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, 56 insertions, 0 deletions

diff --git a/net/wireless/Makefile b/net/wireless/Makefile
new file mode 100644
index 000000000..a77fd5ba6
--- /dev/null
+++ b/net/wireless/Makefile
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_CFG80211) += cfg80211.o
+obj-y += tests/
+
+obj-$(CONFIG_WEXT_CORE) += wext-core.o
+obj-$(CONFIG_WEXT_PROC) += wext-proc.o
+obj-$(CONFIG_WEXT_PRIV) += wext-priv.o
+
+cfg80211-y += core.o sysfs.o radiotap.o util.o reg.o scan.o nl80211.o
+cfg80211-y += mlme.o ibss.o sme.o chan.o ethtool.o mesh.o ap.o trace.o ocb.o
+cfg80211-y += michael-mic.o pmsr.o
+cfg80211-$(CONFIG_OF) += of.o
+cfg80211-$(CONFIG_CFG80211_DEBUGFS) += debugfs.o
+cfg80211-$(CONFIG_CFG80211_WEXT) += wext-compat.o wext-sme.o
+
+CFLAGS_trace.o := -I$(src)
+
+cfg80211-$(CONFIG_CFG80211_USE_KERNEL_REGDB_KEYS) += shipped-certs.o
+ifneq ($(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR),)
+cfg80211-y += extra-certs.o
+endif
+
+$(obj)/shipped-certs.c: $(sort $(wildcard $(src)/certs/*.hex))
+	@$(kecho) "  GEN     $@"
+	$(Q)(echo '#include "reg.h"'; \
+	  echo 'const u8 shipped_regdb_certs[] = {'; \
+	  echo | cat - $^ ; \
+	  echo '};'; \
+	  echo 'unsigned int shipped_regdb_certs_len = sizeof(shipped_regdb_certs);'; \
+	 ) > $@
+
+$(obj)/extra-certs.c: $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR) \
+		      $(sort $(wildcard $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR)/*.x509))
+	@$(kecho) "  GEN     $@"
+	$(Q)(set -e; \
+	  allf=""; \
+	  for f in $^ ; do \
+	      test -f $$f || continue;\
+	      # similar to hexdump -v -e '1/1 "0x%.2x," "\n"' \
+	      thisf=$$(od -An -v -tx1 < $$f | \
+	                   sed -e 's/ /\n/g' | \
+	                   sed -e 's/^[0-9a-f]\+$$/\0/;t;d' | \
+	                   sed -e 's/^/0x/;s/$$/,/'); \
+	      # file should not be empty - maybe command substitution failed? \
+	      test ! -z "$$thisf";\
+	      allf=$$allf$$thisf;\
+	  done; \
+	  ( \
+	      echo '#include "reg.h"'; \
+	      echo 'const u8 extra_regdb_certs[] = {'; \
+	      echo "$$allf"; \
+	      echo '};'; \
+	      echo 'unsigned int extra_regdb_certs_len = sizeof(extra_regdb_certs);'; \
+	  ) > $@)
+
+clean-files += shipped-certs.c extra-certs.c