sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

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 <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 202 insertions, 0 deletions

diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
new file mode 100644
index 000000000..f63676c44
--- /dev/null
+++ b/net/mac80211/pm.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Portions
+ * Copyright (C) 2020-2021, 2023-2024 Intel Corporation
+ */
+#include <net/mac80211.h>
+#include <net/rtnetlink.h>
+
+#include "ieee80211_i.h"
+#include "mesh.h"
+#include "driver-ops.h"
+#include "led.h"
+
+static void ieee80211_sched_scan_cancel(struct ieee80211_local *local)
+{
+	if (ieee80211_request_sched_scan_stop(local))
+		return;
+	cfg80211_sched_scan_stopped_locked(local->hw.wiphy, 0);
+}
+
+int __ieee80211_suspend(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan,
+			bool reset)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+	struct ieee80211_sub_if_data *sdata;
+	struct sta_info *sta;
+
+	if (!local->open_count)
+		goto suspend;
+
+	local->suspending = true;
+	mb(); /* make suspending visible before any cancellation */
+
+	ieee80211_scan_cancel(local);
+
+	ieee80211_dfs_cac_cancel(local, NULL);
+
+	ieee80211_roc_purge(local, NULL);
+
+	ieee80211_del_virtual_monitor(local);
+
+	if (ieee80211_hw_check(hw, AMPDU_AGGREGATION) &&
+	    !(wowlan && wowlan->any)) {
+		lockdep_assert_wiphy(local->hw.wiphy);
+		list_for_each_entry(sta, &local->sta_list, list) {
+			set_sta_flag(sta, WLAN_STA_BLOCK_BA);
+			ieee80211_sta_tear_down_BA_sessions(
+					sta, AGG_STOP_LOCAL_REQUEST);
+		}
+	}
+
+	/* keep sched_scan only in case of 'any' trigger */
+	if (!(wowlan && wowlan->any))
+		ieee80211_sched_scan_cancel(local);
+
+	ieee80211_stop_queues_by_reason(hw,
+					IEEE80211_MAX_QUEUE_MAP,
+					IEEE80211_QUEUE_STOP_REASON_SUSPEND,
+					false);
+
+	/* flush out all packets */
+	synchronize_net();
+
+	ieee80211_flush_queues(local, NULL, true);
+
+	local->quiescing = true;
+	/* make quiescing visible to timers everywhere */
+	mb();
+
+	flush_workqueue(local->workqueue);
+
+	/* Don't try to run timers while suspended. */
+	timer_delete_sync(&local->sta_cleanup);
+
+	 /*
+	 * Note that this particular timer doesn't need to be
+	 * restarted at resume.
+	 */
+	wiphy_work_cancel(local->hw.wiphy, &local->dynamic_ps_enable_work);
+	timer_delete_sync(&local->dynamic_ps_timer);
+
+	local->wowlan = wowlan;
+	if (local->wowlan) {
+		int err;
+
+		/* Drivers don't expect to suspend while some operations like
+		 * authenticating or associating are in progress. It doesn't
+		 * make sense anyway to accept that, since the authentication
+		 * or association would never finish since the driver can't do
+		 * that on its own.
+		 * Thus, clean up in-progress auth/assoc first.
+		 */
+		list_for_each_entry(sdata, &local->interfaces, list) {
+			if (!ieee80211_sdata_running(sdata))
+				continue;
+			if (sdata->vif.type != NL80211_IFTYPE_STATION)
+				continue;
+			ieee80211_mgd_quiesce(sdata);
+			/* If suspended during TX in progress, and wowlan
+			 * is enabled (connection will be active) there
+			 * can be a race where the driver is put out
+			 * of power-save due to TX and during suspend
+			 * dynamic_ps_timer is cancelled and TX packet
+			 * is flushed, leaving the driver in ACTIVE even
+			 * after resuming until dynamic_ps_timer puts
+			 * driver back in DOZE.
+			 */
+			if (sdata->u.mgd.associated &&
+			    sdata->u.mgd.powersave &&
+			     !(local->hw.conf.flags & IEEE80211_CONF_PS)) {
+				local->hw.conf.flags |= IEEE80211_CONF_PS;
+				ieee80211_hw_config(local, -1,
+						    IEEE80211_CONF_CHANGE_PS);
+			}
+		}
+
+		err = drv_suspend(local, wowlan);
+		if (err < 0) {
+			local->quiescing = false;
+			local->wowlan = false;
+			if (ieee80211_hw_check(hw, AMPDU_AGGREGATION)) {
+				lockdep_assert_wiphy(local->hw.wiphy);
+				list_for_each_entry(sta,
+						    &local->sta_list, list) {
+					clear_sta_flag(sta, WLAN_STA_BLOCK_BA);
+				}
+			}
+			ieee80211_wake_queues_by_reason(hw,
+					IEEE80211_MAX_QUEUE_MAP,
+					IEEE80211_QUEUE_STOP_REASON_SUSPEND,
+					false);
+			return err;
+		} else if (err > 0) {
+			WARN_ON(err != 1);
+			/* cfg80211 will call back into mac80211 to disconnect
+			 * all interfaces, allow that to proceed properly
+			 */
+			ieee80211_wake_queues_by_reason(hw,
+					IEEE80211_MAX_QUEUE_MAP,
+					IEEE80211_QUEUE_STOP_REASON_SUSPEND,
+					false);
+			return err;
+		} else {
+			goto suspend;
+		}
+	}
+
+	/* remove all interfaces that were created in the driver */
+	list_for_each_entry(sdata, &local->interfaces, list) {
+		if (!ieee80211_sdata_running(sdata))
+			continue;
+		switch (sdata->vif.type) {
+		case NL80211_IFTYPE_AP_VLAN:
+		case NL80211_IFTYPE_MONITOR:
+			continue;
+		case NL80211_IFTYPE_STATION:
+			ieee80211_mgd_quiesce(sdata);
+			break;
+		default:
+			break;
+		}
+
+		wiphy_delayed_work_flush(local->hw.wiphy,
+					 &sdata->dec_tailroom_needed_wk);
+		drv_remove_interface(local, sdata);
+	}
+
+	/*
+	 * We disconnected on all interfaces before suspend, all channel
+	 * contexts should be released, but on 'reset' debugfs that's
+	 * not true so don't check there.
+	 */
+	WARN_ON(!reset && !list_empty(&local->chanctx_list));
+
+	/* stop hardware - this must stop RX */
+	ieee80211_stop_device(local, true);
+
+ suspend:
+	local->suspended = true;
+	/* need suspended to be visible before quiescing is false */
+	barrier();
+	local->quiescing = false;
+	local->suspending = false;
+
+	return 0;
+}
+
+/*
+ * __ieee80211_resume() is a static inline which just calls
+ * ieee80211_reconfig(), which is also needed for hardware
+ * hang/firmware failure/etc. recovery.
+ */
+
+void ieee80211_report_wowlan_wakeup(struct ieee80211_vif *vif,
+				    struct cfg80211_wowlan_wakeup *wakeup,
+				    gfp_t gfp)
+{
+	struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
+
+	cfg80211_report_wowlan_wakeup(&sdata->wdev, wakeup, gfp);
+}
+EXPORT_SYMBOL(ieee80211_report_wowlan_wakeup);