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, 240 insertions, 0 deletions

diff --git a/crypto/sha1.c b/crypto/sha1.c
new file mode 100644
index 000000000..4fbf61cf0
--- /dev/null
+++ b/crypto/sha1.c
@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Crypto API support for SHA-1 and HMAC-SHA1
+ *
+ * Copyright (c) Alan Smithee.
+ * Copyright (c) Andrew McDonald <andrew@mcdonald.org.uk>
+ * Copyright (c) Jean-Francois Dive <jef@linuxbe.org>
+ * Copyright 2025 Google LLC
+ */
+#include <crypto/internal/hash.h>
+#include <crypto/sha1.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+/*
+ * Export and import functions.  crypto_shash wants a particular format that
+ * matches that used by some legacy drivers.  It currently is the same as the
+ * library SHA context, except the value in bytecount must be block-aligned and
+ * the remainder must be stored in an extra u8 appended to the struct.
+ */
+
+#define SHA1_SHASH_STATE_SIZE (sizeof(struct sha1_ctx) + 1)
+static_assert(sizeof(struct sha1_ctx) == sizeof(struct sha1_state));
+static_assert(offsetof(struct sha1_ctx, state) == offsetof(struct sha1_state, state));
+static_assert(offsetof(struct sha1_ctx, bytecount) == offsetof(struct sha1_state, count));
+static_assert(offsetof(struct sha1_ctx, buf) == offsetof(struct sha1_state, buffer));
+
+static int __crypto_sha1_export(const struct sha1_ctx *ctx0, void *out)
+{
+	struct sha1_ctx ctx = *ctx0;
+	unsigned int partial;
+	u8 *p = out;
+
+	partial = ctx.bytecount % SHA1_BLOCK_SIZE;
+	ctx.bytecount -= partial;
+	memcpy(p, &ctx, sizeof(ctx));
+	p += sizeof(ctx);
+	*p = partial;
+	return 0;
+}
+
+static int __crypto_sha1_import(struct sha1_ctx *ctx, const void *in)
+{
+	const u8 *p = in;
+
+	memcpy(ctx, p, sizeof(*ctx));
+	p += sizeof(*ctx);
+	ctx->bytecount += *p;
+	return 0;
+}
+
+static int __crypto_sha1_export_core(const struct sha1_ctx *ctx, void *out)
+{
+	memcpy(out, ctx, offsetof(struct sha1_ctx, buf));
+	return 0;
+}
+
+static int __crypto_sha1_import_core(struct sha1_ctx *ctx, const void *in)
+{
+	memcpy(ctx, in, offsetof(struct sha1_ctx, buf));
+	return 0;
+}
+
+const u8 sha1_zero_message_hash[SHA1_DIGEST_SIZE] = {
+	0xda, 0x39, 0xa3, 0xee, 0x5e, 0x6b, 0x4b, 0x0d,
+	0x32, 0x55, 0xbf, 0xef, 0x95, 0x60, 0x18, 0x90,
+	0xaf, 0xd8, 0x07, 0x09
+};
+EXPORT_SYMBOL_GPL(sha1_zero_message_hash);
+
+#define SHA1_CTX(desc) ((struct sha1_ctx *)shash_desc_ctx(desc))
+
+static int crypto_sha1_init(struct shash_desc *desc)
+{
+	sha1_init(SHA1_CTX(desc));
+	return 0;
+}
+
+static int crypto_sha1_update(struct shash_desc *desc,
+			      const u8 *data, unsigned int len)
+{
+	sha1_update(SHA1_CTX(desc), data, len);
+	return 0;
+}
+
+static int crypto_sha1_final(struct shash_desc *desc, u8 *out)
+{
+	sha1_final(SHA1_CTX(desc), out);
+	return 0;
+}
+
+static int crypto_sha1_digest(struct shash_desc *desc,
+			      const u8 *data, unsigned int len, u8 *out)
+{
+	sha1(data, len, out);
+	return 0;
+}
+
+static int crypto_sha1_export(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha1_export(SHA1_CTX(desc), out);
+}
+
+static int crypto_sha1_import(struct shash_desc *desc, const void *in)
+{
+	return __crypto_sha1_import(SHA1_CTX(desc), in);
+}
+
+static int crypto_sha1_export_core(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha1_export_core(SHA1_CTX(desc), out);
+}
+
+static int crypto_sha1_import_core(struct shash_desc *desc, const void *in)
+{
+	return __crypto_sha1_import_core(SHA1_CTX(desc), in);
+}
+
+#define HMAC_SHA1_KEY(tfm) ((struct hmac_sha1_key *)crypto_shash_ctx(tfm))
