From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug 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 Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- crypto/xxhash_generic.c | 106 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 crypto/xxhash_generic.c (limited to 'crypto/xxhash_generic.c') diff --git a/crypto/xxhash_generic.c b/crypto/xxhash_generic.c new file mode 100644 index 000000000..175bb7ae0 --- /dev/null +++ b/crypto/xxhash_generic.c @@ -0,0 +1,106 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include + +#define XXHASH64_BLOCK_SIZE 32 +#define XXHASH64_DIGEST_SIZE 8 + +struct xxhash64_tfm_ctx { + u64 seed; +}; + +struct xxhash64_desc_ctx { + struct xxh64_state xxhstate; +}; + +static int xxhash64_setkey(struct crypto_shash *tfm, const u8 *key, + unsigned int keylen) +{ + struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(tfm); + + if (keylen != sizeof(tctx->seed)) + return -EINVAL; + tctx->seed = get_unaligned_le64(key); + return 0; +} + +static int xxhash64_init(struct shash_desc *desc) +{ + struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm); + struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc); + + xxh64_reset(&dctx->xxhstate, tctx->seed); + + return 0; +} + +static int xxhash64_update(struct shash_desc *desc, const u8 *data, + unsigned int length) +{ + struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc); + + xxh64_update(&dctx->xxhstate, data, length); + + return 0; +} + +static int xxhash64_final(struct shash_desc *desc, u8 *out) +{ + struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc); + + put_unaligned_le64(xxh64_digest(&dctx->xxhstate), out); + + return 0; +} + +static int xxhash64_digest(struct shash_desc *desc, const u8 *data, + unsigned int length, u8 *out) +{ + struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm); + + put_unaligned_le64(xxh64(data, length, tctx->seed), out); + + return 0; +} + +static struct shash_alg alg = { + .digestsize = XXHASH64_DIGEST_SIZE, + .setkey = xxhash64_setkey, + .init = xxhash64_init, + .update = xxhash64_update, + .final = xxhash64_final, + .digest = xxhash64_digest, + .descsize = sizeof(struct xxhash64_desc_ctx), + .base = { + .cra_name = "xxhash64", + .cra_driver_name = "xxhash64-generic", + .cra_priority = 100, + .cra_flags = CRYPTO_ALG_OPTIONAL_KEY, + .cra_blocksize = XXHASH64_BLOCK_SIZE, + .cra_ctxsize = sizeof(struct xxhash64_tfm_ctx), + .cra_module = THIS_MODULE, + } +}; + +static int __init xxhash_mod_init(void) +{ + return crypto_register_shash(&alg); +} + +static void __exit xxhash_mod_fini(void) +{ + crypto_unregister_shash(&alg); +} + +module_init(xxhash_mod_init); +module_exit(xxhash_mod_fini); + +MODULE_AUTHOR("Nikolay Borisov "); +MODULE_DESCRIPTION("xxhash calculations wrapper for lib/xxhash.c"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS_CRYPTO("xxhash64"); +MODULE_ALIAS_CRYPTO("xxhash64-generic"); -- cgit v1.3.1