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/Makefile | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 lib/tests/Makefile (limited to 'lib/tests/Makefile') diff --git a/lib/tests/Makefile b/lib/tests/Makefile new file mode 100644 index 000000000..3cac3b63a --- /dev/null +++ b/lib/tests/Makefile @@ -0,0 +1,61 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Makefile for tests of kernel library functions. + +# KUnit tests +CFLAGS_bitfield_kunit.o := $(DISABLE_STRUCTLEAK_PLUGIN) +obj-$(CONFIG_BASE64_KUNIT) += base64_kunit.o +obj-$(CONFIG_BITOPS_KUNIT) += bitops_kunit.o +obj-$(CONFIG_BITFIELD_KUNIT) += bitfield_kunit.o +obj-$(CONFIG_BITS_TEST) += test_bits.o +obj-$(CONFIG_SHDI3_KUNIT_TEST) += shdi3_kunit.o +obj-$(CONFIG_BLACKHOLE_DEV_KUNIT_TEST) += blackhole_dev_kunit.o +obj-$(CONFIG_CHECKSUM_KUNIT) += checksum_kunit.o +obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o +obj-$(CONFIG_CPUMASK_KUNIT_TEST) += cpumask_kunit.o +obj-$(CONFIG_FFS_KUNIT_TEST) += ffs_kunit.o +CFLAGS_fortify_kunit.o += $(call cc-disable-warning, unsequenced) +CFLAGS_fortify_kunit.o += $(call cc-disable-warning, stringop-overread) +CFLAGS_fortify_kunit.o += $(call cc-disable-warning, stringop-truncation) +CFLAGS_fortify_kunit.o += $(DISABLE_STRUCTLEAK_PLUGIN) +obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o +CFLAGS_test_fprobe.o += $(CC_FLAGS_FTRACE) +obj-$(CONFIG_FPROBE_SANITY_TEST) += test_fprobe.o +obj-$(CONFIG_GLOB_KUNIT_TEST) += glob_kunit.o +obj-$(CONFIG_HASHTABLE_KUNIT_TEST) += hashtable_test.o +obj-$(CONFIG_HASH_KUNIT_TEST) += test_hash.o +obj-$(CONFIG_TEST_IOV_ITER) += kunit_iov_iter.o +obj-$(CONFIG_IS_SIGNED_TYPE_KUNIT_TEST) += is_signed_type_kunit.o +obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o +obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o +obj-$(CONFIG_LIST_PRIVATE_KUNIT_TEST) += list-private-test.o +obj-$(CONFIG_KFIFO_KUNIT_TEST) += kfifo_kunit.o +obj-$(CONFIG_TEST_LIST_SORT) += test_list_sort.o +obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o +obj-$(CONFIG_LIVEUPDATE_TEST) += liveupdate.o + +CFLAGS_longest_symbol_kunit.o += $(call cc-disable-warning, missing-prototypes) +obj-$(CONFIG_LONGEST_SYM_KUNIT_TEST) += longest_symbol_kunit.o + +obj-$(CONFIG_MEMCPY_KUNIT_TEST) += memcpy_kunit.o +obj-$(CONFIG_MIN_HEAP_KUNIT_TEST) += min_heap_kunit.o +CFLAGS_overflow_kunit.o = $(call cc-disable-warning, tautological-constant-out-of-range-compare) +obj-$(CONFIG_OVERFLOW_KUNIT_TEST) += overflow_kunit.o +obj-$(CONFIG_PRANDOM_KUNIT_TEST) += random32_kunit.o +obj-$(CONFIG_PRINTF_KUNIT_TEST) += printf_kunit.o +obj-$(CONFIG_RANDSTRUCT_KUNIT_TEST) += randstruct_kunit.o +obj-$(CONFIG_SCANF_KUNIT_TEST) += scanf_kunit.o +obj-$(CONFIG_SEQ_BUF_KUNIT_TEST) += seq_buf_kunit.o +obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o +obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o +obj-$(CONFIG_TEST_SORT) += test_sort.o +CFLAGS_stackinit_kunit.o += $(call cc-disable-warning, switch-unreachable) +obj-$(CONFIG_STACKINIT_KUNIT_TEST) += stackinit_kunit.o +obj-$(CONFIG_STRING_KUNIT_TEST) += string_kunit.o +obj-$(CONFIG_STRING_HELPERS_KUNIT_TEST) += string_helpers_kunit.o +obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o +obj-$(CONFIG_UTIL_MACROS_KUNIT) += util_macros_kunit.o +obj-$(CONFIG_RATELIMIT_KUNIT_TEST) += test_ratelimit.o +obj-$(CONFIG_UUID_KUNIT_TEST) += uuid_kunit.o + +obj-$(CONFIG_TEST_RUNTIME_MODULE) += module/ -- cgit v1.3.1