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, 228 insertions, 0 deletions

diff --git a/crypto/ecb.c b/crypto/ecb.c
new file mode 100644
index 000000000..cd1b20456
--- /dev/null
+++ b/crypto/ecb.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * ECB: Electronic CodeBook mode
+ *
+ * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <crypto/internal/cipher.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+static int crypto_ecb_crypt(struct crypto_cipher *cipher, const u8 *src,
+			    u8 *dst, unsigned nbytes, bool final,
+			    void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
+{
+	const unsigned int bsize = crypto_cipher_blocksize(cipher);
+
+	while (nbytes >= bsize) {
+		fn(crypto_cipher_tfm(cipher), dst, src);
+
+		src += bsize;
+		dst += bsize;
+
+		nbytes -= bsize;
+	}
+
+	return nbytes && final ? -EINVAL : nbytes;
+}
+
+static int crypto_ecb_encrypt2(struct crypto_lskcipher *tfm, const u8 *src,
+			       u8 *dst, unsigned len, u8 *iv, u32 flags)
+{
+	struct crypto_cipher **ctx = crypto_lskcipher_ctx(tfm);
+	struct crypto_cipher *cipher = *ctx;
+
+	return crypto_ecb_crypt(cipher, src, dst, len,
+				flags & CRYPTO_LSKCIPHER_FLAG_FINAL,
+				crypto_cipher_alg(cipher)->cia_encrypt);
+}
+
+static int crypto_ecb_decrypt2(struct crypto_lskcipher *tfm, const u8 *src,
+			       u8 *dst, unsigned len, u8 *iv, u32 flags)
+{
+	struct crypto_cipher **ctx = crypto_lskcipher_ctx(tfm);
+	struct crypto_cipher *cipher = *ctx;
+
+	return crypto_ecb_crypt(cipher, src, dst, len,
+				flags & CRYPTO_LSKCIPHER_FLAG_FINAL,
+				crypto_cipher_alg(cipher)->cia_decrypt);
+}
+
+static int lskcipher_setkey_simple2(struct crypto_lskcipher *tfm,
+				    const u8 *key, unsigned int keylen)
+{
+	struct crypto_cipher **ctx = crypto_lskcipher_ctx(tfm);
+	struct crypto_cipher *cipher = *ctx;
+
+	crypto_cipher_clear_flags(cipher, CRYPTO_TFM_REQ_MASK);
+	crypto_cipher_set_flags(cipher, crypto_lskcipher_get_flags(tfm) &
+				CRYPTO_TFM_REQ_MASK);
+	return crypto_cipher_setkey(cipher, key, keylen);
+}
+
+static int lskcipher_init_tfm_simple2(struct crypto_lskcipher *tfm)
+{
+	struct lskcipher_instance *inst = lskcipher_alg_instance(tfm);
+	struct crypto_cipher **ctx = crypto_lskcipher_ctx(tfm);
+	struct crypto_cipher_spawn *spawn;
+	struct crypto_cipher *cipher;
+
+	spawn = lskcipher_instance_ctx(inst);
+	cipher = crypto_spawn_cipher(spawn);
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	*ctx = cipher;
+	return 0;
+}
+
+static void lskcipher_exit_tfm_simple2(struct crypto_lskcipher *tfm)
+{
+	struct crypto_cipher **ctx = crypto_lskcipher_ctx(tfm);
+
+	crypto_free_cipher(*ctx);
+}
+
+static void lskcipher_free_instance_simple2(struct lskcipher_instance *inst)
+{
+	crypto_drop_cipher(lskcipher_instance_ctx(inst));
+	kfree(inst);
+}
+
+static struct lskcipher_instance *lskcipher_alloc_instance_simple2(
+	struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct crypto_cipher_spawn *spawn;
+	struct lskcipher_instance *inst;
+	struct crypto_alg *cipher_alg;
+	u32 mask;
+	int err;
+
+	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_LSKCIPHER, &mask);
+	if (err)
+		return ERR_PTR(err);
+
+	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
