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/mac80211/eht.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) create mode 100644 net/mac80211/eht.c (limited to 'net/mac80211/eht.c') diff --git a/net/mac80211/eht.c b/net/mac80211/eht.c new file mode 100644 index 000000000..23fe82df6 --- /dev/null +++ b/net/mac80211/eht.c @@ -0,0 +1,102 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * EHT handling + * + * Copyright(c) 2021-2026 Intel Corporation + */ + +#include "driver-ops.h" +#include "ieee80211_i.h" + +void +ieee80211_eht_cap_ie_to_sta_eht_cap(struct ieee80211_sub_if_data *sdata, + struct ieee80211_supported_band *sband, + const u8 *he_cap_ie, u8 he_cap_len, + const struct ieee80211_eht_cap_elem *eht_cap_ie_elem, + u8 eht_cap_len, + struct link_sta_info *link_sta) +{ + struct ieee80211_sta_eht_cap *eht_cap = &link_sta->pub->eht_cap; + struct ieee80211_he_cap_elem *he_cap_ie_elem = (void *)he_cap_ie; + u8 eht_ppe_size = 0; + u8 mcs_nss_size; + u8 eht_total_size = sizeof(eht_cap->eht_cap_elem); + u8 *pos = (u8 *)eht_cap_ie_elem; + + memset(eht_cap, 0, sizeof(*eht_cap)); + + if (!eht_cap_ie_elem || + !ieee80211_get_eht_iftype_cap_vif(sband, &sdata->vif)) + return; + + mcs_nss_size = ieee80211_eht_mcs_nss_size(he_cap_ie_elem, + &eht_cap_ie_elem->fixed, + sdata->vif.type == + NL80211_IFTYPE_STATION); + + eht_total_size += mcs_nss_size; + + /* Calculate the PPE thresholds length only if the header is present */ + if (eht_cap_ie_elem->fixed.phy_cap_info[5] & + IEEE80211_EHT_PHY_CAP5_PPE_THRESHOLD_PRESENT) { + u16 eht_ppe_hdr; + + if (eht_cap_len < eht_total_size + sizeof(u16)) + return; + + eht_ppe_hdr = get_unaligned_le16(eht_cap_ie_elem->optional + mcs_nss_size); + eht_ppe_size = + ieee80211_eht_ppe_size(eht_ppe_hdr, + eht_cap_ie_elem->fixed.phy_cap_info); + eht_total_size += eht_ppe_size; + + /* we calculate as if NSS > 8 are valid, but don't handle that */ + if (eht_ppe_size > sizeof(eht_cap->eht_ppe_thres)) + return; + } + + if (eht_cap_len < eht_total_size) + return; + + /* Copy the static portion of the EHT capabilities */ + memcpy(&eht_cap->eht_cap_elem, pos, sizeof(eht_cap->eht_cap_elem)); + pos += sizeof(eht_cap->eht_cap_elem); + + /* Copy MCS/NSS which depends on the peer capabilities */ + memset(&eht_cap->eht_mcs_nss_supp, 0, + sizeof(eht_cap->eht_mcs_nss_supp)); + memcpy(&eht_cap->eht_mcs_nss_supp, pos, mcs_nss_size); + + if (eht_ppe_size) + memcpy(eht_cap->eht_ppe_thres, + &eht_cap_ie_elem->optional[mcs_nss_size], + eht_ppe_size); + + eht_cap->has_eht = true; + + /* + * The MPDU length bits are reserved on all but 2.4 GHz and get set via + * VHT (5 GHz) or HE (6 GHz) capabilities. + */ + if (sband->band != NL80211_BAND_2GHZ) + return; + + switch (u8_get_bits(eht_cap->eht_cap_elem.mac_cap_info[0], + IEEE80211_EHT_MAC_CAP0_MAX_MPDU_LEN_MASK)) { + case IEEE80211_EHT_MAC_CAP0_MAX_MPDU_LEN_11454: + link_sta->pub->agg.max_amsdu_len = + IEEE80211_MAX_MPDU_LEN_VHT_11454; + break; + case IEEE80211_EHT_MAC_CAP0_MAX_MPDU_LEN_7991: + link_sta->pub->agg.max_amsdu_len = + IEEE80211_MAX_MPDU_LEN_VHT_7991; + break; + case IEEE80211_EHT_MAC_CAP0_MAX_MPDU_LEN_3895: + default: + link_sta->pub->agg.max_amsdu_len = + IEEE80211_MAX_MPDU_LEN_VHT_3895; + break; + } + + ieee80211_sta_recalc_aggregates(&link_sta->sta->sta); +} -- cgit v1.3.1