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 --- net/mptcp/crypto_test.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 net/mptcp/crypto_test.c (limited to 'net/mptcp/crypto_test.c') diff --git a/net/mptcp/crypto_test.c b/net/mptcp/crypto_test.c new file mode 100644 index 000000000..220414e5c --- /dev/null +++ b/net/mptcp/crypto_test.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +#include "protocol.h" + +struct test_case { + char *key; + char *msg; + char *result; +}; + +/* we can't reuse RFC 4231 test vectors, as we have constraint on the + * input and key size. + */ +static struct test_case tests[] = { + { + .key = "0b0b0b0b0b0b0b0b", + .msg = "48692054", + .result = "8385e24fb4235ac37556b6b886db106284a1da671699f46db1f235ec622dcafa", + }, + { + .key = "aaaaaaaaaaaaaaaa", + .msg = "dddddddd", + .result = "2c5e219164ff1dca1c4a92318d847bb6b9d44492984e1eb71aff9022f71046e9", + }, + { + .key = "0102030405060708", + .msg = "cdcdcdcd", + .result = "e73b9ba9969969cefb04aa0d6df18ec2fcc075b6f23b4d8c4da736a5dbbc6e7d", + }, +}; + +static void mptcp_crypto_test_basic(struct kunit *test) +{ + char hmac[32], hmac_hex[65]; + u32 nonce1, nonce2; + u64 key1, key2; + u8 msg[8]; + int i, j; + + for (i = 0; i < ARRAY_SIZE(tests); ++i) { + /* mptcp hmap will convert to be before computing the hmac */ + key1 = be64_to_cpu(*((__be64 *)&tests[i].key[0])); + key2 = be64_to_cpu(*((__be64 *)&tests[i].key[8])); + nonce1 = be32_to_cpu(*((__be32 *)&tests[i].msg[0])); + nonce2 = be32_to_cpu(*((__be32 *)&tests[i].msg[4])); + + put_unaligned_be32(nonce1, &msg[0]); + put_unaligned_be32(nonce2, &msg[4]); + + mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac); + for (j = 0; j < 32; ++j) + sprintf(&hmac_hex[j << 1], "%02x", hmac[j] & 0xff); + hmac_hex[64] = 0; + + KUNIT_EXPECT_STREQ(test, &hmac_hex[0], tests[i].result); + } +} + +static struct kunit_case mptcp_crypto_test_cases[] = { + KUNIT_CASE(mptcp_crypto_test_basic), + {} +}; + +static struct kunit_suite mptcp_crypto_suite = { + .name = "mptcp-crypto", + .test_cases = mptcp_crypto_test_cases, +}; + +kunit_test_suite(mptcp_crypto_suite); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("KUnit tests for MPTCP Crypto"); -- cgit v1.3.1