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, 252 insertions, 0 deletions

diff --git a/crypto/akcipher.c b/crypto/akcipher.c
new file mode 100644
index 000000000..630bb1973
--- /dev/null
+++ b/crypto/akcipher.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Public Key Encryption
+ *
+ * Copyright (c) 2015, Intel Corporation
+ * Authors: Tadeusz Struk <tadeusz.struk@intel.com>
+ */
+#include <crypto/internal/akcipher.h>
+#include <linux/cryptouser.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <net/netlink.h>
+
+#include "internal.h"
+
+#define CRYPTO_ALG_TYPE_AHASH_MASK	0x0000000e
+
+struct crypto_akcipher_sync_data {
+	struct crypto_akcipher *tfm;
+	const void *src;
+	void *dst;
+	unsigned int slen;
+	unsigned int dlen;
+
+	struct akcipher_request *req;
+	struct crypto_wait cwait;
+	struct scatterlist sg;
+	u8 *buf;
+};
+
+static int __maybe_unused crypto_akcipher_report(
+	struct sk_buff *skb, struct crypto_alg *alg)
+{
+	struct crypto_report_akcipher rakcipher = {
+		.type = "akcipher",
+	};
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_AKCIPHER,
+		       sizeof(rakcipher), &rakcipher);
+}
+
+static void __maybe_unused crypto_akcipher_show(struct seq_file *m,
+						struct crypto_alg *alg)
+{
+	seq_puts(m, "type         : akcipher\n");
+}
+
+static void crypto_akcipher_exit_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_akcipher *akcipher = __crypto_akcipher_tfm(tfm);
+	struct akcipher_alg *alg = crypto_akcipher_alg(akcipher);
+
+	alg->exit(akcipher);
+}
+
+static int crypto_akcipher_init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_akcipher *akcipher = __crypto_akcipher_tfm(tfm);
+	struct akcipher_alg *alg = crypto_akcipher_alg(akcipher);
+
+	if (alg->exit)
+		akcipher->base.exit = crypto_akcipher_exit_tfm;
+
+	if (alg->init)
+		return alg->init(akcipher);
+
+	return 0;
+}
+
+static void crypto_akcipher_free_instance(struct crypto_instance *inst)
+{
+	struct akcipher_instance *akcipher = akcipher_instance(inst);
+
+	akcipher->free(akcipher);
+}
+
+static const struct crypto_type crypto_akcipher_type = {
+	.extsize = crypto_alg_extsize,
+	.init_tfm = crypto_akcipher_init_tfm,
+	.free = crypto_akcipher_free_instance,
+#ifdef CONFIG_PROC_FS
+	.show = crypto_akcipher_show,
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_USER)
+	.report = crypto_akcipher_report,
+#endif
+	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
+	.maskset = CRYPTO_ALG_TYPE_AHASH_MASK,
+	.type = CRYPTO_ALG_TYPE_AKCIPHER,
+	.tfmsize = offsetof(struct crypto_akcipher, base),
+	.algsize = offsetof(struct akcipher_alg, base),
+};
+
+int crypto_grab_akcipher(struct crypto_akcipher_spawn *spawn,
+			 struct crypto_instance *inst,
+			 const char *name, u32 type, u32 mask)
+{
+	spawn->base.frontend = &crypto_akcipher_type;
+	return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_grab_akcipher);
+
+struct crypto_akcipher *crypto_alloc_akcipher(const char *alg_name, u32 type,
+					      u32 mask)
+{
+	return crypto_alloc_tfm(alg_name, &crypto_akcipher_type, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_akcipher);
+
+static void akcipher_prepare_alg(struct akcipher_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+
+	base->cra_type = &crypto_akcipher_type;
+	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