+#define HMAC_SHA1_CTX(desc) ((struct hmac_sha1_ctx *)shash_desc_ctx(desc))
+
+static int crypto_hmac_sha1_setkey(struct crypto_shash *tfm,
+				   const u8 *raw_key, unsigned int keylen)
+{
+	hmac_sha1_preparekey(HMAC_SHA1_KEY(tfm), raw_key, keylen);
+	return 0;
+}
+
+static int crypto_hmac_sha1_init(struct shash_desc *desc)
+{
+	hmac_sha1_init(HMAC_SHA1_CTX(desc), HMAC_SHA1_KEY(desc->tfm));
+	return 0;
+}
+
+static int crypto_hmac_sha1_update(struct shash_desc *desc,
+				   const u8 *data, unsigned int len)
+{
+	hmac_sha1_update(HMAC_SHA1_CTX(desc), data, len);
+	return 0;
+}
+
+static int crypto_hmac_sha1_final(struct shash_desc *desc, u8 *out)
+{
+	hmac_sha1_final(HMAC_SHA1_CTX(desc), out);
+	return 0;
+}
+
+static int crypto_hmac_sha1_digest(struct shash_desc *desc,
+				   const u8 *data, unsigned int len, u8 *out)
+{
+	hmac_sha1(HMAC_SHA1_KEY(desc->tfm), data, len, out);
+	return 0;
+}
+
+static int crypto_hmac_sha1_export(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha1_export(&HMAC_SHA1_CTX(desc)->sha_ctx, out);
+}
+
+static int crypto_hmac_sha1_import(struct shash_desc *desc, const void *in)
+{
+	struct hmac_sha1_ctx *ctx = HMAC_SHA1_CTX(desc);
+
+	ctx->ostate = HMAC_SHA1_KEY(desc->tfm)->ostate;
+	return __crypto_sha1_import(&ctx->sha_ctx, in);
+}
+
+static int crypto_hmac_sha1_export_core(struct shash_desc *desc, void *out)
+{
+	return __crypto_sha1_export_core(&HMAC_SHA1_CTX(desc)->sha_ctx, out);
+}
+
+static int crypto_hmac_sha1_import_core(struct shash_desc *desc, const void *in)
+{
+	struct hmac_sha1_ctx *ctx = HMAC_SHA1_CTX(desc);
+
+	ctx->ostate = HMAC_SHA1_KEY(desc->tfm)->ostate;
+	return __crypto_sha1_import_core(&ctx->sha_ctx, in);
+}
+
+static struct shash_alg algs[] = {
+	{
+		.base.cra_name		= "sha1",
+		.base.cra_driver_name	= "sha1-lib",
+		.base.cra_priority	= 300,
+		.base.cra_blocksize	= SHA1_BLOCK_SIZE,
+		.base.cra_module	= THIS_MODULE,
+		.digestsize		= SHA1_DIGEST_SIZE,
+		.init			= crypto_sha1_init,
+		.update			= crypto_sha1_update,
+		.final			= crypto_sha1_final,
+		.digest			= crypto_sha1_digest,
+		.export			= crypto_sha1_export,
+		.import			= crypto_sha1_import,
+		.export_core		= crypto_sha1_export_core,
+		.import_core		= crypto_sha1_import_core,
+		.descsize		= sizeof(struct sha1_ctx),
+		.statesize		= SHA1_SHASH_STATE_SIZE,
+	},
+	{
+		.base.cra_name		= "hmac(sha1)",
+		.base.cra_driver_name	= "hmac-sha1-lib",
+		.base.cra_priority	= 300,
+		.base.cra_blocksize	= SHA1_BLOCK_SIZE,
+		.base.cra_ctxsize	= sizeof(struct hmac_sha1_key),
+		.base.cra_module	= THIS_MODULE,
+		.digestsize		= SHA1_DIGEST_SIZE,
+		.setkey			= crypto_hmac_sha1_setkey,
+		.init			= crypto_hmac_sha1_init,
+		.update			= crypto_hmac_sha1_update,
+		.final			= crypto_hmac_sha1_final,
+		.digest			= crypto_hmac_sha1_digest,
+		.export			= crypto_hmac_sha1_export,
+		.import			= crypto_hmac_sha1_import,
+		.export_core		= crypto_hmac_sha1_export_core,
+		.import_core		= crypto_hmac_sha1_import_core,
+		.descsize		= sizeof(struct hmac_sha1_ctx),
+		.statesize		= SHA1_SHASH_STATE_SIZE,
+	},
+};
+
+static int __init crypto_sha1_mod_init(void)
+{
+	return crypto_register_shashes(algs, ARRAY_SIZE(algs));
+}
+module_init(crypto_sha1_mod_init);
+
+static void __exit crypto_sha1_mod_exit(void)
+{
+	crypto_unregister_shashes(algs, ARRAY_SIZE(algs));
+}
+module_exit(crypto_sha1_mod_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Crypto API support for SHA-1 and HMAC-SHA1");
+
+MODULE_ALIAS_CRYPTO("sha1");
+MODULE_ALIAS_CRYPTO("sha1-lib");
+MODULE_ALIAS_CRYPTO("hmac(sha1)");
+MODULE_ALIAS_CRYPTO("hmac-sha1-lib");