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, 151 insertions, 0 deletions

diff --git a/net/nfc/nfc.h b/net/nfc/nfc.h
new file mode 100644
index 000000000..0b1e6466f
--- /dev/null
+++ b/net/nfc/nfc.h
@@ -0,0 +1,151 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2011 Instituto Nokia de Tecnologia
+ *
+ * Authors:
+ *    Lauro Ramos Venancio <lauro.venancio@openbossa.org>
+ *    Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
+ */
+
+#ifndef __LOCAL_NFC_H
+#define __LOCAL_NFC_H
+
+#include <net/nfc/nfc.h>
+#include <net/sock.h>
+
+#define NFC_TARGET_MODE_IDLE 0
+#define NFC_TARGET_MODE_SLEEP 1
+
+struct nfc_protocol {
+	int id;
+	struct proto *proto;
+	struct module *owner;
+	int (*create)(struct net *net, struct socket *sock,
+		      const struct nfc_protocol *nfc_proto, int kern);
+};
+
+struct nfc_rawsock {
+	struct sock sk;
+	struct nfc_dev *dev;
+	u32 target_idx;
+	struct work_struct tx_work;
+	bool tx_work_scheduled;
+};
+
+struct nfc_sock_list {
+	struct hlist_head head;
+	rwlock_t          lock;
+};
+
+#define nfc_rawsock(sk) ((struct nfc_rawsock *) sk)
+#define to_rawsock_sk(_tx_work) \
+	((struct sock *) container_of(_tx_work, struct nfc_rawsock, tx_work))
+
+struct nfc_llcp_sdp_tlv;
+
+void nfc_llcp_mac_is_down(struct nfc_dev *dev);
+void nfc_llcp_mac_is_up(struct nfc_dev *dev, u32 target_idx,
+			u8 comm_mode, u8 rf_mode);
+int nfc_llcp_register_device(struct nfc_dev *dev);
+void nfc_llcp_unregister_device(struct nfc_dev *dev);
+int nfc_llcp_set_remote_gb(struct nfc_dev *dev, const u8 *gb, u8 gb_len);
+u8 *nfc_llcp_general_bytes(struct nfc_dev *dev, size_t *general_bytes_len);
+int nfc_llcp_data_received(struct nfc_dev *dev, struct sk_buff *skb);
+struct nfc_llcp_local *nfc_llcp_find_local(struct nfc_dev *dev);
+int nfc_llcp_local_put(struct nfc_llcp_local *local);
+int __init nfc_llcp_init(void);
+void nfc_llcp_exit(void);
+void nfc_llcp_free_sdp_tlv(struct nfc_llcp_sdp_tlv *sdp);
+void nfc_llcp_free_sdp_tlv_list(struct hlist_head *head);
+
+int __init rawsock_init(void);
+void rawsock_exit(void);
+
+int __init af_nfc_init(void);
+void af_nfc_exit(void);
+int nfc_proto_register(const struct nfc_protocol *nfc_proto);
+void nfc_proto_unregister(const struct nfc_protocol *nfc_proto);
+
+extern int nfc_devlist_generation;
+extern struct mutex nfc_devlist_mutex;
+
+int __init nfc_genl_init(void);
+void nfc_genl_exit(void);
+
+void nfc_genl_data_init(struct nfc_genl_data *genl_data);
+void nfc_genl_data_exit(struct nfc_genl_data *genl_data);
+
+int nfc_genl_targets_found(struct nfc_dev *dev);
+int nfc_genl_target_lost(struct nfc_dev *dev, u32 target_idx);
+
+int nfc_genl_device_added(struct nfc_dev *dev);
+int nfc_genl_device_removed(struct nfc_dev *dev);
+
+int nfc_genl_dep_link_up_event(struct nfc_dev *dev, u32 target_idx,
+			       u8 comm_mode, u8 rf_mode);
+int nfc_genl_dep_link_down_event(struct nfc_dev *dev);
+
+int nfc_genl_tm_activated(struct nfc_dev *dev, u32 protocol);
+int nfc_genl_tm_deactivated(struct nfc_dev *dev);
+
+int nfc_genl_llc_send_sdres(struct nfc_dev *dev, struct hlist_head *sdres_list);
+
+int nfc_genl_se_added(struct nfc_dev *dev, u32 se_idx, u16 type);
+int nfc_genl_se_removed(struct nfc_dev *dev, u32 se_idx);
+int nfc_genl_se_transaction(struct nfc_dev *dev, u8 se_idx,
+			    struct nfc_evt_transaction *evt_transaction);
+int nfc_genl_se_connectivity(struct nfc_dev *dev, u8 se_idx);
+
+struct nfc_dev *nfc_get_device(unsigned int idx);
+
+static inline void nfc_put_device(struct nfc_dev *dev)
+{
+	put_device(&dev->dev);
+}
+
+static inline void nfc_device_iter_init(struct class_dev_iter *iter)
+{
+	class_dev_iter_init(iter, &nfc_class, NULL, NULL);
+}
+
+static inline struct nfc_dev *nfc_device_iter_next(struct class_dev_iter *iter)
+{
+	struct device *d = class_dev_iter_next(iter);
+	if (!d)
+		return NULL;
+
+	return to_nfc_dev(d);
+}
+
+static inline void nfc_device_iter_exit(struct class_dev_iter *iter)
+{
+	class_dev_iter_exit(iter);
+}
+
+int nfc_fw_download(struct nfc_dev *dev, const char *firmware_name);
+int nfc_genl_fw_download_done(struct nfc_dev *dev, const char *firmware_name,
+			      u32 result);
+
+int nfc_dev_up(struct nfc_dev *dev);
+
+int nfc_dev_down(struct nfc_dev *dev);
+
+int nfc_start_poll(struct nfc_dev *dev, u32 im_protocols, u32 tm_protocols);
+
+int nfc_stop_poll(struct nfc_dev *dev);
+
+int nfc_dep_link_up(struct nfc_dev *dev, int target_idx, u8 comm_mode);
+
+int nfc_dep_link_down(struct nfc_dev *dev);
+
+int nfc_activate_target(struct nfc_dev *dev, u32 target_idx, u32 protocol);
+
+int nfc_deactivate_target(struct nfc_dev *dev, u32 target_idx, u8 mode);
+
+int nfc_data_exchange(struct nfc_dev *dev, u32 target_idx, struct sk_buff *skb,
+		      data_exchange_cb_t cb, void *cb_context);
+
+int nfc_enable_se(struct nfc_dev *dev, u32 se_idx);
+int nfc_disable_se(struct nfc_dev *dev, u32 se_idx);
+
+#endif /* __LOCAL_NFC_H */