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/of.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 127 insertions(+) create mode 100644 net/wireless/of.c (limited to 'net/wireless/of.c') diff --git a/net/wireless/of.c b/net/wireless/of.c new file mode 100644 index 000000000..99acbea3b --- /dev/null +++ b/net/wireless/of.c @@ -0,0 +1,127 @@ +// SPDX-License-Identifier: ISC +/* + * Copyright (C) 2017 Rafał Miłecki + */ + +#include +#include +#include "core.h" + +static bool wiphy_freq_limits_valid_chan(struct wiphy *wiphy, + struct ieee80211_freq_range *freq_limits, + unsigned int n_freq_limits, + struct ieee80211_channel *chan) +{ + u32 bw = MHZ_TO_KHZ(20); + int i; + + for (i = 0; i < n_freq_limits; i++) { + struct ieee80211_freq_range *limit = &freq_limits[i]; + + if (cfg80211_does_bw_fit_range(limit, + MHZ_TO_KHZ(chan->center_freq), + bw)) + return true; + } + + return false; +} + +static void wiphy_freq_limits_apply(struct wiphy *wiphy, + struct ieee80211_freq_range *freq_limits, + unsigned int n_freq_limits) +{ + enum nl80211_band band; + int i; + + if (WARN_ON(!n_freq_limits)) + return; + + for (band = 0; band < NUM_NL80211_BANDS; band++) { + struct ieee80211_supported_band *sband = wiphy->bands[band]; + + if (!sband) + continue; + + for (i = 0; i < sband->n_channels; i++) { + struct ieee80211_channel *chan = &sband->channels[i]; + + if (chan->flags & IEEE80211_CHAN_DISABLED) + continue; + + if (!wiphy_freq_limits_valid_chan(wiphy, freq_limits, + n_freq_limits, + chan)) { + pr_debug("Disabling freq %d MHz as it's out of OF limits\n", + chan->center_freq); + chan->flags |= IEEE80211_CHAN_DISABLED; + } + } + } +} + +void wiphy_read_of_freq_limits(struct wiphy *wiphy) +{ + struct device *dev = wiphy_dev(wiphy); + struct device_node *np; + struct property *prop; + struct ieee80211_freq_range *freq_limits; + unsigned int n_freq_limits; + const __be32 *p; + int len, i; + int err = 0; + + if (!dev) + return; + np = dev_of_node(dev); + if (!np) + return; + + prop = of_find_property(np, "ieee80211-freq-limit", &len); + if (!prop) + return; + + if (!len || len % sizeof(u32) || len / sizeof(u32) % 2) { + dev_err(dev, "ieee80211-freq-limit wrong format"); + return; + } + n_freq_limits = len / sizeof(u32) / 2; + + freq_limits = kzalloc_objs(*freq_limits, n_freq_limits); + if (!freq_limits) { + err = -ENOMEM; + goto out_kfree; + } + + p = NULL; + for (i = 0; i < n_freq_limits; i++) { + struct ieee80211_freq_range *limit = &freq_limits[i]; + + p = of_prop_next_u32(prop, p, &limit->start_freq_khz); + if (!p) { + err = -EINVAL; + goto out_kfree; + } + + p = of_prop_next_u32(prop, p, &limit->end_freq_khz); + if (!p) { + err = -EINVAL; + goto out_kfree; + } + + if (!limit->start_freq_khz || + !limit->end_freq_khz || + limit->start_freq_khz >= limit->end_freq_khz) { + err = -EINVAL; + goto out_kfree; + } + } + + wiphy_freq_limits_apply(wiphy, freq_limits, n_freq_limits); + +out_kfree: + kfree(freq_limits); + if (err) + dev_err(dev, "Failed to get limits: %d\n", err); +} +EXPORT_SYMBOL(wiphy_read_of_freq_limits); -- cgit v1.3.1