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/drivers/crypto/qce/cipher.h b/drivers/crypto/qce/cipher.h
new file mode 100644
index 000000000..850f257d0
--- /dev/null
+++ b/drivers/crypto/qce/cipher.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2010-2014, The Linux Foundation. All rights reserved.
+ */
+
+#ifndef _CIPHER_H_
+#define _CIPHER_H_
+
+#include "common.h"
+#include "core.h"
+
+#define QCE_MAX_KEY_SIZE	64
+
+struct qce_cipher_ctx {
+	u8 enc_key[QCE_MAX_KEY_SIZE];
+	unsigned int enc_keylen;
+	struct crypto_skcipher *fallback;
+};
+
+/**
+ * struct qce_cipher_reqctx - holds private cipher objects per request
+ * @flags: operation flags
+ * @iv: pointer to the IV
+ * @ivsize: IV size
+ * @src_nents: source entries
+ * @dst_nents: destination entries
+ * @result_sg: scatterlist used for result buffer
+ * @dst_tbl: destination sg table
+ * @dst_sg: destination sg pointer table beginning
+ * @src_tbl: source sg table
+ * @src_sg: source sg pointer table beginning;
+ * @cryptlen: crypto length
+ */
+struct qce_cipher_reqctx {
+	unsigned long flags;
+	u8 *iv;
+	unsigned int ivsize;
+	int src_nents;
+	int dst_nents;
+	struct scatterlist result_sg;
+	struct sg_table dst_tbl;
+	struct scatterlist *dst_sg;
+	struct scatterlist *src_sg;
+	unsigned int cryptlen;
+	struct skcipher_request fallback_req;	// keep at the end
+};
+
+static inline struct qce_alg_template *to_cipher_tmpl(struct crypto_skcipher *tfm)
+{
+	struct skcipher_alg *alg = crypto_skcipher_alg(tfm);
+	return container_of(alg, struct qce_alg_template, alg.skcipher);
+}
+
+extern const struct qce_algo_ops skcipher_ops;
+
+#endif /* _CIPHER_H_ */