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-bcm6345.c | 133 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 drivers/reset/reset-bcm6345.c (limited to 'drivers/reset/reset-bcm6345.c') diff --git a/drivers/reset/reset-bcm6345.c b/drivers/reset/reset-bcm6345.c new file mode 100644 index 000000000..441d9dd76 --- /dev/null +++ b/drivers/reset/reset-bcm6345.c @@ -0,0 +1,133 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * BCM6345 Reset Controller Driver + * + * Copyright (C) 2020 Álvaro Fernández Rojas + */ + +#include +#include +#include +#include +#include + +#define BCM6345_RESET_NUM 32 +#define BCM6345_RESET_SLEEP_MIN_US 10000 +#define BCM6345_RESET_SLEEP_MAX_US 20000 + +struct bcm6345_reset { + struct reset_controller_dev rcdev; + void __iomem *base; + spinlock_t lock; +}; + +static inline struct bcm6345_reset * +to_bcm6345_reset(struct reset_controller_dev *rcdev) +{ + return container_of(rcdev, struct bcm6345_reset, rcdev); +} + +static int bcm6345_reset_update(struct reset_controller_dev *rcdev, + unsigned long id, bool assert) +{ + struct bcm6345_reset *bcm6345_reset = to_bcm6345_reset(rcdev); + unsigned long flags; + uint32_t val; + + spin_lock_irqsave(&bcm6345_reset->lock, flags); + val = __raw_readl(bcm6345_reset->base); + if (assert) + val &= ~BIT(id); + else + val |= BIT(id); + __raw_writel(val, bcm6345_reset->base); + spin_unlock_irqrestore(&bcm6345_reset->lock, flags); + + return 0; +} + +static int bcm6345_reset_assert(struct reset_controller_dev *rcdev, + unsigned long id) +{ + return bcm6345_reset_update(rcdev, id, true); +} + +static int bcm6345_reset_deassert(struct reset_controller_dev *rcdev, + unsigned long id) +{ + return bcm6345_reset_update(rcdev, id, false); +} + +static int bcm6345_reset_reset(struct reset_controller_dev *rcdev, + unsigned long id) +{ + bcm6345_reset_update(rcdev, id, true); + usleep_range(BCM6345_RESET_SLEEP_MIN_US, + BCM6345_RESET_SLEEP_MAX_US); + + bcm6345_reset_update(rcdev, id, false); + /* + * Ensure component is taken out reset state by sleeping also after + * deasserting the reset. Otherwise, the component may not be ready + * for operation. + */ + usleep_range(BCM6345_RESET_SLEEP_MIN_US, + BCM6345_RESET_SLEEP_MAX_US); + + return 0; +} + +static int bcm6345_reset_status(struct reset_controller_dev *rcdev, + unsigned long id) +{ + struct bcm6345_reset *bcm6345_reset = to_bcm6345_reset(rcdev); + + return !(__raw_readl(bcm6345_reset->base) & BIT(id)); +} + +static const struct reset_control_ops bcm6345_reset_ops = { + .assert = bcm6345_reset_assert, + .deassert = bcm6345_reset_deassert, + .reset = bcm6345_reset_reset, + .status = bcm6345_reset_status, +}; + +static int bcm6345_reset_probe(struct platform_device *pdev) +{ + struct bcm6345_reset *bcm6345_reset; + + bcm6345_reset = devm_kzalloc(&pdev->dev, + sizeof(*bcm6345_reset), GFP_KERNEL); + if (!bcm6345_reset) + return -ENOMEM; + + bcm6345_reset->base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(bcm6345_reset->base)) + return PTR_ERR(bcm6345_reset->base); + + spin_lock_init(&bcm6345_reset->lock); + bcm6345_reset->rcdev.ops = &bcm6345_reset_ops; + bcm6345_reset->rcdev.owner = THIS_MODULE; + bcm6345_reset->rcdev.of_node = pdev->dev.of_node; + bcm6345_reset->rcdev.of_reset_n_cells = 1; + bcm6345_reset->rcdev.nr_resets = BCM6345_RESET_NUM; + + return devm_reset_controller_register(&pdev->dev, + &bcm6345_reset->rcdev); +} + +static const struct of_device_id bcm6345_reset_of_match[] = { + { .compatible = "brcm,bcm6345-reset" }, + { .compatible = "brcm,bcm63xx-ephy-ctrl" }, + { /* sentinel */ }, +}; + +static struct platform_driver bcm6345_reset_driver = { + .probe = bcm6345_reset_probe, + .driver = { + .name = "bcm6345-reset", + .of_match_table = bcm6345_reset_of_match, + .suppress_bind_attrs = true, + }, +}; +builtin_platform_driver(bcm6345_reset_driver); -- cgit v1.3.1