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, 288 insertions, 0 deletions

diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h
new file mode 100644
index 000000000..05deea9da
--- /dev/null
+++ b/include/crypto/algapi.h
@@ -0,0 +1,288 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Cryptographic API for algorithms (i.e., low-level API).
+ *
+ * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+#ifndef _CRYPTO_ALGAPI_H
+#define _CRYPTO_ALGAPI_H
+
+#include <crypto/utils.h>
+#include <linux/align.h>
+#include <linux/cache.h>
+#include <linux/crypto.h>
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+/*
+ * Maximum values for blocksize and alignmask, used to allocate
+ * static buffers that are big enough for any combination of
+ * algs and architectures. Ciphers have a lower maximum size.
+ */
+#define MAX_ALGAPI_BLOCKSIZE		160
+#define MAX_ALGAPI_ALIGNMASK		127
+#define MAX_CIPHER_BLOCKSIZE		16
+#define MAX_CIPHER_ALIGNMASK		15
+
+#ifdef ARCH_DMA_MINALIGN
+#define CRYPTO_DMA_ALIGN ARCH_DMA_MINALIGN
+#else
+#define CRYPTO_DMA_ALIGN CRYPTO_MINALIGN
+#endif
+
+#define CRYPTO_DMA_PADDING ((CRYPTO_DMA_ALIGN - 1) & ~(CRYPTO_MINALIGN - 1))
+
+/*
+ * Autoloaded crypto modules should only use a prefixed name to avoid allowing
+ * arbitrary modules to be loaded. Loading from userspace may still need the
+ * unprefixed names, so retains those aliases as well.
+ * This uses __MODULE_INFO directly instead of MODULE_ALIAS because pre-4.3
+ * gcc (e.g. avr32 toolchain) uses __LINE__ for uniqueness, and this macro
+ * expands twice on the same line. Instead, use a separate base name for the
+ * alias.
+ */
+#define MODULE_ALIAS_CRYPTO(name)	\
+		MODULE_INFO(alias, name);	\
+		MODULE_INFO(alias, "crypto-" name)
+
+struct crypto_aead;
+struct crypto_instance;
+struct module;
+struct notifier_block;
+struct rtattr;
+struct scatterlist;
+struct seq_file;
+struct sk_buff;
+union crypto_no_such_thing;
+
+struct crypto_instance {
+	struct crypto_alg alg;
+
+	struct crypto_template *tmpl;
+
+	union {
+		/* Node in list of instances after registration. */
+		struct hlist_node list;
+		/* List of attached spawns before registration. */
+		struct crypto_spawn *spawns;
+	};
+
+	void *__ctx[] CRYPTO_MINALIGN_ATTR;
+};
+
+struct crypto_template {
+	struct list_head list;
+	struct hlist_head instances;
+	struct hlist_head dead;
+	struct module *module;
+
+	struct work_struct free_work;
+
+	int (*create)(struct crypto_template *tmpl, struct rtattr **tb);
+
+	char name[CRYPTO_MAX_ALG_NAME];
+};
+
+struct crypto_spawn {
+	struct list_head list;
+	struct crypto_alg *alg;
+	union {
+		/* Back pointer to instance after registration.*/
+		struct crypto_instance *inst;
+		/* Spawn list pointer prior to registration. */
+		struct crypto_spawn *next;
+	};
+	const struct crypto_type *frontend;
+	u32 mask;
+	bool dead;
+	bool registered;
+};
+
+struct crypto_queue {
+	struct list_head list;
+	struct list_head *backlog;
+
+	unsigned int qlen;
+	unsigned int max_qlen;
+};
+
+struct scatter_walk {
+	/* Must be the first member, see struct skcipher_walk. */
+	union {
+		void *const addr;
+
+		/* Private API field, do not touch. */
+		union crypto_no_such_thing *__addr;
+	};
+	struct scatterlist *sg;
+	unsigned int offset;
+};
+
+struct crypto_attr_alg {
+	char name[CRYPTO_MAX_ALG_NAME];
+};
+
+struct crypto_attr_type {
+	u32 type;
+	u32 mask;
+};
+
+/*
+ * Algorithm registration interface.
