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/hid/hid-generic.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 drivers/hid/hid-generic.c (limited to 'drivers/hid/hid-generic.c') diff --git a/drivers/hid/hid-generic.c b/drivers/hid/hid-generic.c new file mode 100644 index 000000000..c2de91674 --- /dev/null +++ b/drivers/hid/hid-generic.c @@ -0,0 +1,98 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * HID support for Linux + * + * Copyright (c) 1999 Andreas Gal + * Copyright (c) 2000-2005 Vojtech Pavlik + * Copyright (c) 2005 Michael Haboustak for Concept2, Inc + * Copyright (c) 2007-2008 Oliver Neukum + * Copyright (c) 2006-2012 Jiri Kosina + * Copyright (c) 2012 Henrik Rydberg + */ + +/* + */ + +#include +#include +#include +#include +#include + +#include + +static struct hid_driver hid_generic; + +static int __check_hid_generic(struct device_driver *drv, void *data) +{ + struct hid_driver *hdrv = to_hid_driver(drv); + struct hid_device *hdev = data; + + if (hdrv == &hid_generic) + return 0; + + return hid_match_device(hdev, hdrv) != NULL; +} + +static bool hid_generic_match(struct hid_device *hdev, + bool ignore_special_driver) +{ + if (ignore_special_driver) + return true; + + if (hdev->quirks & HID_QUIRK_IGNORE_SPECIAL_DRIVER) + return true; + + if (hdev->quirks & HID_QUIRK_HAVE_SPECIAL_DRIVER) + return false; + + /* + * If any other driver wants the device, leave the device to this other + * driver. + */ + if (bus_for_each_drv(&hid_bus_type, NULL, hdev, __check_hid_generic)) + return false; + + return true; +} + +static int hid_generic_probe(struct hid_device *hdev, + const struct hid_device_id *id) +{ + int ret; + + hdev->quirks |= HID_QUIRK_INPUT_PER_APP; + + ret = hid_parse(hdev); + if (ret) + return ret; + + return hid_hw_start(hdev, HID_CONNECT_DEFAULT); +} + +static int hid_generic_reset_resume(struct hid_device *hdev) +{ + if (hdev->claimed & HID_CLAIMED_INPUT) + hidinput_reset_resume(hdev); + + return 0; +} + +static const struct hid_device_id hid_table[] = { + { HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, HID_ANY_ID, HID_ANY_ID) }, + { } +}; +MODULE_DEVICE_TABLE(hid, hid_table); + +static struct hid_driver hid_generic = { + .name = "hid-generic", + .id_table = hid_table, + .match = hid_generic_match, + .probe = hid_generic_probe, + .reset_resume = hid_generic_reset_resume, +}; +module_hid_driver(hid_generic); + +MODULE_AUTHOR("Henrik Rydberg"); +MODULE_DESCRIPTION("HID generic driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1