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/wireless/ocb.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 net/wireless/ocb.c (limited to 'net/wireless/ocb.c') diff --git a/net/wireless/ocb.c b/net/wireless/ocb.c new file mode 100644 index 000000000..7d2d67f13 --- /dev/null +++ b/net/wireless/ocb.c @@ -0,0 +1,65 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * OCB mode implementation + * + * Copyright: (c) 2014 Czech Technical University in Prague + * (c) 2014 Volkswagen Group Research + * Copyright (C) 2022-2023 Intel Corporation + * Author: Rostislav Lisovy + * Funded by: Volkswagen Group Research + */ + +#include +#include +#include "nl80211.h" +#include "core.h" +#include "rdev-ops.h" + +int cfg80211_join_ocb(struct cfg80211_registered_device *rdev, + struct net_device *dev, + struct ocb_setup *setup) +{ + struct wireless_dev *wdev = dev->ieee80211_ptr; + int err; + + lockdep_assert_wiphy(wdev->wiphy); + + if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_OCB) + return -EOPNOTSUPP; + + if (!rdev->ops->join_ocb) + return -EOPNOTSUPP; + + if (WARN_ON(!setup->chandef.chan)) + return -EINVAL; + + err = rdev_join_ocb(rdev, dev, setup); + if (!err) + wdev->u.ocb.chandef = setup->chandef; + + return err; +} + +int cfg80211_leave_ocb(struct cfg80211_registered_device *rdev, + struct net_device *dev) +{ + struct wireless_dev *wdev = dev->ieee80211_ptr; + int err; + + lockdep_assert_wiphy(wdev->wiphy); + + if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_OCB) + return -EOPNOTSUPP; + + if (!rdev->ops->leave_ocb) + return -EOPNOTSUPP; + + if (!wdev->u.ocb.chandef.chan) + return -ENOTCONN; + + err = rdev_leave_ocb(rdev, dev); + if (!err) + memset(&wdev->u.ocb.chandef, 0, sizeof(wdev->u.ocb.chandef)); + + return err; +} -- cgit v1.3.1