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, 286 insertions, 0 deletions

diff --git a/net/mac80211/tests/mfp.c b/net/mac80211/tests/mfp.c
new file mode 100644
index 000000000..58e675e0e
--- /dev/null
+++ b/net/mac80211/tests/mfp.c
@@ -0,0 +1,286 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for management frame acceptance
+ *
+ * Copyright (C) 2023 Intel Corporation
+ */
+#include <kunit/test.h>
+#include <kunit/skbuff.h>
+#include "../ieee80211_i.h"
+#include "../sta_info.h"
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+
+static const struct mfp_test_case {
+	const char *desc;
+	bool sta, mfp, decrypted, unicast, assoc;
+	u8 category;
+	u8 stype;
+	u8 action;
+	ieee80211_rx_result result;
+} accept_mfp_cases[] = {
+	/* regular public action */
+	{
+		.desc = "public action: accept unicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: accept multicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: accept unicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: accept multicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "public action: drop unicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_UNICAST_PUB_ACTION,
+	},
+	{
+		.desc = "public action: accept multicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PUBLIC,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.mfp = true,
+		.result = RX_CONTINUE,
+	},
+	/* protected dual of public action */
+	{
+		.desc = "protected dual: drop unicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop multicast from unknown peer",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop unicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop multicast without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop undecrypted unicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: drop undecrypted multicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.unicast = false,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_DUAL,
+	},
+	{
+		.desc = "protected dual: accept unicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.decrypted = true,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "protected dual: accept multicast with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_PROTECTED_DUAL_OF_ACTION,
+		.action = WLAN_PUB_ACTION_DSE_ENABLEMENT,
+		.decrypted = true,
+		.unicast = false,
+		.sta = true,
+		.mfp = true,
+		.result = RX_CONTINUE,
+	},
+	/* deauth/disassoc before keys are set */
+	{
+		.desc = "deauth: accept unicast with MFP but w/o key",
+		.stype = IEEE80211_STYPE_DEAUTH,
+		.sta = true,
+		.mfp = true,
+		.unicast = true,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "disassoc: accept unicast with MFP but w/o key",
+		.stype = IEEE80211_STYPE_DEAUTH,
+		.sta = true,
+		.mfp = true,
+		.unicast = true,
+		.result = RX_CONTINUE,
+	},
+	/* non-public robust action frame ... */
+	{
+		.desc = "BA action: drop unicast before assoc",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.result = RX_DROP_U_UNPROT_ROBUST_ACTION,
+	},
+	{
+		.desc = "BA action: drop unprotected after assoc",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_UCAST_MGMT,
+	},
+	{
+		.desc = "BA action: accept unprotected without MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.assoc = true,
+		.mfp = false,
+		.result = RX_CONTINUE,
+	},
+	{
+		.desc = "BA action: drop unprotected with MFP",
+		.stype = IEEE80211_STYPE_ACTION,
+		.category = WLAN_CATEGORY_BACK,
+		.unicast = true,
+		.sta = true,
+		.mfp = true,
+		.result = RX_DROP_U_UNPROT_UCAST_MGMT,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(accept_mfp, accept_mfp_cases, desc);
+
+static void accept_mfp(struct kunit *test)
+{
+	static struct sta_info sta;
+	const struct mfp_test_case *params = test->param_value;
+	struct ieee80211_rx_data rx = {
+		.sta = params->sta ? &sta : NULL,
+	};
+	struct ieee80211_rx_status *status;
+	struct ieee80211_hdr_3addr hdr = {
+		.frame_control = cpu_to_le16(IEEE80211_FTYPE_MGMT |
+					     params->stype),
+		.addr1 = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
+		.addr2 = { 0x12, 0x22, 0x33, 0x44, 0x55, 0x66 },
+		/* A3/BSSID doesn't matter here */
+	};
+
+	memset(&sta, 0, sizeof(sta));
+
+	if (!params->sta) {
+		KUNIT_ASSERT_FALSE(test, params->mfp);
+		KUNIT_ASSERT_FALSE(test, params->decrypted);
+	}
+
+	if (params->mfp)
+		set_sta_flag(&sta, WLAN_STA_MFP);
+
+	if (params->assoc)
+		set_bit(WLAN_STA_ASSOC, &sta._flags);
+
+	rx.skb = kunit_zalloc_skb(test, 128, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, rx.skb);
+	status = IEEE80211_SKB_RXCB(rx.skb);
+
+	if (params->decrypted) {
+		status->flag |= RX_FLAG_DECRYPTED;
+		if (params->unicast)
+			hdr.frame_control |=
+				cpu_to_le16(IEEE80211_FCTL_PROTECTED);
+	}
+
+	if (params->unicast)
+		hdr.addr1[0] = 0x02;
+
+	skb_put_data(rx.skb, &hdr, sizeof(hdr));
+
+	switch (params->stype) {
+	case IEEE80211_STYPE_ACTION:
+		skb_put_u8(rx.skb, params->category);
+		skb_put_u8(rx.skb, params->action);
+		break;
+	case IEEE80211_STYPE_DEAUTH:
+	case IEEE80211_STYPE_DISASSOC: {
+		__le16 reason = cpu_to_le16(WLAN_REASON_UNSPECIFIED);
+
+		skb_put_data(rx.skb, &reason, sizeof(reason));
+		}
+		break;
+	}
+
+	KUNIT_EXPECT_EQ(test,
+			(__force u32)ieee80211_drop_unencrypted_mgmt(&rx),
+			(__force u32)params->result);
+}
+
+static struct kunit_case mfp_test_cases[] = {
+	KUNIT_CASE_PARAM(accept_mfp, accept_mfp_gen_params),
+	{}
+};
+
+static struct kunit_suite mfp = {
+	.name = "mac80211-mfp",
+	.test_cases = mfp_test_cases,
+};
+
+kunit_test_suite(mfp);