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 --- lib/crypto/arc4.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 lib/crypto/arc4.c (limited to 'lib/crypto/arc4.c') diff --git a/lib/crypto/arc4.c b/lib/crypto/arc4.c new file mode 100644 index 000000000..4e950e1e6 --- /dev/null +++ b/lib/crypto/arc4.c @@ -0,0 +1,76 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Cryptographic API + * + * ARC4 Cipher Algorithm + * + * Jon Oberheide + */ + +#include +#include +#include + +int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len) +{ + int i, j = 0, k = 0; + + ctx->x = 1; + ctx->y = 0; + + for (i = 0; i < 256; i++) + ctx->S[i] = i; + + for (i = 0; i < 256; i++) { + u32 a = ctx->S[i]; + + j = (j + in_key[k] + a) & 0xff; + ctx->S[i] = ctx->S[j]; + ctx->S[j] = a; + if (++k >= key_len) + k = 0; + } + + return 0; +} +EXPORT_SYMBOL(arc4_setkey); + +void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len) +{ + u32 *const S = ctx->S; + u32 x, y, a, b; + u32 ty, ta, tb; + + if (len == 0) + return; + + x = ctx->x; + y = ctx->y; + + a = S[x]; + y = (y + a) & 0xff; + b = S[y]; + + do { + S[y] = a; + a = (a + b) & 0xff; + S[x] = b; + x = (x + 1) & 0xff; + ta = S[x]; + ty = (y + ta) & 0xff; + tb = S[ty]; + *out++ = *in++ ^ S[a]; + if (--len == 0) + break; + y = ty; + a = ta; + b = tb; + } while (true); + + ctx->x = x; + ctx->y = y; +} +EXPORT_SYMBOL(arc4_crypt); + +MODULE_DESCRIPTION("ARC4 Cipher Algorithm"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1