+	base->cra_flags |= CRYPTO_ALG_TYPE_AKCIPHER;
+}
+
+static int akcipher_default_op(struct akcipher_request *req)
+{
+	return -ENOSYS;
+}
+
+static int akcipher_default_set_key(struct crypto_akcipher *tfm,
+				     const void *key, unsigned int keylen)
+{
+	return -ENOSYS;
+}
+
+int crypto_register_akcipher(struct akcipher_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+
+	if (!alg->encrypt)
+		alg->encrypt = akcipher_default_op;
+	if (!alg->decrypt)
+		alg->decrypt = akcipher_default_op;
+	if (!alg->set_priv_key)
+		alg->set_priv_key = akcipher_default_set_key;
+
+	akcipher_prepare_alg(alg);
+	return crypto_register_alg(base);
+}
+EXPORT_SYMBOL_GPL(crypto_register_akcipher);
+
+void crypto_unregister_akcipher(struct akcipher_alg *alg)
+{
+	crypto_unregister_alg(&alg->base);
+}
+EXPORT_SYMBOL_GPL(crypto_unregister_akcipher);
+
+int akcipher_register_instance(struct crypto_template *tmpl,
+			       struct akcipher_instance *inst)
+{
+	if (WARN_ON(!inst->free))
+		return -EINVAL;
+	akcipher_prepare_alg(&inst->alg);
+	return crypto_register_instance(tmpl, akcipher_crypto_instance(inst));
+}
+EXPORT_SYMBOL_GPL(akcipher_register_instance);
+
+static int crypto_akcipher_sync_prep(struct crypto_akcipher_sync_data *data)
+{
+	unsigned int reqsize = crypto_akcipher_reqsize(data->tfm);
+	struct akcipher_request *req;
+	struct scatterlist *sg;
+	unsigned int mlen;
+	unsigned int len;
+	u8 *buf;
+
+	mlen = max(data->slen, data->dlen);
+
+	len = sizeof(*req) + reqsize + mlen;
+	if (len < mlen)
+		return -EOVERFLOW;
+
+	req = kzalloc(len, GFP_KERNEL);
+	if (!req)
+		return -ENOMEM;
+
+	data->req = req;
+	akcipher_request_set_tfm(req, data->tfm);
+
+	buf = (u8 *)(req + 1) + reqsize;
+	data->buf = buf;
+	memcpy(buf, data->src, data->slen);
+
+	sg = &data->sg;
+	sg_init_one(sg, buf, mlen);
+	akcipher_request_set_crypt(req, sg, sg, data->slen, data->dlen);
+
+	crypto_init_wait(&data->cwait);
+	akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
+				      crypto_req_done, &data->cwait);
+
+	return 0;
+}
+
+static int crypto_akcipher_sync_post(struct crypto_akcipher_sync_data *data,
+				     int err)
+{
+	err = crypto_wait_req(err, &data->cwait);
+	memcpy(data->dst, data->buf, data->dlen);
+	data->dlen = data->req->dst_len;
+	kfree_sensitive(data->req);
+	return err;
+}
+
+int crypto_akcipher_sync_encrypt(struct crypto_akcipher *tfm,
+				 const void *src, unsigned int slen,
+				 void *dst, unsigned int dlen)
+{
+	struct crypto_akcipher_sync_data data = {
+		.tfm = tfm,
+		.src = src,
+		.dst = dst,
+		.slen = slen,
+		.dlen = dlen,
+	};
+
+	return crypto_akcipher_sync_prep(&data) ?:
+	       crypto_akcipher_sync_post(&data,
+					 crypto_akcipher_encrypt(data.req));
+}
+EXPORT_SYMBOL_GPL(crypto_akcipher_sync_encrypt);
+
+int crypto_akcipher_sync_decrypt(struct crypto_akcipher *tfm,
+				 const void *src, unsigned int slen,
+				 void *dst, unsigned int dlen)
+{
+	struct crypto_akcipher_sync_data data = {
+		.tfm = tfm,
+		.src = src,
+		.dst = dst,
+		.slen = slen,
+		.dlen = dlen,
+	};
+
+	return crypto_akcipher_sync_prep(&data) ?:
+	       crypto_akcipher_sync_post(&data,
+					 crypto_akcipher_decrypt(data.req)) ?:
+	       data.dlen;
+}
+EXPORT_SYMBOL_GPL(crypto_akcipher_sync_decrypt);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Generic public key cipher type");