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/mfd/act8945a.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 drivers/mfd/act8945a.c (limited to 'drivers/mfd/act8945a.c') diff --git a/drivers/mfd/act8945a.c b/drivers/mfd/act8945a.c new file mode 100644 index 000000000..cafefb445 --- /dev/null +++ b/drivers/mfd/act8945a.c @@ -0,0 +1,91 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * MFD driver for Active-semi ACT8945a PMIC + * + * Copyright (C) 2015 Atmel Corporation. + * + * Author: Wenyou Yang + */ + +#include +#include +#include +#include +#include + +static const struct mfd_cell act8945a_devs[] = { + { + .name = "act8945a-regulator", + }, + { + .name = "act8945a-charger", + .of_compatible = "active-semi,act8945a-charger", + }, +}; + +static const struct regmap_config act8945a_regmap_config = { + .reg_bits = 8, + .val_bits = 8, +}; + +static int act8945a_i2c_probe(struct i2c_client *i2c) +{ + int ret; + struct regmap *regmap; + + regmap = devm_regmap_init_i2c(i2c, &act8945a_regmap_config); + if (IS_ERR(regmap)) { + ret = PTR_ERR(regmap); + dev_err(&i2c->dev, "regmap init failed: %d\n", ret); + return ret; + } + + i2c_set_clientdata(i2c, regmap); + + ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_NONE, + act8945a_devs, ARRAY_SIZE(act8945a_devs), + NULL, 0, NULL); + if (ret) { + dev_err(&i2c->dev, "Failed to add sub devices\n"); + return ret; + } + + return 0; +} + +static const struct i2c_device_id act8945a_i2c_id[] = { + { "act8945a" }, + {} +}; +MODULE_DEVICE_TABLE(i2c, act8945a_i2c_id); + +static const struct of_device_id act8945a_of_match[] = { + { .compatible = "active-semi,act8945a", }, + {}, +}; +MODULE_DEVICE_TABLE(of, act8945a_of_match); + +static struct i2c_driver act8945a_i2c_driver = { + .driver = { + .name = "act8945a", + .of_match_table = act8945a_of_match, + }, + .probe = act8945a_i2c_probe, + .id_table = act8945a_i2c_id, +}; + +static int __init act8945a_i2c_init(void) +{ + return i2c_add_driver(&act8945a_i2c_driver); +} +subsys_initcall(act8945a_i2c_init); + +static void __exit act8945a_i2c_exit(void) +{ + i2c_del_driver(&act8945a_i2c_driver); +} +module_exit(act8945a_i2c_exit); + +MODULE_DESCRIPTION("ACT8945A PMIC multi-function driver"); +MODULE_AUTHOR("Wenyou Yang "); +MODULE_LICENSE("GPL"); -- cgit v1.3.1