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/usb/misc/usb4604.c | 163 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 163 insertions(+) create mode 100644 drivers/usb/misc/usb4604.c (limited to 'drivers/usb/misc/usb4604.c') diff --git a/drivers/usb/misc/usb4604.c b/drivers/usb/misc/usb4604.c new file mode 100644 index 000000000..2ae965671 --- /dev/null +++ b/drivers/usb/misc/usb4604.c @@ -0,0 +1,163 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Driver for SMSC USB4604 USB HSIC 4-port 2.0 hub controller driver + * Based on usb3503 driver + * + * Copyright (c) 2012-2013 Dongjin Kim (tobetter@gmail.com) + * Copyright (c) 2016 Linaro Ltd. + */ + +#include +#include +#include +#include +#include + +enum usb4604_mode { + USB4604_MODE_UNKNOWN, + USB4604_MODE_HUB, + USB4604_MODE_STANDBY, +}; + +struct usb4604 { + enum usb4604_mode mode; + struct device *dev; + struct gpio_desc *gpio_reset; +}; + +static void usb4604_reset(struct usb4604 *hub, int state) +{ + gpiod_set_value_cansleep(hub->gpio_reset, state); + + /* Wait for i2c logic to come up */ + if (state) + msleep(250); +} + +static int usb4604_connect(struct usb4604 *hub) +{ + struct device *dev = hub->dev; + struct i2c_client *client = to_i2c_client(dev); + int err; + u8 connect_cmd[] = { 0xaa, 0x55, 0x00 }; + + usb4604_reset(hub, 1); + + err = i2c_master_send(client, connect_cmd, ARRAY_SIZE(connect_cmd)); + if (err < 0) { + usb4604_reset(hub, 0); + return err; + } + + hub->mode = USB4604_MODE_HUB; + dev_dbg(dev, "switched to HUB mode\n"); + + return 0; +} + +static int usb4604_switch_mode(struct usb4604 *hub, enum usb4604_mode mode) +{ + struct device *dev = hub->dev; + int err = 0; + + switch (mode) { + case USB4604_MODE_HUB: + err = usb4604_connect(hub); + break; + + case USB4604_MODE_STANDBY: + usb4604_reset(hub, 0); + dev_dbg(dev, "switched to STANDBY mode\n"); + break; + + default: + dev_err(dev, "unknown mode is requested\n"); + err = -EINVAL; + break; + } + + return err; +} + +static int usb4604_probe(struct usb4604 *hub) +{ + struct device *dev = hub->dev; + struct device_node *np = dev->of_node; + struct gpio_desc *gpio; + u32 mode = USB4604_MODE_HUB; + + gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW); + if (IS_ERR(gpio)) + return PTR_ERR(gpio); + hub->gpio_reset = gpio; + + if (of_property_read_u32(np, "initial-mode", &hub->mode)) + hub->mode = mode; + + return usb4604_switch_mode(hub, hub->mode); +} + +static int usb4604_i2c_probe(struct i2c_client *i2c) +{ + struct usb4604 *hub; + + hub = devm_kzalloc(&i2c->dev, sizeof(*hub), GFP_KERNEL); + if (!hub) + return -ENOMEM; + + i2c_set_clientdata(i2c, hub); + hub->dev = &i2c->dev; + + return usb4604_probe(hub); +} + +static int __maybe_unused usb4604_i2c_suspend(struct device *dev) +{ + struct i2c_client *client = to_i2c_client(dev); + struct usb4604 *hub = i2c_get_clientdata(client); + + usb4604_switch_mode(hub, USB4604_MODE_STANDBY); + + return 0; +} + +static int __maybe_unused usb4604_i2c_resume(struct device *dev) +{ + struct i2c_client *client = to_i2c_client(dev); + struct usb4604 *hub = i2c_get_clientdata(client); + + usb4604_switch_mode(hub, hub->mode); + + return 0; +} + +static SIMPLE_DEV_PM_OPS(usb4604_i2c_pm_ops, usb4604_i2c_suspend, + usb4604_i2c_resume); + +static const struct i2c_device_id usb4604_id[] = { + { .name = "usb4604" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, usb4604_id); + +#ifdef CONFIG_OF +static const struct of_device_id usb4604_of_match[] = { + { .compatible = "smsc,usb4604" }, + {} +}; +MODULE_DEVICE_TABLE(of, usb4604_of_match); +#endif + +static struct i2c_driver usb4604_i2c_driver = { + .driver = { + .name = "usb4604", + .pm = pm_ptr(&usb4604_i2c_pm_ops), + .of_match_table = of_match_ptr(usb4604_of_match), + }, + .probe = usb4604_i2c_probe, + .id_table = usb4604_id, +}; +module_i2c_driver(usb4604_i2c_driver); + +MODULE_DESCRIPTION("USB4604 USB HUB driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1