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/touchscreen/ad7879-i2c.c | 74 ++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 drivers/input/touchscreen/ad7879-i2c.c (limited to 'drivers/input/touchscreen/ad7879-i2c.c') diff --git a/drivers/input/touchscreen/ad7879-i2c.c b/drivers/input/touchscreen/ad7879-i2c.c new file mode 100644 index 000000000..c1ccdf86b --- /dev/null +++ b/drivers/input/touchscreen/ad7879-i2c.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * AD7879-1/AD7889-1 touchscreen (I2C bus) + * + * Copyright (C) 2008-2010 Michael Hennerich, Analog Devices Inc. + */ + +#include /* BUS_I2C */ +#include +#include +#include +#include +#include +#include + +#include "ad7879.h" + +#define AD7879_DEVID 0x79 /* AD7879-1/AD7889-1 */ + +static const struct regmap_config ad7879_i2c_regmap_config = { + .reg_bits = 8, + .val_bits = 16, + .max_register = 15, +}; + +static int ad7879_i2c_probe(struct i2c_client *client) +{ + struct regmap *regmap; + + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WORD_DATA)) { + dev_err(&client->dev, "SMBUS Word Data not Supported\n"); + return -EIO; + } + + regmap = devm_regmap_init_i2c(client, &ad7879_i2c_regmap_config); + if (IS_ERR(regmap)) + return PTR_ERR(regmap); + + return ad7879_probe(&client->dev, regmap, client->irq, + BUS_I2C, AD7879_DEVID); +} + +static const struct i2c_device_id ad7879_id[] = { + { .name = "ad7879" }, + { .name = "ad7889" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, ad7879_id); + +#ifdef CONFIG_OF +static const struct of_device_id ad7879_i2c_dt_ids[] = { + { .compatible = "adi,ad7879-1", }, + { } +}; +MODULE_DEVICE_TABLE(of, ad7879_i2c_dt_ids); +#endif + +static struct i2c_driver ad7879_i2c_driver = { + .driver = { + .name = "ad7879", + .dev_groups = ad7879_groups, + .pm = &ad7879_pm_ops, + .of_match_table = of_match_ptr(ad7879_i2c_dt_ids), + }, + .probe = ad7879_i2c_probe, + .id_table = ad7879_id, +}; + +module_i2c_driver(ad7879_i2c_driver); + +MODULE_AUTHOR("Michael Hennerich "); +MODULE_DESCRIPTION("AD7879(-1) touchscreen I2C bus driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1