+	if (!inst)
+		return ERR_PTR(-ENOMEM);
+	spawn = lskcipher_instance_ctx(inst);
+
+	err = crypto_grab_cipher(spawn, lskcipher_crypto_instance(inst),
+				 crypto_attr_alg_name(tb[1]), 0, mask);
+	if (err)
+		goto err_free_inst;
+	cipher_alg = crypto_spawn_cipher_alg(spawn);
+
+	err = crypto_inst_setname(lskcipher_crypto_instance(inst), tmpl->name,
+				  cipher_alg);
+	if (err)
+		goto err_free_inst;
+
+	inst->free = lskcipher_free_instance_simple2;
+
+	/* Default algorithm properties, can be overridden */
+	inst->alg.co.base.cra_blocksize = cipher_alg->cra_blocksize;
+	inst->alg.co.base.cra_alignmask = cipher_alg->cra_alignmask;
+	inst->alg.co.base.cra_priority = cipher_alg->cra_priority;
+	inst->alg.co.min_keysize = cipher_alg->cra_cipher.cia_min_keysize;
+	inst->alg.co.max_keysize = cipher_alg->cra_cipher.cia_max_keysize;
+	inst->alg.co.ivsize = cipher_alg->cra_blocksize;
+
+	/* Use struct crypto_cipher * by default, can be overridden */
+	inst->alg.co.base.cra_ctxsize = sizeof(struct crypto_cipher *);
+	inst->alg.setkey = lskcipher_setkey_simple2;
+	inst->alg.init = lskcipher_init_tfm_simple2;
+	inst->alg.exit = lskcipher_exit_tfm_simple2;
+
+	return inst;
+
+err_free_inst:
+	lskcipher_free_instance_simple2(inst);
+	return ERR_PTR(err);
+}
+
+static int crypto_ecb_create2(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct lskcipher_instance *inst;
+	int err;
+
+	inst = lskcipher_alloc_instance_simple2(tmpl, tb);
+	if (IS_ERR(inst))
+		return PTR_ERR(inst);
+
+	/* ECB mode doesn't take an IV */
+	inst->alg.co.ivsize = 0;
+
+	inst->alg.encrypt = crypto_ecb_encrypt2;
+	inst->alg.decrypt = crypto_ecb_decrypt2;
+
+	err = lskcipher_register_instance(tmpl, inst);
+	if (err)
+		inst->free(inst);
+
+	return err;
+}
+
+static int crypto_ecb_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct crypto_lskcipher_spawn *spawn;
+	struct lskcipher_alg *cipher_alg;
+	struct lskcipher_instance *inst;
+	int err;
+
+	inst = lskcipher_alloc_instance_simple(tmpl, tb);
+	if (IS_ERR(inst)) {
+		err = crypto_ecb_create2(tmpl, tb);
+		return err;
+	}
+
+	spawn = lskcipher_instance_ctx(inst);
+	cipher_alg = crypto_lskcipher_spawn_alg(spawn);
+
+	/* ECB mode doesn't take an IV */
+	inst->alg.co.ivsize = 0;
+	if (cipher_alg->co.ivsize)
+		return -EINVAL;
+
+	inst->alg.co.base.cra_ctxsize = cipher_alg->co.base.cra_ctxsize;
+	inst->alg.setkey = cipher_alg->setkey;
+	inst->alg.encrypt = cipher_alg->encrypt;
+	inst->alg.decrypt = cipher_alg->decrypt;
+	inst->alg.init = cipher_alg->init;
+	inst->alg.exit = cipher_alg->exit;
+
+	err = lskcipher_register_instance(tmpl, inst);
+	if (err)
+		inst->free(inst);
+
+	return err;
+}
+
+static struct crypto_template crypto_ecb_tmpl = {
+	.name = "ecb",
+	.create = crypto_ecb_create,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_ecb_module_init(void)
+{
+	return crypto_register_template(&crypto_ecb_tmpl);
+}
+
+static void __exit crypto_ecb_module_exit(void)
+{
+	crypto_unregister_template(&crypto_ecb_tmpl);
+}
+
+module_init(crypto_ecb_module_init);
+module_exit(crypto_ecb_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ECB block cipher mode of operation");
+MODULE_ALIAS_CRYPTO("ecb");
+MODULE_IMPORT_NS("CRYPTO_INTERNAL");