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-brcmstb.c | 126 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 126 insertions(+) create mode 100644 drivers/reset/reset-brcmstb.c (limited to 'drivers/reset/reset-brcmstb.c') diff --git a/drivers/reset/reset-brcmstb.c b/drivers/reset/reset-brcmstb.c new file mode 100644 index 000000000..810fe7645 --- /dev/null +++ b/drivers/reset/reset-brcmstb.c @@ -0,0 +1,126 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Broadcom STB generic reset controller for SW_INIT style reset controller + * + * Author: Florian Fainelli + * Copyright (C) 2018 Broadcom + */ +#include +#include +#include +#include +#include +#include +#include +#include + +struct brcmstb_reset { + void __iomem *base; + struct reset_controller_dev rcdev; +}; + +#define SW_INIT_SET 0x00 +#define SW_INIT_CLEAR 0x04 +#define SW_INIT_STATUS 0x08 + +#define SW_INIT_BIT(id) BIT((id) & 0x1f) +#define SW_INIT_BANK(id) ((id) >> 5) + +/* A full bank contains extra registers that we are not utilizing but still + * qualify as a single bank. + */ +#define SW_INIT_BANK_SIZE 0x18 + +static inline +struct brcmstb_reset *to_brcmstb(struct reset_controller_dev *rcdev) +{ + return container_of(rcdev, struct brcmstb_reset, rcdev); +} + +static int brcmstb_reset_assert(struct reset_controller_dev *rcdev, + unsigned long id) +{ + unsigned int off = SW_INIT_BANK(id) * SW_INIT_BANK_SIZE; + struct brcmstb_reset *priv = to_brcmstb(rcdev); + + writel_relaxed(SW_INIT_BIT(id), priv->base + off + SW_INIT_SET); + + return 0; +} + +static int brcmstb_reset_deassert(struct reset_controller_dev *rcdev, + unsigned long id) +{ + unsigned int off = SW_INIT_BANK(id) * SW_INIT_BANK_SIZE; + struct brcmstb_reset *priv = to_brcmstb(rcdev); + + writel_relaxed(SW_INIT_BIT(id), priv->base + off + SW_INIT_CLEAR); + /* Maximum reset delay after de-asserting a line and seeing block + * operation is typically 14us for the worst case, build some slack + * here. + */ + usleep_range(100, 200); + + return 0; +} + +static int brcmstb_reset_status(struct reset_controller_dev *rcdev, + unsigned long id) +{ + unsigned int off = SW_INIT_BANK(id) * SW_INIT_BANK_SIZE; + struct brcmstb_reset *priv = to_brcmstb(rcdev); + + return readl_relaxed(priv->base + off + SW_INIT_STATUS) & + SW_INIT_BIT(id); +} + +static const struct reset_control_ops brcmstb_reset_ops = { + .assert = brcmstb_reset_assert, + .deassert = brcmstb_reset_deassert, + .status = brcmstb_reset_status, +}; + +static int brcmstb_reset_probe(struct platform_device *pdev) +{ + struct device *kdev = &pdev->dev; + struct brcmstb_reset *priv; + struct resource *res; + + priv = devm_kzalloc(kdev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res); + if (IS_ERR(priv->base)) + return PTR_ERR(priv->base); + + dev_set_drvdata(kdev, priv); + + priv->rcdev.owner = THIS_MODULE; + priv->rcdev.nr_resets = DIV_ROUND_DOWN_ULL(resource_size(res), + SW_INIT_BANK_SIZE) * 32; + priv->rcdev.ops = &brcmstb_reset_ops; + priv->rcdev.of_node = kdev->of_node; + /* Use defaults: 1 cell and simple xlate function */ + + return devm_reset_controller_register(kdev, &priv->rcdev); +} + +static const struct of_device_id brcmstb_reset_of_match[] = { + { .compatible = "brcm,brcmstb-reset" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, brcmstb_reset_of_match); + +static struct platform_driver brcmstb_reset_driver = { + .probe = brcmstb_reset_probe, + .driver = { + .name = "brcmstb-reset", + .of_match_table = brcmstb_reset_of_match, + }, +}; +module_platform_driver(brcmstb_reset_driver); + +MODULE_AUTHOR("Broadcom"); +MODULE_DESCRIPTION("Broadcom STB reset controller"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1