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-gpio.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 drivers/reset/reset-gpio.c (limited to 'drivers/reset/reset-gpio.c') diff --git a/drivers/reset/reset-gpio.c b/drivers/reset/reset-gpio.c new file mode 100644 index 000000000..bf95296a5 --- /dev/null +++ b/drivers/reset/reset-gpio.c @@ -0,0 +1,99 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include + +struct reset_gpio_priv { + struct reset_controller_dev rc; + struct gpio_desc *reset; +}; + +static inline struct reset_gpio_priv +*rc_to_reset_gpio(struct reset_controller_dev *rc) +{ + return container_of(rc, struct reset_gpio_priv, rc); +} + +static int reset_gpio_assert(struct reset_controller_dev *rc, unsigned long id) +{ + struct reset_gpio_priv *priv = rc_to_reset_gpio(rc); + + return gpiod_set_value_cansleep(priv->reset, 1); +} + +static int reset_gpio_deassert(struct reset_controller_dev *rc, + unsigned long id) +{ + struct reset_gpio_priv *priv = rc_to_reset_gpio(rc); + + return gpiod_set_value_cansleep(priv->reset, 0); +} + +static int reset_gpio_status(struct reset_controller_dev *rc, unsigned long id) +{ + struct reset_gpio_priv *priv = rc_to_reset_gpio(rc); + + return gpiod_get_value_cansleep(priv->reset); +} + +static const struct reset_control_ops reset_gpio_ops = { + .assert = reset_gpio_assert, + .deassert = reset_gpio_deassert, + .status = reset_gpio_status, +}; + +static int reset_gpio_fwnode_xlate(struct reset_controller_dev *rcdev, + const struct fwnode_reference_args *reset_spec) +{ + return reset_spec->args[0]; +} + +static int reset_gpio_probe(struct auxiliary_device *adev, + const struct auxiliary_device_id *id) +{ + struct device *dev = &adev->dev; + struct reset_gpio_priv *priv; + + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH); + if (IS_ERR(priv->reset)) + return dev_err_probe(dev, PTR_ERR(priv->reset), + "Could not get reset gpios\n"); + + priv->rc.ops = &reset_gpio_ops; + priv->rc.owner = THIS_MODULE; + priv->rc.dev = dev; + + /* Cells to match GPIO specifier, but it's not really used */ + priv->rc.fwnode_reset_n_cells = 2; + priv->rc.fwnode_xlate = reset_gpio_fwnode_xlate; + priv->rc.nr_resets = 1; + + return devm_reset_controller_register(dev, &priv->rc); +} + +static const struct auxiliary_device_id reset_gpio_ids[] = { + { .name = "reset.gpio" }, + {} +}; +MODULE_DEVICE_TABLE(auxiliary, reset_gpio_ids); + +static struct auxiliary_driver reset_gpio_driver = { + .probe = reset_gpio_probe, + .id_table = reset_gpio_ids, + .driver = { + .name = "reset-gpio", + .suppress_bind_attrs = true, + }, +}; +module_auxiliary_driver(reset_gpio_driver); + +MODULE_AUTHOR("Krzysztof Kozlowski "); +MODULE_DESCRIPTION("Generic GPIO reset driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1