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/input/input-poller.c | 221 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 221 insertions(+) create mode 100644 drivers/input/input-poller.c (limited to 'drivers/input/input-poller.c') diff --git a/drivers/input/input-poller.c b/drivers/input/input-poller.c new file mode 100644 index 000000000..54dc07fca --- /dev/null +++ b/drivers/input/input-poller.c @@ -0,0 +1,221 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Support for polling mode for input devices. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include "input-poller.h" + +struct input_dev_poller { + void (*poll)(struct input_dev *dev); + + unsigned int poll_interval; /* msec */ + unsigned int poll_interval_max; /* msec */ + unsigned int poll_interval_min; /* msec */ + + struct input_dev *input; + struct delayed_work work; +}; + +static void input_dev_poller_queue_work(struct input_dev_poller *poller) +{ + unsigned long delay; + + delay = msecs_to_jiffies(poller->poll_interval); + if (delay >= HZ) + delay = round_jiffies_relative(delay); + + queue_delayed_work(system_freezable_wq, &poller->work, delay); +} + +static void input_dev_poller_work(struct work_struct *work) +{ + struct input_dev_poller *poller = + container_of(work, struct input_dev_poller, work.work); + + poller->poll(poller->input); + input_dev_poller_queue_work(poller); +} + +void input_dev_poller_finalize(struct input_dev_poller *poller) +{ + if (!poller->poll_interval) + poller->poll_interval = 500; + if (!poller->poll_interval_max) + poller->poll_interval_max = poller->poll_interval; +} + +void input_dev_poller_start(struct input_dev_poller *poller) +{ + /* Only start polling if polling is enabled */ + if (poller->poll_interval > 0) { + poller->poll(poller->input); + input_dev_poller_queue_work(poller); + } +} + +void input_dev_poller_stop(struct input_dev_poller *poller) +{ + cancel_delayed_work_sync(&poller->work); +} + +int input_setup_polling(struct input_dev *dev, + void (*poll_fn)(struct input_dev *dev)) +{ + struct input_dev_poller *poller; + + poller = kzalloc_obj(*poller); + if (!poller) { + /* + * We want to show message even though kzalloc() may have + * printed backtrace as knowing what instance of input + * device we were dealing with is helpful. + */ + dev_err(dev->dev.parent ?: &dev->dev, + "%s: unable to allocate poller structure\n", __func__); + return -ENOMEM; + } + + INIT_DELAYED_WORK(&poller->work, input_dev_poller_work); + poller->input = dev; + poller->poll = poll_fn; + + dev->poller = poller; + return 0; +} +EXPORT_SYMBOL(input_setup_polling); + +static bool input_dev_ensure_poller(struct input_dev *dev) +{ + if (!dev->poller) { + dev_err(dev->dev.parent ?: &dev->dev, + "poller structure has not been set up\n"); + return false; + } + + return true; +} + +void input_set_poll_interval(struct input_dev *dev, unsigned int interval) +{ + if (input_dev_ensure_poller(dev)) + dev->poller->poll_interval = interval; +} +EXPORT_SYMBOL(input_set_poll_interval); + +void input_set_min_poll_interval(struct input_dev *dev, unsigned int interval) +{ + if (input_dev_ensure_poller(dev)) + dev->poller->poll_interval_min = interval; +} +EXPORT_SYMBOL(input_set_min_poll_interval); + +void input_set_max_poll_interval(struct input_dev *dev, unsigned int interval) +{ + if (input_dev_ensure_poller(dev)) + dev->poller->poll_interval_max = interval; +} +EXPORT_SYMBOL(input_set_max_poll_interval); + +int input_get_poll_interval(struct input_dev *dev) +{ + if (!dev->poller) + return -EINVAL; + + return dev->poller->poll_interval; +} +EXPORT_SYMBOL(input_get_poll_interval); + +/* SYSFS interface */ + +static ssize_t input_dev_get_poll_interval(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct input_dev *input = to_input_dev(dev); + + return sprintf(buf, "%d\n", input->poller->poll_interval); +} + +static ssize_t input_dev_set_poll_interval(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct input_dev *input = to_input_dev(dev); + struct input_dev_poller *poller = input->poller; + unsigned int interval; + int err; + + err = kstrtouint(buf, 0, &interval); + if (err) + return err; + + if (interval < poller->poll_interval_min) + return -EINVAL; + + if (interval > poller->poll_interval_max) + return -EINVAL; + + guard(mutex)(&input->mutex); + + poller->poll_interval = interval; + + if (input_device_enabled(input)) { + cancel_delayed_work_sync(&poller->work); + if (poller->poll_interval > 0) + input_dev_poller_queue_work(poller); + } + + return count; +} + +static DEVICE_ATTR(poll, 0644, + input_dev_get_poll_interval, input_dev_set_poll_interval); + +static ssize_t input_dev_get_poll_max(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct input_dev *input = to_input_dev(dev); + + return sprintf(buf, "%d\n", input->poller->poll_interval_max); +} + +static DEVICE_ATTR(max, 0444, input_dev_get_poll_max, NULL); + +static ssize_t input_dev_get_poll_min(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct input_dev *input = to_input_dev(dev); + + return sprintf(buf, "%d\n", input->poller->poll_interval_min); +} + +static DEVICE_ATTR(min, 0444, input_dev_get_poll_min, NULL); + +static umode_t input_poller_attrs_visible(struct kobject *kobj, + struct attribute *attr, int n) +{ + struct device *dev = kobj_to_dev(kobj); + struct input_dev *input = to_input_dev(dev); + + return input->poller ? attr->mode : 0; +} + +static struct attribute *input_poller_attrs[] = { + &dev_attr_poll.attr, + &dev_attr_max.attr, + &dev_attr_min.attr, + NULL +}; + +struct attribute_group input_poller_attribute_group = { + .is_visible = input_poller_attrs_visible, + .attrs = input_poller_attrs, +}; -- cgit v1.3.1