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/input/apm-power.c | 122 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 122 insertions(+) create mode 100644 drivers/input/apm-power.c (limited to 'drivers/input/apm-power.c') diff --git a/drivers/input/apm-power.c b/drivers/input/apm-power.c new file mode 100644 index 000000000..028fcaf4c --- /dev/null +++ b/drivers/input/apm-power.c @@ -0,0 +1,122 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Input Power Event -> APM Bridge + * + * Copyright (c) 2007 Richard Purdie + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include + +static void system_power_event(unsigned int keycode) +{ + switch (keycode) { + case KEY_SUSPEND: + apm_queue_event(APM_USER_SUSPEND); + pr_info("Requesting system suspend...\n"); + break; + default: + break; + } +} + +static void apmpower_event(struct input_handle *handle, unsigned int type, + unsigned int code, int value) +{ + /* only react on key down events */ + if (value != 1) + return; + + switch (type) { + case EV_PWR: + system_power_event(code); + break; + + default: + break; + } +} + +static int apmpower_connect(struct input_handler *handler, + struct input_dev *dev, + const struct input_device_id *id) +{ + struct input_handle *handle; + int error; + + handle = kzalloc_obj(struct input_handle); + if (!handle) + return -ENOMEM; + + handle->dev = dev; + handle->handler = handler; + handle->name = "apm-power"; + + error = input_register_handle(handle); + if (error) { + pr_err("Failed to register input power handler, error %d\n", + error); + kfree(handle); + return error; + } + + error = input_open_device(handle); + if (error) { + pr_err("Failed to open input power device, error %d\n", error); + input_unregister_handle(handle); + kfree(handle); + return error; + } + + return 0; +} + +static void apmpower_disconnect(struct input_handle *handle) +{ + input_close_device(handle); + input_unregister_handle(handle); + kfree(handle); +} + +static const struct input_device_id apmpower_ids[] = { + { + .flags = INPUT_DEVICE_ID_MATCH_EVBIT, + .evbit = { BIT_MASK(EV_PWR) }, + }, + { }, +}; + +MODULE_DEVICE_TABLE(input, apmpower_ids); + +static struct input_handler apmpower_handler = { + .event = apmpower_event, + .connect = apmpower_connect, + .disconnect = apmpower_disconnect, + .name = "apm-power", + .id_table = apmpower_ids, +}; + +static int __init apmpower_init(void) +{ + return input_register_handler(&apmpower_handler); +} + +static void __exit apmpower_exit(void) +{ + input_unregister_handler(&apmpower_handler); +} + +module_init(apmpower_init); +module_exit(apmpower_exit); + +MODULE_AUTHOR("Richard Purdie "); +MODULE_DESCRIPTION("Input Power Event -> APM Bridge"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1