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, 315 insertions, 0 deletions

diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
new file mode 100644
index 000000000..a965b6aab
--- /dev/null
+++ b/include/crypto/internal/skcipher.h
@@ -0,0 +1,315 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Symmetric key ciphers.
+ * 
+ * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#ifndef _CRYPTO_INTERNAL_SKCIPHER_H
+#define _CRYPTO_INTERNAL_SKCIPHER_H
+
+#include <crypto/algapi.h>
+#include <crypto/internal/cipher.h>
+#include <crypto/skcipher.h>
+#include <linux/types.h>
+
+/*
+ * Set this if your algorithm is sync but needs a reqsize larger
+ * than MAX_SYNC_SKCIPHER_REQSIZE.
+ *
+ * Reuse bit that is specific to hash algorithms.
+ */
+#define CRYPTO_ALG_SKCIPHER_REQSIZE_LARGE CRYPTO_ALG_OPTIONAL_KEY
+
+struct aead_request;
+struct rtattr;
+
+struct skcipher_instance {
+	void (*free)(struct skcipher_instance *inst);
+	union {
+		struct {
+			char head[offsetof(struct skcipher_alg, base)];
+			struct crypto_instance base;
+		} s;
+		struct skcipher_alg alg;
+	};
+};
+
+struct lskcipher_instance {
+	void (*free)(struct lskcipher_instance *inst);
+	union {
+		struct {
+			char head[offsetof(struct lskcipher_alg, co.base)];
+			struct crypto_instance base;
+		} s;
+		struct lskcipher_alg alg;
+	};
+};
+
+struct crypto_skcipher_spawn {
+	struct crypto_spawn base;
+};
+
+struct crypto_lskcipher_spawn {
+	struct crypto_spawn base;
+};
+
+struct skcipher_walk {
+	union {
+		/* Virtual address of the source. */
+		struct {
+			struct {
+				const void *const addr;
+			} virt;
+		} src;
+
+		/* Private field for the API, do not use. */
+		struct scatter_walk in;
+	};
+
+	union {
+		/* Virtual address of the destination. */
+		struct {
+			struct {
+				void *const addr;
+			} virt;
+		} dst;
+
+		/* Private field for the API, do not use. */
+		struct scatter_walk out;
+	};
+
+	unsigned int nbytes;
+	unsigned int total;
+
+	u8 *page;
+	u8 *buffer;
+	u8 *oiv;
+	void *iv;
+
+	unsigned int ivsize;
+
+	int flags;
+	unsigned int blocksize;
+	unsigned int stride;
+	unsigned int alignmask;
+};
+
+static inline struct crypto_instance *skcipher_crypto_instance(
+	struct skcipher_instance *inst)
+{
+	return &inst->s.base;
+}
+
+static inline struct crypto_instance *lskcipher_crypto_instance(
+	struct lskcipher_instance *inst)
+{
+	return &inst->s.base;
+}
+
+static inline struct skcipher_instance *skcipher_alg_instance(
+	struct crypto_skcipher *skcipher)
+{
+	return container_of(crypto_skcipher_alg(skcipher),
+			    struct skcipher_instance, alg);
+}
+
+static inline struct lskcipher_instance *lskcipher_alg_instance(
+	struct crypto_lskcipher *lskcipher)
+{
+	return container_of(crypto_lskcipher_alg(lskcipher),
+			    struct lskcipher_instance, alg);
+}
+
+static inline void *skcipher_instance_ctx(struct skcipher_instance *inst)
+{
+	return crypto_instance_ctx(skcipher_crypto_instance(inst));
+}
+
+static inline void *lskcipher_instance_ctx(struct lskcipher_instance *inst)
+{
+	return crypto_instance_ctx(lskcipher_crypto_instance(inst));
+}
+
+static inline void skcipher_request_complete(struct skcipher_request *req, int err)
+{
+	crypto_request_complete(&req->base, err);
+}
+
+int crypto_grab_skcipher(struct crypto_skcipher_spawn *spawn,
+			 struct crypto_instance *inst,
+			 const char *name, u32 type, u32 mask);
+
+int crypto_grab_lskcipher(struct crypto_lskcipher_spawn *spawn,
+			  struct crypto_instance *inst,
+			  const char *name, u32 type, u32 mask);
+
+static inline void crypto_drop_skcipher(struct crypto_skcipher_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+static inline void crypto_drop_lskcipher(struct crypto_lskcipher_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+static inline struct lskcipher_alg *crypto_lskcipher_spawn_alg(
+	struct crypto_lskcipher_spawn *spawn)
+{
+	return container_of(spawn->base.alg, struct lskcipher_alg, co.base);
+}
+
+static inline struct skcipher_alg_common *crypto_spawn_skcipher_alg_common(
+	struct crypto_skcipher_spawn *spawn)
+{
+	return container_of(spawn->base.alg, struct skcipher_alg_common, base);
+}
+
+static inline struct lskcipher_alg *crypto_spawn_lskcipher_alg(
+	struct crypto_lskcipher_spawn *spawn)
