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-a10sr.c | 128 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 128 insertions(+) create mode 100644 drivers/reset/reset-a10sr.c (limited to 'drivers/reset/reset-a10sr.c') diff --git a/drivers/reset/reset-a10sr.c b/drivers/reset/reset-a10sr.c new file mode 100644 index 000000000..99b3bc838 --- /dev/null +++ b/drivers/reset/reset-a10sr.c @@ -0,0 +1,128 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright Intel Corporation (C) 2017. All Rights Reserved + * + * Reset driver for Altera Arria10 MAX5 System Resource Chip + * + * Adapted from reset-socfpga.c + */ + +#include +#include +#include +#include +#include +#include + +#include + +struct a10sr_reset { + struct reset_controller_dev rcdev; + struct regmap *regmap; +}; + +static inline struct a10sr_reset *to_a10sr_rst(struct reset_controller_dev *rc) +{ + return container_of(rc, struct a10sr_reset, rcdev); +} + +static inline int a10sr_reset_shift(unsigned long id) +{ + switch (id) { + case A10SR_RESET_ENET_HPS: + return 1; + case A10SR_RESET_PCIE: + case A10SR_RESET_FILE: + case A10SR_RESET_BQSPI: + case A10SR_RESET_USB: + return id + 11; + default: + return -EINVAL; + } +} + +static int a10sr_reset_update(struct reset_controller_dev *rcdev, + unsigned long id, bool assert) +{ + struct a10sr_reset *a10r = to_a10sr_rst(rcdev); + int offset = a10sr_reset_shift(id); + u8 mask = ALTR_A10SR_REG_BIT_MASK(offset); + int index = ALTR_A10SR_HPS_RST_REG + ALTR_A10SR_REG_OFFSET(offset); + + return regmap_update_bits(a10r->regmap, index, mask, assert ? 0 : mask); +} + +static int a10sr_reset_assert(struct reset_controller_dev *rcdev, + unsigned long id) +{ + return a10sr_reset_update(rcdev, id, true); +} + +static int a10sr_reset_deassert(struct reset_controller_dev *rcdev, + unsigned long id) +{ + return a10sr_reset_update(rcdev, id, false); +} + +static int a10sr_reset_status(struct reset_controller_dev *rcdev, + unsigned long id) +{ + int ret; + struct a10sr_reset *a10r = to_a10sr_rst(rcdev); + int offset = a10sr_reset_shift(id); + u8 mask = ALTR_A10SR_REG_BIT_MASK(offset); + int index = ALTR_A10SR_HPS_RST_REG + ALTR_A10SR_REG_OFFSET(offset); + unsigned int value; + + ret = regmap_read(a10r->regmap, index, &value); + if (ret < 0) + return ret; + + return !!(value & mask); +} + +static const struct reset_control_ops a10sr_reset_ops = { + .assert = a10sr_reset_assert, + .deassert = a10sr_reset_deassert, + .status = a10sr_reset_status, +}; + +static int a10sr_reset_probe(struct platform_device *pdev) +{ + struct altr_a10sr *a10sr = dev_get_drvdata(pdev->dev.parent); + struct a10sr_reset *a10r; + + a10r = devm_kzalloc(&pdev->dev, sizeof(struct a10sr_reset), + GFP_KERNEL); + if (!a10r) + return -ENOMEM; + + a10r->rcdev.owner = THIS_MODULE; + a10r->rcdev.nr_resets = A10SR_RESET_NUM; + a10r->rcdev.ops = &a10sr_reset_ops; + a10r->rcdev.of_node = pdev->dev.of_node; + a10r->regmap = a10sr->regmap; + + platform_set_drvdata(pdev, a10r); + + return devm_reset_controller_register(&pdev->dev, &a10r->rcdev); +} + +static const struct of_device_id a10sr_reset_of_match[] = { + { .compatible = "altr,a10sr-reset" }, + { }, +}; +MODULE_DEVICE_TABLE(of, a10sr_reset_of_match); + +static struct platform_driver a10sr_reset_driver = { + .probe = a10sr_reset_probe, + .driver = { + .name = "altr_a10sr_reset", + .of_match_table = a10sr_reset_of_match, + }, +}; +module_platform_driver(a10sr_reset_driver); + +MODULE_AUTHOR("Thor Thayer "); +MODULE_DESCRIPTION("Altera Arria10 System Resource Reset Controller Driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1