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 --- drivers/acpi/tiny-power-button.c | 87 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100644 drivers/acpi/tiny-power-button.c (limited to 'drivers/acpi/tiny-power-button.c') diff --git a/drivers/acpi/tiny-power-button.c b/drivers/acpi/tiny-power-button.c new file mode 100644 index 000000000..92516ef84 --- /dev/null +++ b/drivers/acpi/tiny-power-button.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +#include +#include +#include +#include +#include + +MODULE_AUTHOR("Josh Triplett"); +MODULE_DESCRIPTION("ACPI Tiny Power Button Driver"); +MODULE_LICENSE("GPL"); + +static int power_signal __read_mostly = CONFIG_ACPI_TINY_POWER_BUTTON_SIGNAL; +module_param(power_signal, int, 0644); +MODULE_PARM_DESC(power_signal, "Power button sends this signal to init"); + +static const struct acpi_device_id tiny_power_button_device_ids[] = { + { ACPI_BUTTON_HID_POWER, 0 }, + { ACPI_BUTTON_HID_POWERF, 0 }, + { "", 0 }, +}; +MODULE_DEVICE_TABLE(acpi, tiny_power_button_device_ids); + +static void acpi_tiny_power_button_notify(acpi_handle handle, u32 event, void *data) +{ + kill_cad_pid(power_signal, 1); +} + +static void acpi_tiny_power_button_notify_run(void *not_used) +{ + acpi_tiny_power_button_notify(NULL, ACPI_FIXED_HARDWARE_EVENT, NULL); +} + +static u32 acpi_tiny_power_button_event(void *not_used) +{ + acpi_os_execute(OSL_NOTIFY_HANDLER, acpi_tiny_power_button_notify_run, NULL); + return ACPI_INTERRUPT_HANDLED; +} + +static int acpi_tiny_power_button_probe(struct platform_device *pdev) +{ + struct acpi_device *device; + acpi_status status; + + device = ACPI_COMPANION(&pdev->dev); + if (!device) + return -ENODEV; + + if (device->device_type == ACPI_BUS_TYPE_POWER_BUTTON) { + status = acpi_install_fixed_event_handler(ACPI_EVENT_POWER_BUTTON, + acpi_tiny_power_button_event, + NULL); + } else { + status = acpi_install_notify_handler(device->handle, + ACPI_DEVICE_NOTIFY, + acpi_tiny_power_button_notify, + NULL); + } + if (ACPI_FAILURE(status)) + return -ENODEV; + + return 0; +} + +static void acpi_tiny_power_button_remove(struct platform_device *pdev) +{ + struct acpi_device *device = ACPI_COMPANION(&pdev->dev); + + if (device->device_type == ACPI_BUS_TYPE_POWER_BUTTON) { + acpi_remove_fixed_event_handler(ACPI_EVENT_POWER_BUTTON, + acpi_tiny_power_button_event); + } else { + acpi_remove_notify_handler(device->handle, ACPI_DEVICE_NOTIFY, + acpi_tiny_power_button_notify); + } + acpi_os_wait_events_complete(); +} + +static struct platform_driver acpi_tiny_power_button_driver = { + .probe = acpi_tiny_power_button_probe, + .remove = acpi_tiny_power_button_remove, + .driver = { + .name = "acpi-tiny-power-button", + .acpi_match_table = tiny_power_button_device_ids, + }, +}; + +module_platform_driver(acpi_tiny_power_button_driver); -- cgit v1.3.1