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, 89 insertions, 0 deletions

diff --git a/crypto/sm3.c b/crypto/sm3.c
new file mode 100644
index 000000000..05111a99b
--- /dev/null
+++ b/crypto/sm3.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * SM3 secure hash, as specified by OSCCA GM/T 0004-2012 SM3 and
+ * described at https://tools.ietf.org/html/draft-shen-sm3-hash-01
+ *
+ * Copyright (C) 2017 ARM Limited or its affiliates.
+ * Written by Gilad Ben-Yossef <gilad@benyossef.com>
+ * Copyright (C) 2021 Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
+ * Copyright 2026 Google LLC
+ */
+
+#include <crypto/internal/hash.h>
+#include <crypto/sm3.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define SM3_CTX(desc) ((struct sm3_ctx *)shash_desc_ctx(desc))
+
+static int crypto_sm3_init(struct shash_desc *desc)
+{
+	sm3_init(SM3_CTX(desc));
+	return 0;
+}
+
+static int crypto_sm3_update(struct shash_desc *desc,
+			     const u8 *data, unsigned int len)
+{
+	sm3_update(SM3_CTX(desc), data, len);
+	return 0;
+}
+
+static int crypto_sm3_final(struct shash_desc *desc, u8 *out)
+{
+	sm3_final(SM3_CTX(desc), out);
+	return 0;
+}
+
+static int crypto_sm3_digest(struct shash_desc *desc,
+			     const u8 *data, unsigned int len, u8 *out)
+{
+	sm3(data, len, out);
+	return 0;
+}
+
+static int crypto_sm3_export_core(struct shash_desc *desc, void *out)
+{
+	memcpy(out, SM3_CTX(desc), sizeof(struct sm3_ctx));
+	return 0;
+}
+
+static int crypto_sm3_import_core(struct shash_desc *desc, const void *in)
+{
+	memcpy(SM3_CTX(desc), in, sizeof(struct sm3_ctx));
+	return 0;
+}
+
+static struct shash_alg sm3_alg = {
+	.base.cra_name		= "sm3",
+	.base.cra_driver_name	= "sm3-lib",
+	.base.cra_priority	= 300,
+	.base.cra_blocksize	= SM3_BLOCK_SIZE,
+	.base.cra_module	= THIS_MODULE,
+	.digestsize		= SM3_DIGEST_SIZE,
+	.init			= crypto_sm3_init,
+	.update			= crypto_sm3_update,
+	.final			= crypto_sm3_final,
+	.digest			= crypto_sm3_digest,
+	.export_core		= crypto_sm3_export_core,
+	.import_core		= crypto_sm3_import_core,
+	.descsize		= sizeof(struct sm3_ctx),
+};
+
+static int __init crypto_sm3_mod_init(void)
+{
+	return crypto_register_shash(&sm3_alg);
+}
+module_init(crypto_sm3_mod_init);
+
+static void __exit crypto_sm3_mod_exit(void)
+{
+	crypto_unregister_shash(&sm3_alg);
+}
+module_exit(crypto_sm3_mod_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Crypto API support for SM3");
+
+MODULE_ALIAS_CRYPTO("sm3");
+MODULE_ALIAS_CRYPTO("sm3-lib");