+acpi_dock_ops
+address_space_operations
+backlight_ops
+bin_attribute
+block_device_operations
+bus_type
+clk_ops
+comedi_lrange
+component_ops
+ctl_table
+dentry_operations
+dev_pm_ops
+device_type
+dma_map_ops
+driver_info
+drm_connector_funcs
+drm_encoder_funcs
+drm_encoder_helper_funcs
+dvb_frontend_ops
+dvb_tuner_ops
+ethtool_ops
+extent_io_ops
+fb_ops
+file_lock_operations
+file_operations
+hv_ops
+hwmon_ops
+ib_device_ops
+ide_dma_ops
+ide_port_ops
+ieee80211_ops
+iio_buffer_setup_ops
+inode_operations
+intel_dvo_dev_ops
+irq_domain_ops
+item_operations
+iwl_cfg
+iwl_ops
+kernel_param_ops
+kgdb_arch
+kgdb_io
+kobj_type
+kset_uevent_ops
+lcd_ops
+lock_manager_operations
+machine_desc
+microcode_ops
+mlxsw_reg_info
+mtd_ooblayout_ops
+mtrr_ops
+nand_controller_ops
+neigh_ops
+net_device_ops
+nft_expr_ops
+nlmsvc_binding
+nvkm_device_chip
+of_device_id
+pci_raw_ops
+phy_ops
+pinconf_ops
+pinctrl_ops
+pinmux_ops
+pipe_buf_operations
+platform_hibernation_ops
+platform_suspend_ops
+proc_ops
+proto_ops
+pwm_ops
+reg_default
+reg_field
+reg_sequence
+regmap_access_table
+regmap_bus
+regmap_config
+regmap_irq
+regmap_irq_chip
+regmap_irq_sub_irq_map
+regmap_range
+regmap_range_cfg
+regulator_ops
+reset_control_ops
+rpc_pipe_ops
+rtc_class_ops
+sd_desc
+sdhci_ops
+seq_operations
+sirfsoc_padmux
+snd_ac97_build_ops
+snd_pcm_ops
+snd_rawmidi_ops
+snd_soc_component_driver
+snd_soc_dai_ops
+snd_soc_ops
+snd_soc_tplg_ops
+soc_pcmcia_socket_ops
+stacktrace_ops
+sysfs_ops
+tty_operations
+uart_ops
+usb_mon_operations
+v4l2_ctrl_ops
+v4l2_ioctl_ops
+v4l2_subdev_core_ops
+v4l2_subdev_internal_ops
+v4l2_subdev_ops
+v4l2_subdev_pad_ops
+v4l2_subdev_video_ops
+vb2_ops
+vm_operations_struct
+wacom_features
+watchdog_ops
+wd_ops
+xattr_handler