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/lzo.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 crypto/lzo.c (limited to 'crypto/lzo.c') diff --git a/crypto/lzo.c b/crypto/lzo.c new file mode 100644 index 000000000..d43242b24 --- /dev/null +++ b/crypto/lzo.c @@ -0,0 +1,101 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Cryptographic API. + */ + +#include +#include +#include +#include +#include + +static void *lzo_alloc_ctx(void) +{ + void *ctx; + + ctx = kvmalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL); + if (!ctx) + return ERR_PTR(-ENOMEM); + + return ctx; +} + +static void lzo_free_ctx(void *ctx) +{ + kvfree(ctx); +} + +static int __lzo_compress(const u8 *src, unsigned int slen, + u8 *dst, unsigned int *dlen, void *ctx) +{ + size_t tmp_len = *dlen; /* size_t(ulong) <-> uint on 64 bit */ + int err; + + err = lzo1x_1_compress_safe(src, slen, dst, &tmp_len, ctx); + + if (err != LZO_E_OK) + return -EINVAL; + + *dlen = tmp_len; + return 0; +} + +static int lzo_scompress(struct crypto_scomp *tfm, const u8 *src, + unsigned int slen, u8 *dst, unsigned int *dlen, + void *ctx) +{ + return __lzo_compress(src, slen, dst, dlen, ctx); +} + +static int __lzo_decompress(const u8 *src, unsigned int slen, + u8 *dst, unsigned int *dlen) +{ + int err; + size_t tmp_len = *dlen; /* size_t(ulong) <-> uint on 64 bit */ + + err = lzo1x_decompress_safe(src, slen, dst, &tmp_len); + + if (err != LZO_E_OK) + return -EINVAL; + + *dlen = tmp_len; + return 0; +} + +static int lzo_sdecompress(struct crypto_scomp *tfm, const u8 *src, + unsigned int slen, u8 *dst, unsigned int *dlen, + void *ctx) +{ + return __lzo_decompress(src, slen, dst, dlen); +} + +static struct scomp_alg scomp = { + .streams = { + .alloc_ctx = lzo_alloc_ctx, + .free_ctx = lzo_free_ctx, + }, + .compress = lzo_scompress, + .decompress = lzo_sdecompress, + .base = { + .cra_name = "lzo", + .cra_driver_name = "lzo-scomp", + .cra_module = THIS_MODULE, + } +}; + +static int __init lzo_mod_init(void) +{ + return crypto_register_scomp(&scomp); +} + +static void __exit lzo_mod_fini(void) +{ + crypto_unregister_scomp(&scomp); +} + +module_init(lzo_mod_init); +module_exit(lzo_mod_fini); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("LZO Compression Algorithm"); +MODULE_ALIAS_CRYPTO("lzo"); -- cgit v1.3.1