+ */
+int crypto_register_alg(struct crypto_alg *alg);
+void crypto_unregister_alg(struct crypto_alg *alg);
+int crypto_register_algs(struct crypto_alg *algs, int count);
+void crypto_unregister_algs(struct crypto_alg *algs, int count);
+
+void crypto_mod_put(struct crypto_alg *alg);
+
+int crypto_register_template(struct crypto_template *tmpl);
+int crypto_register_templates(struct crypto_template *tmpls, int count);
+void crypto_unregister_template(struct crypto_template *tmpl);
+void crypto_unregister_templates(struct crypto_template *tmpls, int count);
+struct crypto_template *crypto_lookup_template(const char *name);
+
+int crypto_register_instance(struct crypto_template *tmpl,
+			     struct crypto_instance *inst);
+void crypto_unregister_instance(struct crypto_instance *inst);
+
+int crypto_grab_spawn(struct crypto_spawn *spawn, struct crypto_instance *inst,
+		      const char *name, u32 type, u32 mask);
+void crypto_drop_spawn(struct crypto_spawn *spawn);
+struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type,
+				    u32 mask);
+void *crypto_spawn_tfm2(struct crypto_spawn *spawn);
+
+struct crypto_attr_type *crypto_get_attr_type(struct rtattr **tb);
+int crypto_check_attr_type(struct rtattr **tb, u32 type, u32 *mask_ret);
+const char *crypto_attr_alg_name(struct rtattr *rta);
+int __crypto_inst_setname(struct crypto_instance *inst, const char *name,
+			  const char *driver, struct crypto_alg *alg);
+
+#define crypto_inst_setname(inst, name, ...) \
+	CONCATENATE(crypto_inst_setname_, COUNT_ARGS(__VA_ARGS__))( \
+		inst, name, ##__VA_ARGS__)
+#define crypto_inst_setname_1(inst, name, alg) \
+	__crypto_inst_setname(inst, name, name, alg)
+#define crypto_inst_setname_2(inst, name, driver, alg) \
+	__crypto_inst_setname(inst, name, driver, alg)
+
+void crypto_init_queue(struct crypto_queue *queue, unsigned int max_qlen);
+int crypto_enqueue_request(struct crypto_queue *queue,
+			   struct crypto_async_request *request);
+void crypto_enqueue_request_head(struct crypto_queue *queue,
+				 struct crypto_async_request *request);
+struct crypto_async_request *crypto_dequeue_request(struct crypto_queue *queue);
+static inline unsigned int crypto_queue_len(struct crypto_queue *queue)
+{
+	return queue->qlen;
+}
+
+void crypto_inc(u8 *a, unsigned int size);
+
+static inline void *crypto_tfm_ctx(struct crypto_tfm *tfm)
+{
+	return tfm->__crt_ctx;
+}
+
+static inline void *crypto_tfm_ctx_align(struct crypto_tfm *tfm,
+					 unsigned int align)
+{
+	if (align <= crypto_tfm_ctx_alignment())
+		align = 1;
+
+	return PTR_ALIGN(crypto_tfm_ctx(tfm), align);
+}
+
+static inline unsigned int crypto_dma_align(void)
+{
+	return CRYPTO_DMA_ALIGN;
+}
+
+static inline unsigned int crypto_dma_padding(void)
+{
+	return (crypto_dma_align() - 1) & ~(crypto_tfm_ctx_alignment() - 1);
+}
+
+static inline void *crypto_tfm_ctx_dma(struct crypto_tfm *tfm)
+{
+	return crypto_tfm_ctx_align(tfm, crypto_dma_align());
+}
+
+static inline struct crypto_instance *crypto_tfm_alg_instance(
+	struct crypto_tfm *tfm)
+{
+	return container_of(tfm->__crt_alg, struct crypto_instance, alg);
+}
+
+static inline void *crypto_instance_ctx(struct crypto_instance *inst)
+{
+	return inst->__ctx;
+}
+
+static inline struct crypto_async_request *crypto_get_backlog(
+	struct crypto_queue *queue)
+{
+	return queue->backlog == &queue->list ? NULL :
+	       container_of(queue->backlog, struct crypto_async_request, list);
+}
+
+static inline u32 crypto_requires_off(struct crypto_attr_type *algt, u32 off)
+{
+	return (algt->type ^ off) & algt->mask & off;
+}
+
+/*
+ * When an algorithm uses another algorithm (e.g., if it's an instance of a
+ * template), these are the flags that should always be set on the "outer"
+ * algorithm if any "inner" algorithm has them set.
+ */
+#define CRYPTO_ALG_INHERITED_FLAGS	\
+	(CRYPTO_ALG_ASYNC | CRYPTO_ALG_NEED_FALLBACK |	\
+	 CRYPTO_ALG_ALLOCATES_MEMORY)
+
+/*
+ * Given the type and mask that specify the flags restrictions on a template
+ * instance being created, return the mask that should be passed to
+ * crypto_grab_*() (along with type=0) to honor any request the user made to
+ * have any of the CRYPTO_ALG_INHERITED_FLAGS clear.
+ */
+static inline u32 crypto_algt_inherited_mask(struct crypto_attr_type *algt)
+{
+	return crypto_requires_off(algt, CRYPTO_ALG_INHERITED_FLAGS);
+}
+
+int crypto_register_notifier(struct notifier_block *nb);
+int crypto_unregister_notifier(struct notifier_block *nb);
+
+/* Crypto notification events. */
+enum {
+	CRYPTO_MSG_ALG_REQUEST,
+	CRYPTO_MSG_ALG_REGISTER,
+	CRYPTO_MSG_ALG_LOADED,
+};
+
+static inline void crypto_request_complete(struct crypto_async_request *req,
+					   int err)
+{
+	req->complete(req->data, err);
+}
+
+static inline u32 crypto_tfm_alg_type(struct crypto_tfm *tfm)
+{
+	return tfm->__crt_alg->cra_flags & CRYPTO_ALG_TYPE_MASK;
+}
+
+static inline bool crypto_tfm_req_virt(struct crypto_tfm *tfm)
+{
+	return tfm->__crt_alg->cra_flags & CRYPTO_ALG_REQ_VIRT;
+}
+
+static inline u32 crypto_request_flags(struct crypto_async_request *req)
+{
+	return req->flags & ~CRYPTO_TFM_REQ_ON_STACK;
+}
+
+#endif	/* _CRYPTO_ALGAPI_H */