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/arc4.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 crypto/arc4.c (limited to 'crypto/arc4.c') diff --git a/crypto/arc4.c b/crypto/arc4.c new file mode 100644 index 000000000..160801811 --- /dev/null +++ b/crypto/arc4.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Cryptographic API + * + * ARC4 Cipher Algorithm + * + * Jon Oberheide + */ + +#include +#include +#include +#include +#include +#include + +#define ARC4_ALIGN __alignof__(struct arc4_ctx) + +static int crypto_arc4_setkey(struct crypto_lskcipher *tfm, const u8 *in_key, + unsigned int key_len) +{ + struct arc4_ctx *ctx = crypto_lskcipher_ctx(tfm); + + return arc4_setkey(ctx, in_key, key_len); +} + +static int crypto_arc4_crypt(struct crypto_lskcipher *tfm, const u8 *src, + u8 *dst, unsigned nbytes, u8 *siv, u32 flags) +{ + struct arc4_ctx *ctx = crypto_lskcipher_ctx(tfm); + + if (!(flags & CRYPTO_LSKCIPHER_FLAG_CONT)) + memcpy(siv, ctx, sizeof(*ctx)); + + ctx = (struct arc4_ctx *)siv; + + arc4_crypt(ctx, dst, src, nbytes); + return 0; +} + +static int crypto_arc4_init(struct crypto_lskcipher *tfm) +{ + pr_warn_ratelimited("\"%s\" (%ld) uses obsolete ecb(arc4) skcipher\n", + current->comm, (unsigned long)current->pid); + + return 0; +} + +static struct lskcipher_alg arc4_alg = { + .co.base.cra_name = "arc4", + .co.base.cra_driver_name = "arc4-generic", + .co.base.cra_priority = 100, + .co.base.cra_blocksize = ARC4_BLOCK_SIZE, + .co.base.cra_ctxsize = sizeof(struct arc4_ctx), + .co.base.cra_alignmask = ARC4_ALIGN - 1, + .co.base.cra_module = THIS_MODULE, + .co.min_keysize = ARC4_MIN_KEY_SIZE, + .co.max_keysize = ARC4_MAX_KEY_SIZE, + .co.statesize = sizeof(struct arc4_ctx), + .setkey = crypto_arc4_setkey, + .encrypt = crypto_arc4_crypt, + .decrypt = crypto_arc4_crypt, + .init = crypto_arc4_init, +}; + +static int __init arc4_init(void) +{ + return crypto_register_lskcipher(&arc4_alg); +} + +static void __exit arc4_exit(void) +{ + crypto_unregister_lskcipher(&arc4_alg); +} + +module_init(arc4_init); +module_exit(arc4_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("ARC4 Cipher Algorithm"); +MODULE_AUTHOR("Jon Oberheide "); +MODULE_ALIAS_CRYPTO("ecb(arc4)"); -- cgit v1.3.1