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/tests/test_bits.c | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 lib/tests/test_bits.c (limited to 'lib/tests/test_bits.c') diff --git a/lib/tests/test_bits.c b/lib/tests/test_bits.c new file mode 100644 index 000000000..ab88e50d2 --- /dev/null +++ b/lib/tests/test_bits.c @@ -0,0 +1,159 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Test cases for functions and macros in bits.h + */ + +#include +#include +#include + +#define assert_type(t, x) _Generic(x, t: x, default: 0) + +static_assert(assert_type(u8, BIT_U8(0)) == 1u); +static_assert(assert_type(u16, BIT_U16(0)) == 1u); +static_assert(assert_type(u32, BIT_U32(0)) == 1u); +static_assert(assert_type(u64, BIT_U64(0)) == 1ull); + +static_assert(assert_type(u8, BIT_U8(7)) == 0x80u); +static_assert(assert_type(u16, BIT_U16(15)) == 0x8000u); +static_assert(assert_type(u32, BIT_U32(31)) == 0x80000000u); +static_assert(assert_type(u64, BIT_U64(63)) == 0x8000000000000000ull); + +static_assert(assert_type(unsigned long, GENMASK(31, 0)) == U32_MAX); +static_assert(assert_type(unsigned long long, GENMASK_ULL(63, 0)) == U64_MAX); +static_assert(assert_type(u8, GENMASK_U8(7, 0)) == U8_MAX); +static_assert(assert_type(u16, GENMASK_U16(15, 0)) == U16_MAX); +static_assert(assert_type(u32, GENMASK_U32(31, 0)) == U32_MAX); +static_assert(assert_type(u64, GENMASK_U64(63, 0)) == U64_MAX); + +/* FIXME: add a test case written in asm for GENMASK() and GENMASK_ULL() */ + +static void __genmask_test(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 1ul, __GENMASK(0, 0)); + KUNIT_EXPECT_EQ(test, 3ul, __GENMASK(1, 0)); + KUNIT_EXPECT_EQ(test, 6ul, __GENMASK(2, 1)); + KUNIT_EXPECT_EQ(test, 0xFFFFFFFFul, __GENMASK(31, 0)); +} + +static void __genmask_ull_test(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 1ull, __GENMASK_ULL(0, 0)); + KUNIT_EXPECT_EQ(test, 3ull, __GENMASK_ULL(1, 0)); + KUNIT_EXPECT_EQ(test, 0x000000ffffe00000ull, __GENMASK_ULL(39, 21)); + KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, __GENMASK_ULL(63, 0)); +} + +static void genmask_test(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 1ul, GENMASK(0, 0)); + KUNIT_EXPECT_EQ(test, 3ul, GENMASK(1, 0)); + KUNIT_EXPECT_EQ(test, 6ul, GENMASK(2, 1)); + KUNIT_EXPECT_EQ(test, 0xFFFFFFFFul, GENMASK(31, 0)); + + KUNIT_EXPECT_EQ(test, 1u, GENMASK_U8(0, 0)); + KUNIT_EXPECT_EQ(test, 3u, GENMASK_U16(1, 0)); + KUNIT_EXPECT_EQ(test, 0x10000, GENMASK_U32(16, 16)); + +#ifdef TEST_GENMASK_FAILURES + /* these should fail compilation */ + GENMASK(0, 1); + GENMASK(0, 10); + GENMASK(9, 10); + + GENMASK_U32(0, 31); + GENMASK_U64(64, 0); + GENMASK_U32(32, 0); + GENMASK_U16(16, 0); + GENMASK_U8(8, 0); +#endif + + +} + +static void genmask_ull_test(struct kunit *test) +{ + KUNIT_EXPECT_EQ(test, 1ull, GENMASK_ULL(0, 0)); + KUNIT_EXPECT_EQ(test, 3ull, GENMASK_ULL(1, 0)); + KUNIT_EXPECT_EQ(test, 0x000000ffffe00000ull, GENMASK_ULL(39, 21)); + KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, GENMASK_ULL(63, 0)); + +#ifdef TEST_GENMASK_FAILURES + /* these should fail compilation */ + GENMASK_ULL(0, 1); + GENMASK_ULL(0, 10); + GENMASK_ULL(9, 10); +#endif +} + +static void genmask_u128_test(struct kunit *test) +{ +#ifdef CONFIG_ARCH_SUPPORTS_INT128 + /* Below 64 bit masks */ + KUNIT_EXPECT_EQ(test, 0x0000000000000001ull, GENMASK_U128(0, 0)); + KUNIT_EXPECT_EQ(test, 0x0000000000000003ull, GENMASK_U128(1, 0)); + KUNIT_EXPECT_EQ(test, 0x0000000000000006ull, GENMASK_U128(2, 1)); + KUNIT_EXPECT_EQ(test, 0x00000000ffffffffull, GENMASK_U128(31, 0)); + KUNIT_EXPECT_EQ(test, 0x000000ffffe00000ull, GENMASK_U128(39, 21)); + KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, GENMASK_U128(63, 0)); + + /* Above 64 bit masks - only 64 bit portion can be validated once */ + KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, GENMASK_U128(64, 0) >> 1); + KUNIT_EXPECT_EQ(test, 0x00000000ffffffffull, GENMASK_U128(81, 50) >> 50); + KUNIT_EXPECT_EQ(test, 0x0000000000ffffffull, GENMASK_U128(87, 64) >> 64); + KUNIT_EXPECT_EQ(test, 0x0000000000ff0000ull, GENMASK_U128(87, 80) >> 64); + + KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, GENMASK_U128(127, 0) >> 64); + KUNIT_EXPECT_EQ(test, 0xffffffffffffffffull, (u64)GENMASK_U128(127, 0)); + KUNIT_EXPECT_EQ(test, 0x0000000000000003ull, GENMASK_U128(127, 126) >> 126); + KUNIT_EXPECT_EQ(test, 0x0000000000000001ull, GENMASK_U128(127, 127) >> 127); +#ifdef TEST_GENMASK_FAILURES + /* these should fail compilation */ + GENMASK_U128(0, 1); + GENMASK_U128(0, 10); + GENMASK_U128(9, 10); +#endif /* TEST_GENMASK_FAILURES */ +#endif /* CONFIG_ARCH_SUPPORTS_INT128 */ +} + +static void genmask_input_check_test(struct kunit *test) +{ + unsigned int x, y; + int z, w; + + /* Unknown input */ + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(x, 0)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(0, x)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(x, y)); + + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(z, 0)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(0, z)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(z, w)); + + /* Valid input */ + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(1, 1)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(39, 21)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(100, 80)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(110, 65)); + KUNIT_EXPECT_EQ(test, 0, GENMASK_INPUT_CHECK(127, 0)); +} + + +static struct kunit_case bits_test_cases[] = { + KUNIT_CASE(__genmask_test), + KUNIT_CASE(__genmask_ull_test), + KUNIT_CASE(genmask_test), + KUNIT_CASE(genmask_ull_test), + KUNIT_CASE(genmask_u128_test), + KUNIT_CASE(genmask_input_check_test), + {} +}; + +static struct kunit_suite bits_test_suite = { + .name = "bits-test", + .test_cases = bits_test_cases, +}; +kunit_test_suite(bits_test_suite); + +MODULE_DESCRIPTION("Test cases for functions and macros in bits.h"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1