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 --- net/bluetooth/hci_sysfs.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 net/bluetooth/hci_sysfs.c (limited to 'net/bluetooth/hci_sysfs.c') diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c new file mode 100644 index 000000000..c2065abf7 --- /dev/null +++ b/net/bluetooth/hci_sysfs.c @@ -0,0 +1,151 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Bluetooth HCI driver model support. */ + +#include + +#include +#include + +static const struct class bt_class = { + .name = "bluetooth", +}; + +static void bt_link_release(struct device *dev) +{ + struct hci_conn *conn = to_hci_conn(dev); + struct device *parent = dev->parent; + + kfree(conn); + put_device(parent); +} + +static const struct device_type bt_link = { + .name = "link", + .release = bt_link_release, +}; + +/* + * The rfcomm tty device will possibly retain even when conn + * is down, and sysfs doesn't support move zombie device, + * so we should move the device before conn device is destroyed. + */ +static int __match_tty(struct device *dev, const void *data) +{ + return !strncmp(dev_name(dev), "rfcomm", 6); +} + +void hci_conn_init_sysfs(struct hci_conn *conn) +{ + struct hci_dev *hdev = conn->hdev; + + bt_dev_dbg(hdev, "conn %p", conn); + + conn->dev.type = &bt_link; + conn->dev.class = &bt_class; + conn->dev.parent = get_device(&hdev->dev); + + device_initialize(&conn->dev); +} + +void hci_conn_add_sysfs(struct hci_conn *conn) +{ + struct hci_dev *hdev = conn->hdev; + + bt_dev_dbg(hdev, "conn %p", conn); + + if (device_is_registered(&conn->dev)) + return; + + dev_set_name(&conn->dev, "%s:%d", hdev->name, conn->handle); + + if (device_add(&conn->dev) < 0) + bt_dev_err(hdev, "failed to register connection device"); +} + +void hci_conn_del_sysfs(struct hci_conn *conn) +{ + struct hci_dev *hdev = conn->hdev; + + bt_dev_dbg(hdev, "conn %p", conn); + + if (!device_is_registered(&conn->dev)) { + /* If device_add() has *not* succeeded, use *only* put_device() + * to drop the reference count. + */ + put_device(&conn->dev); + return; + } + + /* If there are devices using the connection as parent reset it to NULL + * before unregistering the device. + */ + while (1) { + struct device *dev; + + dev = device_find_child(&conn->dev, NULL, __match_tty); + if (!dev) + break; + device_move(dev, NULL, DPM_ORDER_DEV_LAST); + put_device(dev); + } + + device_unregister(&conn->dev); +} + +static void bt_host_release(struct device *dev) +{ + struct hci_dev *hdev = to_hci_dev(dev); + + if (hci_dev_test_flag(hdev, HCI_UNREGISTER)) { + hci_release_dev(hdev); + } else { + cleanup_srcu_struct(&hdev->srcu); + kfree(hdev); + } + module_put(THIS_MODULE); +} + +static ssize_t reset_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct hci_dev *hdev = to_hci_dev(dev); + + if (hdev->reset) + hdev->reset(hdev); + + return count; +} +static DEVICE_ATTR_WO(reset); + +static struct attribute *bt_host_attrs[] = { + &dev_attr_reset.attr, + NULL, +}; +ATTRIBUTE_GROUPS(bt_host); + +static const struct device_type bt_host = { + .name = "host", + .release = bt_host_release, + .groups = bt_host_groups, +}; + +void hci_init_sysfs(struct hci_dev *hdev) +{ + struct device *dev = &hdev->dev; + + dev->type = &bt_host; + dev->class = &bt_class; + + __module_get(THIS_MODULE); + device_initialize(dev); +} + +int __init bt_sysfs_init(void) +{ + return class_register(&bt_class); +} + +void bt_sysfs_cleanup(void) +{ + class_unregister(&bt_class); +} -- cgit v1.3.1