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/reset/reset-berlin.c | 111 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 drivers/reset/reset-berlin.c (limited to 'drivers/reset/reset-berlin.c') diff --git a/drivers/reset/reset-berlin.c b/drivers/reset/reset-berlin.c new file mode 100644 index 000000000..578fe8670 --- /dev/null +++ b/drivers/reset/reset-berlin.c @@ -0,0 +1,111 @@ +/* + * Copyright (C) 2014 Marvell Technology Group Ltd. + * + * Marvell Berlin reset driver + * + * Antoine Tenart + * Sebastian Hesselbarth + * + * This file is licensed under the terms of the GNU General Public + * License version 2. This program is licensed "as is" without any + * warranty of any kind, whether express or implied. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define BERLIN_MAX_RESETS 32 + +#define to_berlin_reset_priv(p) \ + container_of((p), struct berlin_reset_priv, rcdev) + +struct berlin_reset_priv { + struct regmap *regmap; + struct reset_controller_dev rcdev; +}; + +static int berlin_reset_reset(struct reset_controller_dev *rcdev, + unsigned long id) +{ + struct berlin_reset_priv *priv = to_berlin_reset_priv(rcdev); + int offset = id >> 8; + int mask = BIT(id & 0x1f); + + regmap_write(priv->regmap, offset, mask); + + /* let the reset be effective */ + udelay(10); + + return 0; +} + +static const struct reset_control_ops berlin_reset_ops = { + .reset = berlin_reset_reset, +}; + +static int berlin_reset_xlate(struct reset_controller_dev *rcdev, + const struct of_phandle_args *reset_spec) +{ + unsigned int offset, bit; + + offset = reset_spec->args[0]; + bit = reset_spec->args[1]; + + if (bit >= BERLIN_MAX_RESETS) + return -EINVAL; + + return (offset << 8) | bit; +} + +static int berlin2_reset_probe(struct platform_device *pdev) +{ + struct device_node *parent_np; + struct berlin_reset_priv *priv; + + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + parent_np = of_get_parent(pdev->dev.of_node); + priv->regmap = syscon_node_to_regmap(parent_np); + of_node_put(parent_np); + if (IS_ERR(priv->regmap)) + return PTR_ERR(priv->regmap); + + priv->rcdev.owner = THIS_MODULE; + priv->rcdev.ops = &berlin_reset_ops; + priv->rcdev.of_node = pdev->dev.of_node; + priv->rcdev.of_reset_n_cells = 2; + priv->rcdev.of_xlate = berlin_reset_xlate; + + return reset_controller_register(&priv->rcdev); +} + +static const struct of_device_id berlin_reset_dt_match[] = { + { .compatible = "marvell,berlin2-reset" }, + { }, +}; +MODULE_DEVICE_TABLE(of, berlin_reset_dt_match); + +static struct platform_driver berlin_reset_driver = { + .probe = berlin2_reset_probe, + .driver = { + .name = "berlin2-reset", + .of_match_table = berlin_reset_dt_match, + }, +}; +module_platform_driver(berlin_reset_driver); + +MODULE_AUTHOR("Antoine Tenart "); +MODULE_AUTHOR("Sebastian Hesselbarth "); +MODULE_DESCRIPTION("Synaptics Berlin reset controller"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1