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/atmel-flexcom.c | 123 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 drivers/mfd/atmel-flexcom.c (limited to 'drivers/mfd/atmel-flexcom.c') diff --git a/drivers/mfd/atmel-flexcom.c b/drivers/mfd/atmel-flexcom.c new file mode 100644 index 000000000..d5df5466e --- /dev/null +++ b/drivers/mfd/atmel-flexcom.c @@ -0,0 +1,123 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Driver for Atmel Flexcom + * + * Copyright (C) 2015 Atmel Corporation + * + * Author: Cyrille Pitchen + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* I/O register offsets */ +#define FLEX_MR 0x0 /* Mode Register */ +#define FLEX_VERSION 0xfc /* Version Register */ + +/* Mode Register bit fields */ +#define FLEX_MR_OPMODE_OFFSET (0) /* Operating Mode */ +#define FLEX_MR_OPMODE_MASK (0x3 << FLEX_MR_OPMODE_OFFSET) +#define FLEX_MR_OPMODE(opmode) (((opmode) << FLEX_MR_OPMODE_OFFSET) & \ + FLEX_MR_OPMODE_MASK) + +struct atmel_flexcom { + void __iomem *base; + u32 opmode; + struct clk *clk; +}; + +static int atmel_flexcom_probe(struct platform_device *pdev) +{ + struct device_node *np = pdev->dev.of_node; + struct atmel_flexcom *ddata; + int err; + + ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL); + if (!ddata) + return -ENOMEM; + + platform_set_drvdata(pdev, ddata); + + err = of_property_read_u32(np, "atmel,flexcom-mode", &ddata->opmode); + if (err) + return err; + + if (ddata->opmode < ATMEL_FLEXCOM_MODE_USART || + ddata->opmode > ATMEL_FLEXCOM_MODE_TWI) + return -EINVAL; + + ddata->base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL); + if (IS_ERR(ddata->base)) + return PTR_ERR(ddata->base); + + ddata->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(ddata->clk)) + return PTR_ERR(ddata->clk); + + err = clk_prepare_enable(ddata->clk); + if (err) + return err; + + /* + * Set the Operating Mode in the Mode Register: only the selected device + * is clocked. Hence, registers of the other serial devices remain + * inaccessible and are read as zero. Also the external I/O lines of the + * Flexcom are muxed to reach the selected device. + */ + writel(FLEX_MR_OPMODE(ddata->opmode), ddata->base + FLEX_MR); + + clk_disable_unprepare(ddata->clk); + + return devm_of_platform_populate(&pdev->dev); +} + +static const struct of_device_id atmel_flexcom_of_match[] = { + { .compatible = "atmel,sama5d2-flexcom" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, atmel_flexcom_of_match); + +static int __maybe_unused atmel_flexcom_resume_noirq(struct device *dev) +{ + struct atmel_flexcom *ddata = dev_get_drvdata(dev); + int err; + u32 val; + + err = clk_prepare_enable(ddata->clk); + if (err) + return err; + + val = FLEX_MR_OPMODE(ddata->opmode); + writel(val, ddata->base + FLEX_MR); + + clk_disable_unprepare(ddata->clk); + + return 0; +} + +static const struct dev_pm_ops __maybe_unused atmel_flexcom_pm_ops = { + .resume_noirq = atmel_flexcom_resume_noirq, +}; + +static struct platform_driver atmel_flexcom_driver = { + .probe = atmel_flexcom_probe, + .driver = { + .name = "atmel_flexcom", + .pm = pm_ptr(&atmel_flexcom_pm_ops), + .of_match_table = atmel_flexcom_of_match, + }, +}; + +module_platform_driver(atmel_flexcom_driver); + +MODULE_AUTHOR("Cyrille Pitchen "); +MODULE_DESCRIPTION("Atmel Flexcom MFD driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1