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, 133 insertions, 0 deletions

diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
new file mode 100644
index 000000000..a6c2897bc
--- /dev/null
+++ b/include/keys/system_keyring.h
@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* System keyring containing trusted public keys.
+ *
+ * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _KEYS_SYSTEM_KEYRING_H
+#define _KEYS_SYSTEM_KEYRING_H
+
+#include <linux/key.h>
+
+enum blacklist_hash_type {
+	/* TBSCertificate hash */
+	BLACKLIST_HASH_X509_TBS = 1,
+	/* Raw data hash */
+	BLACKLIST_HASH_BINARY = 2,
+};
+
+#ifdef CONFIG_SYSTEM_TRUSTED_KEYRING
+
+extern int restrict_link_by_builtin_trusted(struct key *keyring,
+					    const struct key_type *type,
+					    const union key_payload *payload,
+					    struct key *restriction_key);
+int restrict_link_by_digsig_builtin(struct key *dest_keyring,
+				    const struct key_type *type,
+				    const union key_payload *payload,
+				    struct key *restriction_key);
+extern __init int load_module_cert(struct key *keyring);
+
+#else
+#define restrict_link_by_builtin_trusted restrict_link_reject
+#define restrict_link_by_digsig_builtin restrict_link_reject
+
+static inline __init int load_module_cert(struct key *keyring)
+{
+	return 0;
+}
+
+#endif
+
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+extern int restrict_link_by_builtin_and_secondary_trusted(
+	struct key *keyring,
+	const struct key_type *type,
+	const union key_payload *payload,
+	struct key *restriction_key);
+int restrict_link_by_digsig_builtin_and_secondary(struct key *keyring,
+						  const struct key_type *type,
+						  const union key_payload *payload,
+						  struct key *restriction_key);
+void __init add_to_secondary_keyring(const char *source, const void *data, size_t len);
+#else
+#define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted
+#define restrict_link_by_digsig_builtin_and_secondary restrict_link_by_digsig_builtin
+static inline void __init add_to_secondary_keyring(const char *source, const void *data, size_t len)
+{
+}
+#endif
+
+#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
+extern int restrict_link_by_builtin_secondary_and_machine(
+	struct key *dest_keyring,
+	const struct key_type *type,
+	const union key_payload *payload,
+	struct key *restrict_key);
+extern void __init set_machine_trusted_keys(struct key *keyring);
+#else
+#define restrict_link_by_builtin_secondary_and_machine restrict_link_by_builtin_trusted
+static inline void __init set_machine_trusted_keys(struct key *keyring)
+{
+}
+#endif
+
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+extern int mark_hash_blacklisted(const u8 *hash, size_t hash_len,
+			       enum blacklist_hash_type hash_type);
+extern int is_hash_blacklisted(const u8 *hash, size_t hash_len,
+			       enum blacklist_hash_type hash_type);
+extern int is_binary_blacklisted(const u8 *hash, size_t hash_len);
+#else
+static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len,
+				      enum blacklist_hash_type hash_type)
+{
+	return 0;
+}
+
+static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len)
+{
+	return 0;
+}
+#endif
+
+struct pkcs7_message;
+#ifdef CONFIG_SYSTEM_REVOCATION_LIST
+extern int add_key_to_revocation_list(const char *data, size_t size);
+extern int is_key_on_revocation_list(struct pkcs7_message *pkcs7);
+#else
+static inline int add_key_to_revocation_list(const char *data, size_t size)
+{
+	return 0;
+}
+static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
+{
+	return -ENOKEY;
+}
+#endif
+
+#ifdef CONFIG_IMA_BLACKLIST_KEYRING
+extern struct key *ima_blacklist_keyring;
+
+static inline struct key *get_ima_blacklist_keyring(void)
+{
+	return ima_blacklist_keyring;
+}
+#else
+static inline struct key *get_ima_blacklist_keyring(void)
+{
+	return NULL;
+}
+#endif /* CONFIG_IMA_BLACKLIST_KEYRING */
+
+#if defined(CONFIG_INTEGRITY_PLATFORM_KEYRING) && \
+	defined(CONFIG_SYSTEM_TRUSTED_KEYRING)
+extern void __init set_platform_trusted_keys(struct key *keyring);
+#else
+static inline void set_platform_trusted_keys(struct key *keyring)
+{
+}
+#endif
+
+#endif /* _KEYS_SYSTEM_KEYRING_H */