From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug 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 Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- scripts/const_structs.checkpatch | 113 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) create mode 100644 scripts/const_structs.checkpatch (limited to 'scripts/const_structs.checkpatch') 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 -- cgit v1.3.1