+{
+	return crypto_lskcipher_spawn_alg(spawn);
+}
+
+static inline struct crypto_skcipher *crypto_spawn_skcipher(
+	struct crypto_skcipher_spawn *spawn)
+{
+	return crypto_spawn_tfm2(&spawn->base);
+}
+
+static inline struct crypto_lskcipher *crypto_spawn_lskcipher(
+	struct crypto_lskcipher_spawn *spawn)
+{
+	return crypto_spawn_tfm2(&spawn->base);
+}
+
+static inline void crypto_skcipher_set_reqsize(
+	struct crypto_skcipher *skcipher, unsigned int reqsize)
+{
+	skcipher->reqsize = reqsize;
+}
+
+static inline void crypto_skcipher_set_reqsize_dma(
+	struct crypto_skcipher *skcipher, unsigned int reqsize)
+{
+	reqsize += crypto_dma_align() & ~(crypto_tfm_ctx_alignment() - 1);
+	skcipher->reqsize = reqsize;
+}
+
+int crypto_register_skcipher(struct skcipher_alg *alg);
+void crypto_unregister_skcipher(struct skcipher_alg *alg);
+int crypto_register_skciphers(struct skcipher_alg *algs, int count);
+void crypto_unregister_skciphers(struct skcipher_alg *algs, int count);
+int skcipher_register_instance(struct crypto_template *tmpl,
+			       struct skcipher_instance *inst);
+
+int crypto_register_lskcipher(struct lskcipher_alg *alg);
+void crypto_unregister_lskcipher(struct lskcipher_alg *alg);
+int crypto_register_lskciphers(struct lskcipher_alg *algs, int count);
+void crypto_unregister_lskciphers(struct lskcipher_alg *algs, int count);
+int lskcipher_register_instance(struct crypto_template *tmpl,
+				struct lskcipher_instance *inst);
+
+int skcipher_walk_done(struct skcipher_walk *walk, int res);
+int skcipher_walk_virt(struct skcipher_walk *__restrict walk,
+		       struct skcipher_request *__restrict req,
+		       bool atomic);
+int skcipher_walk_aead_encrypt(struct skcipher_walk *__restrict walk,
+			       struct aead_request *__restrict req,
+			       bool atomic);
+int skcipher_walk_aead_decrypt(struct skcipher_walk *__restrict walk,
+			       struct aead_request *__restrict req,
+			       bool atomic);
+
+static inline void skcipher_walk_abort(struct skcipher_walk *walk)
+{
+	skcipher_walk_done(walk, -ECANCELED);
+}
+
+static inline void *crypto_skcipher_ctx(struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *crypto_lskcipher_ctx(struct crypto_lskcipher *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *crypto_skcipher_ctx_dma(struct crypto_skcipher *tfm)
+{
+	return crypto_tfm_ctx_dma(&tfm->base);
+}
+
+static inline bool crypto_skcipher_tested(struct crypto_skcipher *tfm)
+{
+	struct crypto_tfm *tfm_base = crypto_skcipher_tfm(tfm);
+
+	return tfm_base->__crt_alg->cra_flags & CRYPTO_ALG_TESTED;
+}
+
+static inline void *skcipher_request_ctx(struct skcipher_request *req)
+{
+	return req->__ctx;
+}
+
+static inline void *skcipher_request_ctx_dma(struct skcipher_request *req)
+{
+	unsigned int align = crypto_dma_align();
+
+	if (align <= crypto_tfm_ctx_alignment())
+		align = 1;
+
+	return PTR_ALIGN(skcipher_request_ctx(req), align);
+}
+
+static inline u32 skcipher_request_flags(struct skcipher_request *req)
+{
+	return req->base.flags;
+}
+
+/* Helpers for simple block cipher modes of operation */
+struct skcipher_ctx_simple {
+	struct crypto_cipher *cipher;	/* underlying block cipher */
+};
+static inline struct crypto_cipher *
+skcipher_cipher_simple(struct crypto_skcipher *tfm)
+{
+	struct skcipher_ctx_simple *ctx = crypto_skcipher_ctx(tfm);
+
+	return ctx->cipher;
+}
+
+struct skcipher_instance *skcipher_alloc_instance_simple(
+	struct crypto_template *tmpl, struct rtattr **tb);
+
+static inline struct crypto_alg *skcipher_ialg_simple(
+	struct skcipher_instance *inst)
+{
+	struct crypto_cipher_spawn *spawn = skcipher_instance_ctx(inst);
+
+	return crypto_spawn_cipher_alg(spawn);
+}
+
+static inline struct crypto_lskcipher *lskcipher_cipher_simple(
+	struct crypto_lskcipher *tfm)
+{
+	struct crypto_lskcipher **ctx = crypto_lskcipher_ctx(tfm);
+
+	return *ctx;
+}
+
+struct lskcipher_instance *lskcipher_alloc_instance_simple(
+	struct crypto_template *tmpl, struct rtattr **tb);
+
+static inline struct lskcipher_alg *lskcipher_ialg_simple(
+	struct lskcipher_instance *inst)
+{
+	struct crypto_lskcipher_spawn *spawn = lskcipher_instance_ctx(inst);
+
+	return crypto_lskcipher_spawn_alg(spawn);
+}
+
+#endif	/* _CRYPTO_INTERNAL_SKCIPHER_H */
+